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949 lines
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949 lines
41 KiB
Plaintext
// Copyright (C) 2016 The Qt Company Ltd.
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// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
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/*!
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\page tutorials-addressbook.html
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\title Address Book Tutorial
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\ingroup examples-layout
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\brief An introduction to GUI programming, showing how to put together a
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simple yet fully-functioning application.
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This tutorial is an introduction to GUI programming with the Qt
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cross-platform framework.
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\image addressbook-tutorial-screenshot.png
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\omit
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It doesn't cover everything; the emphasis is on teaching the programming
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philosophy of GUI programming, and Qt's features are introduced as needed.
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Some commonly used features are never used in this tutorial.
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\endomit
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In this tutorial, you will learn about some of the basic
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components of Qt, including:
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\list
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\li Widgets and layout managers
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\li Container classes
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\li Signals and slots
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\li Input and output devices
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\endlist
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Tutorial contents:
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\list 1
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\li \l{tutorials/addressbook/part1}{Designing the User Interface}
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\li \l{tutorials/addressbook/part2}{Adding Addresses}
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\li \l{tutorials/addressbook/part3}{Navigating between Entries}
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\li \l{tutorials/addressbook/part4}{Editing and Removing Addresses}
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\li \l{tutorials/addressbook/part5}{Adding a Find Function}
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\li \l{tutorials/addressbook/part6}{Loading and Saving}
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\li \l{tutorials/addressbook/part7}{Additional Features}
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\endlist
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The tutorial source code is located in \c{tutorials/addressbook}.
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Although this little application does not look much like a
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fully-fledged modern GUI application, it uses many of the basic
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elements that are used in more complex applications. After you
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have worked through this tutorial, we recommend reading the
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\l{mainwindows/application}{Application} example, which presents a
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small GUI application, with menus, toolbars, a status bar, and so
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on.
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*/
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/*!
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\example tutorials/addressbook/part1
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\title Part 1 - Designing the User Interface
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\brief Describes how to code the user interface of the Address Book Example.
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This first part covers the design of the basic graphical user
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interface (GUI) for our address book application.
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The first step in creating a GUI program is to design the user
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interface. Here the our goal is to set up the labels and input
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fields to implement a basic address book. The figure below is a
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screenshot of the expected output.
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\image addressbook-tutorial-part1-screenshot.png
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We require two QLabel objects, \c nameLabel and \c addressLabel, as well
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as two input fields, a QLineEdit object, \c nameLine, and a QTextEdit
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object, \c addressText, to enable the user to enter a contact's name and
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address. The widgets used and their positions are shown in the figure
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below.
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\image addressbook-tutorial-part1-labeled-screenshot.png
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There are three files used to implement this address book:
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\list
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\li \c{addressbook.h} - the definition file for the \c AddressBook
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class,
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\li \c{addressbook.cpp} - the implementation file for the
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\c AddressBook class, and
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\li \c{main.cpp} - the file containing a \c main() function, with
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an instance of \c AddressBook.
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\endlist
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\section1 Qt Programming - Subclassing
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When writing Qt programs, we usually subclass Qt objects to add
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functionality. This is one of the essential concepts behind creating
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custom widgets or collections of standard widgets. Subclassing to
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extend or change the behavior of a widget has the following advantages:
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\list
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\li We can write implementations of virtual or pure virtual functions to
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obtain exactly what we need, falling back on the base class's implementation
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when necessary.
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\li It allows us to encapsulate parts of the user interface within a class,
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so that the other parts of the application don't need to know about the
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individual widgets in the user interface.
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\li The subclass can be used to create multiple custom widgets in the same
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application or library, and the code for the subclass can be reused in other
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projects.
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\endlist
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Since Qt does not provide a specific address book widget, we subclass a
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standard Qt widget class and add features to it. The \c AddressBook class
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we create in this tutorial can be reused in situations where a basic address
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book widget is needed.
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\section1 Defining the AddressBook Class
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The \c{tutorials/addressbook/part1/addressbook.h} file is
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used to define the \c AddressBook class.
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We start by defining \c AddressBook as a QWidget subclass and declaring
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a constructor. We also use the Q_OBJECT macro to indicate that the class
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uses internationalization and Qt's signals and slots features, even
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if we do not use all of these features at this stage.
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\snippet tutorials/addressbook/part1/addressbook.h class definition
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The class holds declarations of \c nameLine and \c addressText,
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the private instances of QLineEdit and QTextEdit mentioned
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earlier. The data stored in \c nameLine and \c addressText will
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be needed for many of the address book functions.
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We don't include declarations of the QLabel objects we will use
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because we will not need to reference them once they have been
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created. The way Qt tracks the ownership of objects is explained
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in the next section.
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The Q_OBJECT macro itself implements some of the more advanced features of Qt.
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For now, it is useful to think of the Q_OBJECT macro as a shortcut which allows
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us to use the \l{QObject::}{tr()} and \l{QObject::}{connect()} functions.
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We have now completed the \c addressbook.h file and we move on to
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implement the corresponding \c addressbook.cpp file.
