Q_OBJECT宏的作用

The Q_OBJECT macro at the beginning of the class definition is necessary for all classes that define signals or slots
只有加入了Q_OBJECT，你才能使用QT中的signal和slot机制

QT的信号与槽机制介绍

A Small Example

A minimal C++ class declaration might read:

class Counter

{

public:

Counter() { m_value = 0; }

int value() const { return m_value; }

void setValue(int value);

private:

int m_value;

};

A small QObject-based class might read:

#include <QObject>

class Counter : public QObject

{

Q_OBJECT

public:

Counter() { m_value = 0; }

int value() const { return m_value; }

public slots:

void setValue(int value);

signals:

void valueChanged(int newValue);

private:

int m_value;

};

比如编写事件接口等程序时，有时会出现如下问题：
在PC端成功编译，但在开发板端却显示错误：
    QObject::connect: No such slot QWidget::*******()                             
    QObject::connect: (sender name:   'unnamed')                                   
    QObject::connect: (receiver name: 'unnamed')

这时候，就必须在头文件派生类的时候，首先像下面那样引入Q_OBJECT宏：
    class MyMainWindow : public QWidget
    {
        Q_OBJECT
    ......
    }