C++ Qt4 GUI编程实战指南

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"C++ GUI Programming with Qt 4, 2nd Edition 是一本由 Jasmin Blanchette 和 Mark Summerfield 编著的书籍，由 Prentice Hall 出版社于2008年2月4日发行。这本书是针对Qt 4.3编程的官方最佳实践指南，适用于初学者。Qt是一个强大的C++库，允许开发者创建可以在Windows、Linux/Unix、Mac OS X以及嵌入式Linux上原生运行的应用程序，无需更改源代码。本书涵盖了Qt 4.3的最新功能和改进，如增强的图形支持，并提供了从模型/视图架构实现到数据库访问、XML集成和子类化的高级技术解决方案。" 在《C++ GUI Programming with Qt 4》第二版中，作者深入浅出地介绍了Qt开发的关键概念和技术，旨在帮助读者快速掌握Qt框架。书中的例子实用且具有代表性，确保读者能够通过实践理解理论知识。以下是本书可能涵盖的一些核心知识点： 1. **Qt框架基础**：了解Qt的核心组件，如QCoreApplication、QObject及其派生类，理解事件驱动的编程模型。 2. **窗口和控件**：学习如何创建和使用Qt的各种窗口部件（widgets），如QPushButton、QLineEdit、QLabel等，以及如何自定义控件以满足特定需求。 3. **信号与槽机制**：理解Qt的信号与槽机制，这是其异步通信的核心，用于对象间的通信。 4. **模型/视图架构**：学习如何实现数据和界面的分离，使用QModel、QView和QDelegate来处理复杂的数据显示和编辑。 5. **布局管理**：掌握如何使用QLayout来自动调整窗口部件的大小和位置，以适应不同分辨率的屏幕。 6. **图形视图框架**：探索Qt 4.3中增强的图形支持，如QGraphicsView和QGraphicsScene，用于创建富交互性的2D图形用户界面。 7. **数据库集成**：学习如何使用QSqlDatabase、QSqlQuery等类进行数据库操作，实现数据存储和检索。 8. **网络编程**：了解Qt的网络模块，如QNetworkAccessManager和QNetworkReply，用于处理HTTP请求和响应。 9. **XML处理**：学习使用QDomDocument和QXmlStreamReader/QXmlStreamWriter解析和生成XML文档。 10. **国际化与本地化**：掌握如何使用Qt的翻译系统（QTranslator）和资源管理（QResource）实现多语言支持和资源管理。 11. **线程编程**：理解Qt的多线程支持，包括QThread和信号槽在多线程环境中的使用。 12. **测试与调试**：学习如何使用Qt的测试框架（QtTest）编写单元测试，以及利用Qt Creator进行调试。通过本书，读者不仅可以了解到Qt的基本用法，还能深入到高级特性，从而能够开发出高效、稳定、跨平台的C++应用程序。作为初学者，这本书提供了一个良好的起点，引导读者逐步成为熟练的Qt开发者。

It is now possible to try the program on your own machine. It should look like the one shown in Figure 1.1. First, you will need to

install Qt 4.3.2 (or a later Qt 4 release), a process that is explained in Appendix A. From now on, we will assume that you have a

correctly installed copy of Qt 4 and that Qt's bin directory is in your PATH environment variable. (On Windows, this is done

automatically by the Qt installation program.) You will also need the program's code in a file called hello.cpp in a directory

called hello. You can type in hello.cpp yourself or copy it from the examples that accompany this book, where it is

available as examples/chap01/hello/hello.cpp. (All the examples are available from the book's web site,

http://www.informit.com/title/0132354160.)

Figure 1.1. Hello on Linux

From a command prompt, change the directory to hello, and type

qmake -project

to create a platform-independent project file (hello.pro), and then type

qmake hello.pro

to create a platform-specific makefile from the project file. (The qmake tool is covered in more detail in Appendix B.) Type

make to build the program. Run it by typing hello on Windows, ./hello on Unix, and open hello.app on Mac OS X.