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\section1 Implementing the AddressBook Class
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The constructor of \c AddressBook accepts a QWidget parameter, \a parent.
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By convention, we pass this parameter to the base class's constructor.
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This concept of ownership, where a parent can have one or more children,
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is useful for grouping widgets in Qt. For example, if you delete a parent,
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all of its children will be deleted as well.
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\snippet tutorials/addressbook/part1/addressbook.cpp constructor and input fields
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In this constructor, the QLabel objects \c nameLabel and \c
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addressLabel are instantiated, as well as \c nameLine and \c
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addressText. The \l{QObject::tr()}{tr()} function returns a
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translated version of the string, if there is one
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available. Otherwise it returns the string itself. This function
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marks its QString parameter as one that should be translated into
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other languages. It should be used wherever a translatable string
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appears.
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When programming with Qt, it is useful to know how layouts work.
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Qt provides three main layout classes: QHBoxLayout, QVBoxLayout
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and QGridLayout to handle the positioning of widgets.
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\image addressbook-tutorial-part1-labeled-layout.png
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We use a QGridLayout to position our labels and input fields in a
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structured manner. QGridLayout divides the available space into a grid and
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places widgets in the cells we specify with row and column numbers. The
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diagram above shows the layout cells and the position of our widgets, and
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we specify this arrangement using the following code:
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\snippet tutorials/addressbook/part1/addressbook.cpp layout
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Notice that \c addressLabel is positioned using Qt::AlignTop as an
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additional argument. This is to make sure it is not vertically centered in
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cell (1,0). For a basic overview on Qt Layouts, refer to the
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\l{Layout Management} documentation.
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In order to install the layout object onto the widget, we have to invoke
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the widget's \l{QWidget::setLayout()}{setLayout()} function:
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\snippet tutorials/addressbook/part1/addressbook.cpp setting the layout
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Lastly, we set the widget's title to "Simple Address Book".
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\section1 Running the Application
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A separate file, \c main.cpp, is used for the \c main() function. Within
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this function, we instantiate a QApplication object, \c app. QApplication
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is responsible for various application-wide resources, such as the default
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font and cursor, and for running an event loop. Hence, there is always one
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QApplication object in every GUI application using Qt.
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\snippet tutorials/addressbook/part1/main.cpp main function
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We construct a new \c AddressBook widget on the stack and invoke
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its \l{QWidget::show()}{show()} function to display it.
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However, the widget will not be shown until the application's event loop
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is started. We start the event loop by calling the application's
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\l{QApplication::}{exec()} function; the result returned by this function
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is used as the return value from the \c main() function. At this point,
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it becomes apparent why we instantiated \c AddressBook on the stack: It
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will now go out of scope. Therefore, \c AddressBook and all its child widgets
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will be deleted, thus preventing memory leaks.
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*/
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/*!
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\example tutorials/addressbook/part2
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\title Part 2 - Adding Addresses
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\brief Describes the code for inserting records in the Address Book Example.
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The next step in creating the address book is to implement some
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user interactions.
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\image addressbook-tutorial-part2-add-contact.png
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We will provide a push button that the user can click to add a new contact.
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Also, some form of data structure is needed to store these contacts in an
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organized way.
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\section1 Defining the AddressBook Class
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Now that we have the labels and input fields set up, we add push buttons to
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complete the process of adding a contact. This means that our
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\c addressbook.h file now has three QPushButton objects declared and three
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corresponding public slots.
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\snippet tutorials/addressbook/part2/addressbook.h slots
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A slot is a function that responds to a particular signal. We will discuss
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this concept in further detail when implementing the \c AddressBook class.
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However, for an overview of Qt's signals and slots concept, you can refer
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to the \l{Signals and Slots} document.
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Three QPushButton objects (\c addButton, \c submitButton, and
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\c cancelButton) are now included in our private variable declarations,
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along with \c nameLine and \c addressText.
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\snippet tutorials/addressbook/part2/addressbook.h pushbutton declaration
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We need a container to store our address book contacts, so that we can
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traverse and display them. A QMap object, \c contacts, is used for this
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purpose as it holds a key-value pair: the contact's name as the \e key,
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and the contact's address as the \e{value}.
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\snippet tutorials/addressbook/part2/addressbook.h remaining private variables
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We also declare two private QString objects, \c oldName and \c oldAddress.
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These objects are needed to hold the name and address of the contact that
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was last displayed, before the user clicked \uicontrol Add. So, when the user clicks
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\uicontrol Cancel, we can revert to displaying the details of the last contact.
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\section1 Implementing the AddressBook Class
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Within the constructor of \c AddressBook, we set the \c nameLine and
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\c addressText to read-only, so that we can only display but not edit
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existing contact details.
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\dots
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\snippet tutorials/addressbook/part2/addressbook.cpp setting readonly 1
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\dots
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\snippet tutorials/addressbook/part2/addressbook.cpp setting readonly 2
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Then, we instantiate our push buttons: \c addButton, \c submitButton, and
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\c cancelButton.
