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This tutorial gives an introduction to GUI programming using the Qt SDK. ### Screenshot In the process, we will learn about some basic technologies provided by Qt, such as: \list \o Widgets and layout managers \o Container classes \o Signals and slots \o Input and output devices \endlist If you are completely new to Qt, please read \l{How to Learn Qt} if you have not already done so. The tutorial's source code is located in Qt's \c{examples/tutorials/addressbook} directory. Tutorial chapters: \list 1 \o \l{Designing the User Interface} \o \l{Adding Addresses} \o \l{Navigating between Entries} \o \l{Editing and Removing Addresses} \o \l{Adding a Find Function} \o \l{Loading and Saving} \o \l{Additional Features} \endlist Although this little application does not look much like a fully-fledged modern GUI application, it uses many of the basic techniques that are used in more complex applications. After you have worked through it, we recommend checking out the \l{mainwindows/application}{Application} example, which presents a small GUI application, with menus, toolbars, a status bar, and so on. */ /*! \page tutorials-addressbook-sdk-part1.html \contentspage {Address Book Tutorial}{Contents} \nextpage \l{Adding Addresses}{Chapter 2} \title Address Book 1 - Designing the User Interface The first part of this tutorial covers the design of the basic graphical user interface (GUI) we use for the Address Book application. The first step to creating a GUI program is to design the user interface. In this chapter, our goal is to set up the labels and input fields needed to implement a basic address book application. The figure below is a screenshot of our expected output. \image addressbook-tutorial-part1-screenshot.png We begin by launching Qt Creator and use it to generate a new project. To do this, select \gui New from the \gui File menu. In the \gui{New File or Project} dialog. Follow the step by step guide on how to create a \gui Project with Qt Creator, refer to the document \l{Creating a Project in Qt Creator}{here}. Ensure that you select QWidget as your subclass and name it \c AddressBook. There are five files generated in this \gui{Project}: \list \o \c{addressbook.pro} - the project file, \o \c{addressbook.h} - the definition file for the \c AddressBook class, \o \c{addressbook.cpp} - the implementation file for the \c AddressBook class, \o \c{main.cpp} - the file containing a \c main() function, with an instance of \c AddressBook, and \o \c{addressbook.ui} - the user interface file created with \QD. \endlist Now we have all the files we need, let's move on to designing the user interface. \section1 Placing the Widgets on the Form In the \gui{Project Sidebar}, double-click on the \c{addressbook.ui} file. The \QD plugin will be launched, allowing you to design your program's user interface. We require two \l{QLabel}s to label the input fields as well as a QLineEdit and a QTextEdit as the input fields. So, drag those widgets from the \gui{Widget Box} to your form. In the \gui{Property Editor}, set their \gui{objectName} property to \c nameLabel and \c addressLabel for the \l{QLabel}s, \c nameLine for the QLineEdit and finally, \c addressText for the QTextEdit. Next, we have to position the widgets properly, according to the screenshot earlier. We use a QGridLayout to position our labels and input fields in a structured manner. QGridLayout divides the available space into a grid and places widgets in the cells we specify with row and column numbers. The diagram below shows the layout cells and the position of our widgets. \image addressbook-tutorial-part1-labeled-screenshot.png \section1 Qt Programming - Subclassing When writing Qt programs, we usually subclass Qt objects to add functionality. This is one of the essential concepts behind creating custom widgets or collections of standard widgets. Subclassing to extend or change the behavior of a widget has the following advantages: \list \o We can write implementations of virtual or pure virtual functions to obtain exactly what we need, falling back on the base class's implementation when necessary. \o It allows us to encapsulate parts of the user interface within a class, so that the other parts of the application do not need to know about the individual widgets in the user interface. \o The subclass can be used to create multiple custom widgets in the same application or library, and the code for the subclass can be reused in other projects. \endlist */