To terminate the program, click the close button in the window's title bar.

If you are using Windows and have installed the Qt Open Source Edition and the MinGW compiler, you will have a shortcut to an

MS-DOS Prompt window that has all the environment variables correctly set up for Qt. If you start this window, you can compile

Qt applications within it using qmake and make as described previously. The executables produced are put in the application's

debug or release folder (e.g., C:\examples\chap01\hello\release\hello.exe).

If you are using Microsoft Visual C++ with a commercial version of Qt, you will need to run nmake instead of make.

Alternatively, you can create a Visual Studio project file from hello.pro by typing

qmake -tp vc hello.pro

and then build the program in Visual Studio. If you are using Xcode on Mac OS X, you can generate an Xcode project using the

command

qmake -spec macx-xcode hello.pro

Before we go on to the next example, let's have some fun: Replace the line

QLabel *label = new QLabel("Hello Qt!");

with

QLabel *label = new QLabel("<h2><i>Hello</i> "

"<font color=red>Qt!</font></h2>");

and rebuild the application. When run, it should look like Figure 1.2. As the example illustrates, it's easy to brighten up a Qt

application's user interface using some simple HTML-style formatting.

Figure 1.2. A label with basic HTML formatting

Part I: Basic Qt

1. Getting Started

Hello Qt•

Making Connections•

Laying Out Widgets•

Using the Reference Documentation•

This chapter shows how to combine basic C++ with the functionality provided by Qt to create a few small graphical user interface

(GUI) applications. This chapter also introduces two key Qt ideas: "signals and slots" and layouts. In Chapter 2, we will go into

more depth, and in Chapter 3, we will start building a more realistic application.

If you already know Java or C# but have limited experience with C++, you might want to start by reading the C++ introduction in

Appendix D.

Hello Qt

Let's start with a very simple Qt program. We will first study it line by line, and then see how to compile and run it.

1 #include <QApplication>

2 #include <QLabel>

3 int main(int argc, char *argv[])

4 {

5 QApplication app(argc, argv);

6 QLabel *label = new QLabel("Hello Qt!");

7 label->show();

8 return app.exec();

9 }

Lines 1 and 2 include the definitions of the QApplication and QLabel classes. For every Qt class, there is a header file with

the same name (and capitalization) as the class that contains the class's definition.

Line 5 creates a QApplication object to manage application-wide resources. The QApplication constructor requires argc

and argv because Qt supports a few command-line arguments of its own.

Line 6 creates a QLabel widget that displays "Hello Qt!". In Qt and Unix terminology, a widget is a visual element in a user

interface. The term stems from "window gadget" and is the equivalent of both "control" and "container" in Windows terminology.

Buttons, menus, scroll bars, and frames are all examples of widgets. Widgets can contain other widgets; for example, an

application window is usually a widget that contains a QMenuBar, a few QToolBars, a QStatusBar, and some other widgets.

Most applications use a QMainWindow or a QDialog as the application window, but Qt is so flexible that any widget can be a

window. In this example, the QLabel widget is the application window.

Line 7 makes the label visible. Widgets are always created hidden so that we can customize them before showing them, thereby

avoiding flicker.

Line 8 passes control of the application on to Qt. At this point, the program enters the event loop. This is a kind of stand-by mode

where the program waits for user actions such as mouse clicks and key presses. User actions generate events (also called

"messages") to which the program can respond, usually by executing one or more functions. For example, when the user clicks a

widget, a "mouse press" and a "mouse release" event are generated. In this respect, GUI applications differ drastically from

conventional batch programs, which typically process input, produce results, and terminate without human intervention.

For simplicity, we don't bother calling delete on the QLabel object at the end of the main() function. This memory leak is

harmless in such a small program, since the memory will be reclaimed by the operating system when the program terminates.