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\snippet tutorials/addressbook/part2/addressbook.cpp pushbutton declaration
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The \c addButton is displayed by invoking the \l{QPushButton::show()}
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{show()} function, while the \c submitButton and \c cancelButton are
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hidden by invoking \l{QPushButton::hide()}{hide()}. These two push
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buttons will only be displayed when the user clicks \uicontrol Add and this is
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handled by the \c addContact() function discussed below.
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\snippet tutorials/addressbook/part2/addressbook.cpp connecting signals and slots
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We connect the push buttons' \l{QPushButton::clicked()}{clicked()} signal
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to their respective slots. The figure below illustrates this.
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\image addressbook-tutorial-part2-signals-and-slots.png
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Next, we arrange our push buttons neatly to the right of our address book
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widget, using a QVBoxLayout to line them up vertically.
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\snippet tutorials/addressbook/part2/addressbook.cpp vertical layout
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The \l{QBoxLayout::addStretch()}{addStretch()} function is used to ensure
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the push buttons are not evenly spaced, but arranged closer to the top of
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the widget. The figure below shows the difference between using
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\l{QBoxLayout::addStretch()}{addStretch()} and not using it.
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\image addressbook-tutorial-part2-stretch-effects.png
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We then add \c buttonLayout1 to \c mainLayout, using
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\l{QGridLayout::addLayout()}{addLayout()}. This gives us nested layouts
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as \c buttonLayout1 is now a child of \c mainLayout.
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\snippet tutorials/addressbook/part2/addressbook.cpp grid layout
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Our layout coordinates now look like this:
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\image addressbook-tutorial-part2-labeled-layout.png
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In the \c addContact() function, we store the last displayed contact
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details in \c oldName and \c oldAddress. Then we clear these input
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fields and turn off the read-only mode. The focus is set on \c nameLine
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and we display \c submitButton and \c cancelButton.
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\snippet tutorials/addressbook/part2/addressbook.cpp addContact
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The \c submitContact() function can be divided into three parts:
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\list 1
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\li We extract the contact's details from \c nameLine and \c addressText
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and store them in QString objects. We also validate to make sure that the
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user did not click \uicontrol Submit with empty input fields; otherwise, a
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QMessageBox is displayed to remind the user for a name and address.
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\snippet tutorials/addressbook/part2/addressbook.cpp submitContact part1
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\li We then proceed to check if the contact already exists. If it does not
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exist, we add the contact to \c contacts and we display a QMessageBox to
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inform the user that the contact has been added.
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\snippet tutorials/addressbook/part2/addressbook.cpp submitContact part2
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If the contact already exists, again, we display a QMessageBox to inform
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the user about this, preventing the user from adding duplicate contacts.
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Our \c contacts object is based on key-value pairs of name and address,
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hence, we want to ensure that \e key is unique.
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\li Once we have handled both cases mentioned above, we restore the push
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buttons to their normal state with the following code:
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\snippet tutorials/addressbook/part2/addressbook.cpp submitContact part3
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\endlist
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The screenshot below shows the QMessageBox object we use to display
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information messages to the user.
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\image addressbook-tutorial-part2-add-successful.png
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The \c cancel() function restores the last displayed contact details and
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enables \c addButton, as well as hides \c submitButton and
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\c cancelButton.
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\snippet tutorials/addressbook/part2/addressbook.cpp cancel
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The general idea behind adding a contact is to give the user the
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flexibility to click \uicontrol Submit or \uicontrol Cancel at any time. The flowchart below
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further explains this concept:
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\image addressbook-tutorial-part2-add-flowchart.png
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*/
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/*!
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\example tutorials/addressbook/part3
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\title Part 3 - Navigating between Entries
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\brief Explains the code that enables navigating the contacts.
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The address book is now about half complete. We should add the
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capability to navigate the contacts, but first we must
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decide what sort of a data structure we need for containing these
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contacts.
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In the previous section, we used a QMap of key-value pairs with
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the contact's name as the \e key, and the contact's address as the
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\e value. This works well for our case. However, in order to
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navigate and display each entry, a little bit of enhancement is
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needed.
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We enhance the QMap by making it replicate a data structure similar to a
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circularly-linked list, where all elements are connected, including the
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first element and the last element. The figure below illustrates this data
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structure.
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\image addressbook-tutorial-part3-linkedlist.png
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\section1 Defining the AddressBook Class
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To add navigation functions to the address book, we must add two
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more slots to the \c AddressBook class: \c next() and \c
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previous() to the \c addressbook.h file:
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\snippet tutorials/addressbook/part3/addressbook.h navigation functions
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We also require another two QPushButton objects, so we declare \c nextButton
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and \c previousButton as private variables:
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\snippet tutorials/addressbook/part3/addressbook.h navigation pushbuttons
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\section1 Implementing the AddressBook Class
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In the \c AddressBook constructor in \c addressbook.cpp, we instantiate
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\c nextButton and \c previousButton and disable them by default. This is
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because navigation is only enabled when there is more than one contact
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in the address book.
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\snippet tutorials/addressbook/part3/addressbook.cpp navigation pushbuttons
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We then connect these push buttons to their respective slots:
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\snippet tutorials/addressbook/part3/addressbook.cpp connecting navigation signals
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The image below is the expected graphical user interface.
