使用Qt4进行C++ GUI编程实战

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"C++ GUI编程与Qt4是关于使用Qt框架进行C++图形用户界面开发的专业书籍，由Jasmin Blanchette和Mark Summerfield撰写。本书由Prentice Hall出版社于2006年6月出版，适用于Windows、Linux/Unix、Mac OS X和嵌入式Linux平台，无需修改源代码即可实现跨平台运行。它专注于Qt4.1版本，这是Qt历史上功能最强大的版本之一。全书深入讲解了Qt4编程的最佳实践，涵盖了从Qt的模型/视图架构到新的2D绘图引擎等一系列关键技术和策略。作者，作为Trolltech（Qt的创建公司）的内部专家，提供了对Qt事件模型和布局系统的独特见解。此外，书中通过实际示例介绍了从基础GUI开发到高级数据库和XML集成的优化技巧。特别地，书中新增章节详细探讨了Qt4的模型/视图架构，这是一个强大且灵活的设计模式，允许开发者分离数据和显示逻辑，提高了代码的可复用性和可维护性。另一个重点是Qt的新插件系统，它增强了应用程序的扩展性和模块化，使得开发者可以轻松添加新功能或替换现有组件。本书还涵盖了以下主题： 1. **Qt基础**：介绍Qt库的基本概念和使用方法，包括窗口和控件的创建，事件处理，以及信号和槽机制。 2. **模型/视图编程**：深入探讨如何使用模型/视图架构来处理数据展示，包括列表视图、树视图和表格视图。 3. **2D绘图**：讲解如何利用Qt的绘图API创建自定义图形，以及动画和图形效果。 4. **布局管理**：介绍如何有效地组织和调整窗口小部件的位置和大小，以适应不同屏幕尺寸和分辨率。 5. **数据库集成**：涵盖使用Qt的SQL模块连接和操作各种类型的数据库。 6. **XML支持**：解释如何读写XML文件，以及在应用程序中使用XML数据。 7. **网络编程**：讲解如何使用Qt进行网络通信，如HTTP请求、套接字编程等。 8. **国际化和本地化**：指导如何使应用程序支持多语言环境。 9. **性能优化**：提供最佳实践，帮助开发者优化Qt应用的性能。通过阅读此书，读者将全面掌握Qt4的高级特性，能够构建高效、稳定且易于维护的C++ GUI应用。" 这份资源是C++程序员和Qt初学者的理想教程，它不仅提供了理论知识，还包含丰富的实践案例，帮助读者将所学应用于实际项目中。对于希望提升Qt开发技能或初次接触Qt的开发者来说，这本书无疑是一本权威且实用的参考书。

instance, QPushButton emits a clicked() signal when the user clicks the button. A signal can be

connected to a function (called a slot in that context), so that when the signal is emitted, the slot is

automatically executed. In our example, we connect the button's clicked() signal to the

QApplication object's quit() slot. The SIGNAL() and SLOT() macros are part of the syntax; they are

explained in more detail in the next chapter.

[*]

Qt signals are unrelated to Unix signals. In this book, we are only concerned with Qt signals.

Figure 1.3. The Quit application

We will now build the application. We assume that you have created a directory called quit

containing quit.cpp. Run qmake in the quit directory to generate the project file, then run it again to

generate a makefile, as follows:

qmake -project

qmake quit.pro

Now build the application, and run it. If you click Quit, or press Space (which presses the button),

the application will terminate.

Laying Out Widgets

In this section, we will create a small example application that demonstrates how to use layouts to

manage the geometry of widgets in a window and how to use signals and slots to synchronize two

widgets. The application asks for the user's age, which the user can enter by manipulating either a

spin box or a slider.

The application consists of three widgets: a QSpinBox, a QSlider, and a QWidget. The QWidget is the

application's main window. The QSpinBox and the QSlider are rendered inside the QWidget; they are

children of the QWidget. Alternatively, we can say that the QWidget is the parent of the QSpinBox

and the QSlider. The QWidget has no parent itself because it is being used as a top-level window.

The constructors for QWidget and all of its subclasses take a QWidget * parameter that specifies the

parent widget.

Figure 1.4. The Age application

Here's the source code:

1 #include <QApplication>

2 #include <QHBoxLayout>

3 #include <QSlider>

4 #include <QSpinBox>

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

6 {

7 QApplication app(argc, argv);

8 QWidget *window = new QWidget;

9 window->setWindowTitle("Enter Your Age");

10 QSpinBox *spinBox = new QSpinBox;

11 QSlider *slider = new QSlider(Qt::Horizontal);

12 spinBox->setRange(0, 130);

13 slider->setRange(0, 130);

14 QObject::connect(spinBox, SIGNAL(valueChanged(int)),

15 slider, SLOT(setValue(int)));

16 QObject::connect(slider, SIGNAL(valueChanged(int)),

17 spinBox, SLOT(setValue(int)));

18 spinBox->setValue(35);

19 QHBoxLayout *layout = new QHBoxLayout;

20 layout->addWidget(spinBox);

21 layout->addWidget(slider);

22 window->setLayout(layout);

23 window->show();

24 return app.exec();

25 }

Lines 8 and 9 set up the QWidget that will serve as the application's main window. We call

setWindowTitle() to set the text displayed in the window's title bar.

Lines 10 and 11 create a QSpinBox and a QSlider, and lines 12 and 13 set their valid ranges. We can

safely assume that the user is at most 130 years old. We could pass window to the QSpinBox and

QSlider constructors, specifying that these widgets should have window as their parent, but it isn't

necessary here because the layout system will figure this out by itself and automatically set the

parent of the spin box and the slider, as we will see shortly.

The two QObject::connect() calls shown in lines 14 to 17 ensure that the spin box and the slider are

synchronized so that they always show the same value. Whenever the value of one widget changes,

its valueChanged(int) signal is emitted, and the setValue(int) slot of the other widget is called with

the new value.

Line 18 sets the spin box value to 35. When this happens, the QSpinBox emits the valueChanged(int)

signal with an int argument of 35. This argument is passed to the QSlider's setValue(int) slot,

which sets the slider value to 35. The slider then emits the valueChanged(int) signal, because its

own value changed, triggering the spin box's setValue(int) slot. But at this point, setValue(int)

doesn't emit any signal, since the spin box value is already 35. This prevents infinite recursion.

Figure 1.5 summarizes the situation.

Figure 1.5. Changing one widget's value changes both

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