一个Qt线程的例子，用于说明QWaitCondition的作用

描述可能比较麻烦，还是直接上代码吧！

main.cpp

[cpp] view plain copy

#include <QApplication>

#include "mainpage.h"

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

{

QApplication a(argc, argv);

MainPage page;

page.show();

return a.exec();

}

mainpage.h

[cpp] view plain copy

#ifndef MAINPAGE_H

#define MAINPAGE_H

#include <QWidget>

#include "thread1.h"

class MainPage : public QWidget

{

Q_OBJECT

public:

explicit MainPage(QWidget *parent = 0);

~MainPage();

thread1 *th1;

private slots:

void doClick();

};

#endif // MAINPAGE_H

thread1.h

[cpp] view plain copy

#ifndef THREAD1_H

#define THREAD1_H

#include <QThread>

#include <QWaitCondition>

#include "thread2.h"

#include <QMutex>

class thread1 : public QThread

{

Q_OBJECT

public:

explicit thread1(QObject *parent = 0);

void run();

void wakeFunc();

private:

QWaitCondition cond;

QMutex mutex;

thread2 th2;

};

#endif // THREAD1_H

thread2.h

[cpp] view plain copy

#ifndef THREAD2_H

#define THREAD2_H

#include <QThread>

class thread2 : public QThread

{

Q_OBJECT

public:

explicit thread2(QObject *parent = 0);

void run();

};

#endif // THREAD2_H

mainpage.cpp

[cpp] view plain copy

#include "mainpage.h"

#include <QDebug>

#include <QPushButton>

MainPage::MainPage(QWidget *parent) :

QWidget(parent)

{

th1=new thread1;

this->resize(100, 40);

QPushButton *pb=new QPushButton("按钮", this);

pb->resize(50, 20);

pb->move(10, 10);

connect(pb, SIGNAL(clicked()), this, SLOT(doClick()));

}

MainPage::~MainPage()

{

}

void MainPage::doClick()

{

qDebug()<<"button clicked!";

th1->wakeFunc();

}

thread1.cpp

[cpp] view plain copy

#include "thread1.h"

#include <QDebug>

thread1::thread1(QObject *parent) :

QThread(parent)

{

}

void thread1::wakeFunc()

{

if(!isRunning()){

start();

}else{

cond.wakeOne();

}

}

void thread1::run()

{

static int x=0;

qDebug()<<"进入thread1的run函数";

while(true){

qDebug()<<"-------> 1 <---------";

mutex.lock();

if(++x>3) th2.start();

qDebug() << "进入thread1的while循环,x值为"<<x;

cond.wait(&mutex); //当处于wait状态时mutex会被暂时释放，并阻塞在这个地方；当线程被cond.wakeOne()等唤醒时，mutex又会被重新锁定，并继续运行

mutex.unlock();

qDebug()<<"-------> 2 <---------";

}

}

thread2.cpp

[cpp] view plain copy

#include "thread2.h"

#include <QDebug>

thread2::thread2(QObject *parent) :

QThread(parent)

{

}

void thread2::run()

{

qDebug()<<"线程2已激活";

}

运行效果：

（1）按钮点击一次时的调试输出



（3）按钮点击多次时的调试输出



结论：借助网友的说法，在debug里面可以看到线程1的run函数只进入了一次，虽然我们调用了它很多次。也就是说使用waitCondition可以让线程进入休眠而不用退出。