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\image addressbook-tutorial-part3-screenshot.png
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We follow basic conventions for \c next() and \c previous() functions by
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placing the \c nextButton on the right and the \c previousButton on the
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left. In order to achieve this intuitive layout, we use QHBoxLayout to
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place the widgets side-by-side:
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\snippet tutorials/addressbook/part3/addressbook.cpp navigation layout
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The QHBoxLayout object, \c buttonLayout2, is then added to \c mainLayout.
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\snippet tutorials/addressbook/part3/addressbook.cpp adding navigation layout
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The figure below shows the coordinates of the widgets in \c mainLayout.
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\image addressbook-tutorial-part3-labeled-layout.png
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Within our \c addContact() function, we have to disable these buttons so
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that the user does not attempt to navigate while adding a contact.
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\snippet tutorials/addressbook/part3/addressbook.cpp disabling navigation
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Also, in our \c submitContact() function, we enable the navigation
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buttons, \c nextButton and \c previousButton, depending on the size
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of \c contacts. As mentioned earlier, navigation is only enabled when
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there is more than one contact in the address book. The following lines
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of code demonstrates how to do this:
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\snippet tutorials/addressbook/part3/addressbook.cpp enabling navigation
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We also include these lines of code in the \c cancel() function.
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Recall that we intend to emulate a circularly-linked list with our QMap
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object, \c contacts. So, in the \c next() function, we obtain an iterator
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for \c contacts and then:
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\list
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\li If the iterator is not at the end of \c contacts, we increment it
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by one.
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\li If the iterator is at the end of \c contacts, we move it to the
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beginning of \c contacts. This gives us the illusion that our QMap is
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working like a circularly-linked list.
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\endlist
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\snippet tutorials/addressbook/part3/addressbook.cpp next() function
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Once we have iterated to the correct object in \c contacts, we display
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its contents on \c nameLine and \c addressText.
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Similarly, for the \c previous() function, we obtain an iterator for
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\c contacts and then:
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\list
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\li If the iterator is at the end of \c contacts, we clear the
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display and return.
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\li If the iterator is at the beginning of \c contacts, we move it to
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the end.
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\li We then decrement the iterator by one.
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\endlist
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\snippet tutorials/addressbook/part3/addressbook.cpp previous() function
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Again, we display the contents of the current object in \c contacts.
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*/
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/*!
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\example tutorials/addressbook/part4
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\title Part 4 - Editing and Removing Addresses
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\brief Explains how to add edit and remove functionality.
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Now we look at ways to modify the contents of contacts stored in
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the address book.
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\image addressbook-tutorial-screenshot.png
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|
|
|
We now have an address book that not only holds contacts in an
|
|
organized manner, but also allows navigation. It would be
|
|
convenient to include edit and remove functions so that a
|
|
contact's details can be changed when needed. However, this
|
|
requires a little improvement, in the form of enums. We defined
|
|
two modes: \c{AddingMode} and \c{NavigationMode}, but they were
|
|
not defined as enum values. Instead, we enabled and disabled the
|
|
corresponding buttons manually, resulting in multiple lines of
|
|
repeated code.
|
|
|
|
Here we define the \c Mode enum with three different values:
|
|
|
|
\list
|
|
\li \c{NavigationMode},
|
|
\li \c{AddingMode}, and
|
|
\li \c{EditingMode}.
|
|
\endlist
|
|
|
|
\section1 Defining the AddressBook Class
|
|
|
|
The \c addressbook.h file is updated to contain the \c Mode enum:
|
|
|
|
\snippet tutorials/addressbook/part4/addressbook.h Mode enum
|
|
|
|
We also add two new slots, \c editContact() and \c removeContact(), to
|
|
our current list of public slots.
|
|
|
|
\snippet tutorials/addressbook/part4/addressbook.h edit and remove slots
|
|
|
|
In order to switch between modes, we introduce the \c updateInterface() function
|
|
to control the enabling and disabling of all QPushButton objects. We also
|
|
add two new push buttons, \c editButton and \c removeButton, for the edit
|
|
and remove functions mentioned earlier.
|
|
|
|
\snippet tutorials/addressbook/part4/addressbook.h updateInterface() declaration
|
|
\dots
|
|
\snippet tutorials/addressbook/part4/addressbook.h buttons declaration
|
|
\dots
|
|
\snippet tutorials/addressbook/part4/addressbook.h mode declaration
|
|
|
|
Lastly, we declare \c currentMode to keep track of the enum's current mode.
|
|
|
|
\section1 Implementing the AddressBook Class
|
|
|
|
We now implement the mode-changing features of the address
|
|
book. The \c editButton and \c removeButton are instantiated and
|
|
disabled by default. The address book starts with zero contacts
|
|
in memory.
|
|
|
|
\snippet tutorials/addressbook/part4/addressbook.cpp edit and remove buttons
|
|
|
|
These buttons are then connected to their respective slots, \c editContact()
|
|
and \c removeContact(), and we add them to \c buttonLayout1.
