QT多線程使用

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QThread

繼承QThread類構建線程，可以使用信號槽通信

class Thread : public QThread
{
	Q_OBJECT
public：
	void setStop();
protected:
	void run();
signals:
    void sgl_SendMsg(); //自己的信號，可在線程進行中發送消息
private:
	bool m_isStopped;	//保證線程正常結束
};


void Thread::run()
{
	while(!m_isStopped)
	{
		//主體
	}
	m_isStopped = false;
}

void Thread::setStop()
{
	m_isStopped = true;
}

QThreadPool

Qt的線程池
You may need to create and destroy threads frequently, as managing QThread instances by hand can become cumbersome. For this, you can use the QThreadPool class, which manages a pool of reusable QThreads.
——《Mastring Qt5》

#include <QCoreApplication>
#include <QObject>
#include <QRunnable>
#include <QThread>
#include <QThreadPool>
#include <QDebug>

class HelloWorldTask : public QRunnable 
{
    // 線程執行任務：每間隔10s打印出線程的信息
    void run()
    {
        qDebug() << QThread::currentThread();
        QThread::msleep(10000);
    }
};


int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    QThreadPool::globalInstance()->setMaxThreadCount(8);
    for (int nNum = 0; nNum < 100; nNum++)
    {
        HelloWorldTask	 *task = new HelloWorldTask;
        QThreadPool::globalInstance()->start(task);
    }
    return a.exec();
}

Qt Concurrent

Another approach to multi-threaded development is available with the Qt Concurrent framework. It is a higher-level API that avoids the use of mutexes/lock/wait conditions and promotes the distribution of the processing among CPU cores.
——《Mastring Qt5》
函數級別的多線程。當界面操作比較費時時，可使用Qt Concurrent將邏輯放在新線程中防止界面卡頓。

QFutureWatcher<void> watcher;
void longRunningFunction();
QFuture<void> future;	//QFuture 用來返回QtConcurrent::run（）的執行結果
 future = QtConcurrent::run(longRunningFunction); //將會在默認的線程池中獲取一個線程來執行函數函數longRunningFunction()
watcher.setFuture(future); //用來監視函數結果