|
|
|
|
\snippet tutorials/addressbook/part4/addressbook.cpp connecting edit and remove
|
|
\dots
|
|
\snippet tutorials/addressbook/part4/addressbook.cpp adding edit and remove to the layout
|
|
|
|
The \c editContact() function stores the contact's old details in
|
|
\c oldName and \c oldAddress, before switching the mode to \c EditingMode.
|
|
In this mode, the \c submitButton and \c cancelButton are both enabled,
|
|
hence, the user can change the contact's details and click either button.
|
|
|
|
\snippet tutorials/addressbook/part4/addressbook.cpp editContact() function
|
|
|
|
The \c submitContact() function has been divided in two with an \c{if-else}
|
|
statement. We check \c currentMode to see if it's in \c AddingMode. If it is,
|
|
we proceed with our adding process.
|
|
|
|
\snippet tutorials/addressbook/part4/addressbook.cpp submitContact() function beginning
|
|
\dots
|
|
\snippet tutorials/addressbook/part4/addressbook.cpp submitContact() function part1
|
|
|
|
Otherwise, we check to see if \c currentMode is in \c EditingMode. If it
|
|
is, we compare \c oldName with \c name. If the name has changed, we remove
|
|
the old contact from \c contacts and insert the newly updated contact.
|
|
|
|
\snippet tutorials/addressbook/part4/addressbook.cpp submitContact() function part2
|
|
|
|
If only the address has changed (i.e., \c oldAddress is not the same as \c address),
|
|
we update the contact's address. Lastly, we set \c currentMode to
|
|
\c NavigationMode. This is an important step as it re-enables all the
|
|
disabled push buttons.
|
|
|
|
To remove a contact from the address book, we implement the
|
|
\c removeContact() function. This function checks to see if the contact
|
|
exists in \c contacts.
|
|
|
|
\snippet tutorials/addressbook/part4/addressbook.cpp removeContact() function
|
|
|
|
If it does, we display a QMessageBox, to confirm the removal with the
|
|
user. Once the user has confirmed, we call \c previous() to ensure that the
|
|
user interface shows another contact, and we remove the contact using \l{QMap}'s
|
|
\l{QMap::remove()}{remove()} function. As a courtesy, we display a QMessageBox
|
|
to inform the user. Both the message boxes used in this function are shown below:
|
|
|
|
\image addressbook-tutorial-part4-remove.png
|
|
|
|
\section2 Updating the User Interface
|
|
|
|
We mentioned the \c updateInterface() function earlier as a means to
|
|
enable and disable the push buttons depending on the current mode.
|
|
The function updates the current mode according to the \c mode argument
|
|
passed to it, assigning it to \c currentMode before checking its value.
|
|
|
|
Each of the push buttons is then enabled or disabled, depending on the
|
|
current mode. The code for \c AddingMode and \c EditingMode is shown below:
|
|
|
|
\snippet tutorials/addressbook/part4/addressbook.cpp update interface() part 1
|
|
|
|
For \c NavigationMode, however, we include conditions within the parameters
|
|
of the QPushButton::setEnabled() function. This is to ensure that
|
|
\c editButton and \c removeButton are enabled when there is at least one
|
|
contact in the address book; \c nextButton and \c previousButton are only
|
|
enabled when there is more than one contact in the address book.
|
|
|
|
\snippet tutorials/addressbook/part4/addressbook.cpp update interface() part 2
|
|
|
|
By setting the mode and updating the user interface in the same
|
|
function, we avoid the possibility of the user interface getting
|
|
out of sync with the internal state of the application.
|
|
*/
|
|
|
|
/*!
|
|
\example tutorials/addressbook/part5
|
|
\title Part 5 - Adding a Find Function
|
|
\brief Describes how to add a find function.
|
|
|
|
Here we look at ways to locate contacts and addresses in the
|
|
address book.
|
|
|
|
\image addressbook-tutorial-part5-screenshot.png
|
|
|
|
As we add contacts to our address book, it becomes tedious to
|
|
navigate the list with the \e Next and \e Previous buttons. A \e
|
|
Find function would be more efficient. The screenshot above shows
|
|
the \e Find button and its position on the panel of buttons.
|
|
|
|
When the user clicks on the \e Find button, it is useful to
|
|
display a dialog that prompts for a contact's name. Qt provides
|
|
QDialog, which we subclass here to implement a \c FindDialog
|
|
class.
|
|
|
|
\section1 Defining the FindDialog Class
|
|
|
|
\image addressbook-tutorial-part5-finddialog.png
|
|
|
|
In order to subclass QDialog, we first include the header for QDialog in
|
|
the \c finddialog.h file. Also, we use forward declaration to declare
|
|
QLineEdit and QPushButton since we will be using those widgets in our
|
|
dialog class.
|
|
|
|
As in our \c AddressBook class, the \c FindDialog class includes
|
|
the Q_OBJECT macro and its constructor is defined to accept a parent
|
|
QWidget, even though the dialog will be opened as a separate window.
|
|
|
|
\snippet tutorials/addressbook/part5/finddialog.h FindDialog header
|
|
|
|
We define a public function, \c getFindText(), to be used by classes that
|
|
instantiate \c FindDialog. This function allows these classes to obtain the
|
|
search string entered by the user. A public slot, \c findClicked(), is also
|
|
defined to handle the search string when the user clicks the \uicontrol Find
|
|
button.
|
|
|
|
Lastly, we define the private variables, \c findButton, \c lineEdit
|
|
and \c findText, corresponding to the \uicontrol Find button, the line edit
|
|
into which the user types the search string, and an internal string
|
|
used to store the search string for later use.
|
|
|
|
\section1 Implementing the FindDialog Class
|
|
|
|
Within the constructor of \c FindDialog, we set up the private variables,
|
|
\c lineEdit, \c findButton and \c findText. We use a QHBoxLayout to
|
|
position the widgets.
|
|
|
|
\snippet tutorials/addressbook/part5/finddialog.cpp constructor
|
|
|
|
We set the layout and window title, as well as connect the signals to their
|
|
respective slots. Notice that \c{findButton}'s \l{QPushButton::clicked()}
|
|
{clicked()} signal is connected to \c findClicked() and
|
|
\l{QDialog::accept()}{accept()}. The \l{QDialog::accept()}{accept()} slot
|
|
provided by QDialog hides the dialog and sets the result code to
|
|
\l{QDialog::}{Accepted}. We use this function to help \c{AddressBook}'s
|
|
\c findContact() function know when the \c FindDialog object has been
|
|
closed. We will explain this logic in further detail when discussing the
|
|
\c findContact() function.
|
|
|
|
\image addressbook-tutorial-part5-signals-and-slots.png
|
|
|
|
In \c findClicked(), we validate \c lineEdit to ensure that the user
|
|
did not click the \uicontrol Find button without entering a contact's name. Then, we set
|
|
\c findText to the search string, extracted from \c lineEdit. After that,
|
|
we clear the contents of \c lineEdit and hide the dialog.
|
|
|
|
\snippet tutorials/addressbook/part5/finddialog.cpp findClicked() function
|
|
|
|
The \c findText variable has a public getter function, \c getFindText(),
|
|
associated with it. Since we only ever set \c findText directly in both the
|
|
constructor and in the \c findClicked() function, we do not create a
|
|
setter function to accompany \c getFindText().
|
|
Because \c getFindText() is public, classes instantiating and using
|
|
\c FindDialog can always access the search string that the user has
|
|
entered and accepted.
|
|
|
|
\snippet tutorials/addressbook/part5/finddialog.cpp getFindText() function
|
|
|
|
\section1 Defining the AddressBook Class
|
|
|
|
To ensure we can use \c FindDialog from within our \c AddressBook class, we
|
|
include \c finddialog.h in the \c addressbook.h file.
|
|
|
|
\snippet tutorials/addressbook/part5/addressbook.h include finddialog's header
|
|
|
|
So far, all our address book features have a QPushButton and a
|
|
corresponding slot. Similarly, for the \uicontrol Find feature we have
|
|
\c findButton and \c findContact().
|
|
|
|
The \c findButton is declared as a private variable and the
|
|
\c findContact() function is declared as a public slot.
|
|
|
|
\snippet tutorials/addressbook/part5/addressbook.h findContact() declaration
|
|
\dots
|
|
\snippet tutorials/addressbook/part5/addressbook.h findButton declaration
|
|
|
|
Lastly, we declare the private variable, \c dialog, which we will use to
|
|
refer to an instance of \c FindDialog.
|
|
|
|
\snippet tutorials/addressbook/part5/addressbook.h FindDialog declaration
|
|
|
|
Once we have instantiated a dialog, we will want to use it more than once;
|
|
using a private variable allows us to refer to it from more than one place
|
|
in the class.
|
|
|
|
\section1 Implementing the AddressBook Class
|
|
|
|
Within the \c AddressBook class's constructor, we instantiate our private
|
|
objects, \c findButton and \c findDialog:
|
|
|
|
\snippet tutorials/addressbook/part5/addressbook.cpp instantiating findButton
|
|
\dots
|
|
\snippet tutorials/addressbook/part5/addressbook.cpp instantiating FindDialog
|
|
|
|
Next, we connect the \c{findButton}'s
|
|
\l{QPushButton::clicked()}{clicked()} signal to \c findContact().
|
|
|
|
\snippet tutorials/addressbook/part5/addressbook.cpp signals and slots for find
|
|
|
|
Now all that is left is the code for our \c findContact() function:
|
|
|
|
\snippet tutorials/addressbook/part5/addressbook.cpp findContact() function
|
|
|
|
We start out by displaying the \c FindDialog instance, \c dialog. This is
|
|
when the user enters a contact name to look up. Once the user clicks
|
|
the dialog's \c findButton, the dialog is hidden and the result code is
|
|
set to QDialog::Accepted. This ensures that
|
|
our \c if statement is always true.
|
|
|
|
We then proceed to extract the search string, which in this case is
|
|
\c contactName, using \c{FindDialog}'s \c getFindText() function. If the
|
|
contact exists in our address book, we display it immediately. Otherwise,
|
|
we display the QMessageBox shown below to indicate that their search
|
|
failed.
|
|
|
|
\image addressbook-tutorial-part5-notfound.png
|
|
*/
|
|
|
|
/*!
|
|
\example tutorials/addressbook/part6
|
|
\title Part 6 - Loading and Saving
|
|
\brief Describes how to add save and load functionality.
|
|
|
|
This part covers the Qt file handling features we use to write
|
|
loading and saving routines for the address book.
|
|
|
|
\image addressbook-tutorial-part6-screenshot.png
|
|
|
|
Although browsing and searching the contact list are useful
|
|
features, our address book is not complete until we can save
|
|
existing contacts and load them again at a later time.
|
|
|
|
Qt provides a number of classes for \l{Input/Output and Networking}
|
|
{input and output}, but we have chosen to use two which are simple to use
|
|
in combination: QFile and QDataStream.
|
|
|
|
A QFile object represents a file on disk that can be read from and written
|
|
to. QFile is a subclass of the more general QIODevice class which
|
|
represents many different kinds of devices.
|
|
|
|
A QDataStream object is used to serialize binary data so that it can be
|
|
stored in a QIODevice and retrieved again later. Reading from a QIODevice
|
|
and writing to it is as simple as opening the stream - with the respective
|
|
device as a parameter - and reading from or writing to it.
|
|
|
|
|
|
\section1 Defining the AddressBook Class
|
|
|
|
We declare two public slots, \c saveToFile() and \c loadFromFile(), as well
|
|
as two QPushButton objects, \c loadButton and \c saveButton.
|
|
|
|
\snippet tutorials/addressbook/part6/addressbook.h save and load functions declaration
|
|
\dots
|
|
\snippet tutorials/addressbook/part6/addressbook.h save and load buttons declaration
|
|
|
|
\section1 Implementing the AddressBook Class
|
|
|
|
In our constructor, we instantiate \c loadButton and \c saveButton.
|
|
Ideally, it would be more user-friendly to set the push buttons' labels
|
|
to "Load contacts from a file" and "Save contacts to a file". However, due
|
|
to the size of our other push buttons, we set the labels to \uicontrol{Load...}
|
|
and \uicontrol{Save...}. Fortunately, Qt provides a simple way to set tooltips with
|
|
\l{QWidget::setToolTip()}{setToolTip()} and we use it in the following way
|
|
for our push buttons:
|
|
|
|
\snippet tutorials/addressbook/part6/addressbook.cpp tooltip 1
|
|
\dots
|
|
\snippet tutorials/addressbook/part6/addressbook.cpp tooltip 2
|
|
|
|
Although it is not shown here, just like the other features we implemented,
|
|
we add the push buttons to the layout panel on the right, \c buttonLayout1,
|
|
and we connect the push buttons' \l{QPushButton::clicked()}{clicked()}
|
|
signals to their respective slots.
|
|
|
|
For the saving feature, we first obtain \c fileName using
|
|
QFileDialog::getSaveFileName(). This is a convenience function provided
|
|
by QFileDialog, which pops up a modal file dialog and allows the user to
|
|
enter a file name or select any existing \c{.abk} file. The \c{.abk} file
|
|
is our Address Book extension that we create when we save contacts.
|
|
|
|
\snippet tutorials/addressbook/part6/addressbook.cpp saveToFile() function part1
|
|
|
|
The file dialog that pops up is displayed in the screenshot below:
|
|
|
|
\image addressbook-tutorial-part6-save.png
|
|
|
|
If \c fileName is not empty, we create a QFile object, \c file, with
|
|
\c fileName. QFile works with QDataStream as QFile is a QIODevice.
|
|
|
|
Next, we attempt to open the file in \l{QIODeviceBase::}{WriteOnly} mode.
|
|
If this is unsuccessful, we display a QMessageBox to inform the user.
|
|
|
|
\snippet tutorials/addressbook/part6/addressbook.cpp saveToFile() function part2
|
|
|
|
Otherwise, we instantiate a QDataStream object, \c out, to write the open
|
|
file. QDataStream requires that the same version of the stream is used
|
|
for reading and writing. We ensure that this is the case by setting the
|
|
version used to the \l{QDataStream::Qt_4_5}{version introduced with Qt 4.5}
|
|
before serializing the data to \c file.
|
|
|
|
\snippet tutorials/addressbook/part6/addressbook.cpp saveToFile() function part3
|
|
|
|
For the loading feature, we also obtain \c fileName using
|
|
QFileDialog::getOpenFileName(). This function, the counterpart to
|
|
QFileDialog::getSaveFileName(), also pops up the modal file dialog and
|
|
allows the user to enter a file name or select any existing \c{.abk} file
|
|
to load it into the address book.
|
|
|
|
\snippet tutorials/addressbook/part6/addressbook.cpp loadFromFile() function part1
|
|
|
|
On Windows, for example, this function pops up a native file dialog, as
|
|
shown in the following screenshot.
|
|
|
|
\image addressbook-tutorial-part6-load.png
|
|
|
|
If \c fileName is not empty, again, we use a QFile object, \c file, and
|
|
attempt to open it in \l{QIODeviceBase::}{ReadOnly} mode. Similar to our
|
|
implementation of \c saveToFile(), if this attempt is unsuccessful, we
|
|
display a QMessageBox to inform the user.
|
|
|
|
\snippet tutorials/addressbook/part6/addressbook.cpp loadFromFile() function part2
|
|
|
|
Otherwise, we instantiate a QDataStream object, \c in, set its version as
|
|
above and read the serialized data into the \c contacts data structure.
|
|
The \c contacts object is emptied before data is read into it to simplify
|
|
the file reading process. A more advanced method would be to read the
|
|
contacts into a temporary QMap object, and copy over non-duplicate contacts
|
|
into \c contacts.
|
|
|
|
\snippet tutorials/addressbook/part6/addressbook.cpp loadFromFile() function part3
|
|
|
|
To display the contacts that have been read from the file, we must first
|
|
validate the data obtained to ensure that the file we read from actually
|
|
contains address book contacts. If it does, we display the first contact;
|
|
otherwise, we display a QMessageBox to inform the user about the problem.
|
|
Lastly, we update the interface to enable and disable the push buttons
|
|
accordingly.
|
|
*/
|
|
|
|
/*!
|
|
\example tutorials/addressbook/part7
|
|
\title Part 7 - Additional Features
|
|
\brief Describes how to export data in VCard format.
|
|
|
|
This part covers some additional features that make the address
|
|
book more convenient for the frequent user.
|
|
|
|
\image addressbook-tutorial-part7-screenshot.png
|
|
|
|
Although our address book is useful in isolation, it would be
|
|
better if we could exchange contact data with other applications.
|
|
The vCard format is a popular file format that can be used for
|
|
this purpose. Here we extend our address book client to allow
|
|
contacts to be exported to vCard \c{.vcf} files.
|
|
|
|
\section1 Defining the AddressBook Class
|
|
|
|
We add a QPushButton object, \c exportButton, and a corresponding public
|
|
slot, \c exportAsVCard() to our \c AddressBook class in the
|
|
\c addressbook.h file.
|
|
|
|
\snippet tutorials/addressbook/part7/addressbook.h exportAsVCard() declaration
|
|
\dots
|
|
\snippet tutorials/addressbook/part7/addressbook.h exportButton declaration
|
|
|
|
\section1 Implementing the AddressBook Class
|
|
|
|
Within the \c AddressBook constructor, we connect \c{exportButton}'s
|
|
\l{QPushButton::clicked()}{clicked()} signal to \c exportAsVCard().
|
|
We also add this button to our \c buttonLayout1, the layout responsible
|
|
for our panel of buttons on the right.
|
|
|
|
In our \c exportAsVCard() function, we start by extracting the contact's
|
|
name into \c name. We declare \c firstName, \c lastName and \c nameList.
|
|
Next, we look for the index of the first white space in \c name. If there
|
|
is a white space, we split the contact's name into \c firstName and
|
|
\c lastName. Then, we replace the space with an underscore ("_").
|
|
Alternately, if there is no white space, we assume that the contact only
|
|
has a first name.
|
|
|
|
\snippet tutorials/addressbook/part7/addressbook.cpp export function part1
|
|
|
|
As with the \c saveToFile() function, we open a file dialog to let the user
|
|
choose a location for the file. Using the file name chosen, we create an
|
|
instance of QFile to write to.
|
|
|
|
We attempt to open the file in \l{QIODeviceBase::}{WriteOnly} mode. If this
|
|
process fails, we display a QMessageBox to inform the user about the
|
|
problem and return. Otherwise, we pass the file as a parameter to a
|
|
QTextStream object, \c out. Like QDataStream, the QTextStream class
|
|
provides functionality to read and write plain text to files. As a result,
|
|
the \c{.vcf} file generated can be opened for editing in a text editor.
|
|
|
|
\snippet tutorials/addressbook/part7/addressbook.cpp export function part2
|
|
|
|
We then write out a vCard file with the \c{BEGIN:VCARD} tag, followed by
|
|
the \c{VERSION:2.1} tag. The contact's name is written with the \c{N:}
|
|
tag. For the \c{FN:} tag, which fills in the "File as" property of a vCard,
|
|
we have to check whether the contact has a last name or not. If the contact
|
|
does, we use the details in \c nameList to fill it. Otherwise, we write
|
|
\c firstName only.
|
|
|
|
\snippet tutorials/addressbook/part7/addressbook.cpp export function part3
|
|
|
|
We proceed to write the contact's address. The semicolons in the address
|
|
are escaped with "\\", the newlines are replaced with semicolons, and the
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commas are replaced with spaces. Lastly, we write the \c{ADR;HOME:;}
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tag, followed by \c address and then the \c{END:VCARD} tag.
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\snippet tutorials/addressbook/part7/addressbook.cpp export function part4
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In the end, a QMessageBox is displayed to inform the user that the vCard
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|
has been successfully exported.
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\e{vCard is a trademark of the \l{http://www.imc.org}
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|
{Internet Mail Consortium}}.
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*/
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