QMutexLocker測試

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QThread>

class ThreadA : public QThread
{
public:
    ThreadA () {}
    void run();
};

class ThreadB : public QThread
{
public:
    ThreadB () {}
    void run();
};


namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private slots:
    void on_pushButton_clicked();
    void on_pushButton_2_clicked();

private:
    Ui::MainWindow *ui;
    ThreadA m_a;
    ThreadB m_b;
};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QtDebug>
#include <QTime>
#include <QMutex>
QMutex mutex;
int num;

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    num = 0 ;
}

MainWindow::~MainWindow()
{
    delete ui;
}

void ThreadA::run()
{
    while(1)
    {
        QMutexLocker lock(&mutex);
        num++;
        qDebug() << QString::number(num);
        QTime t;
        t.start();
        while(t.elapsed() < 5000)
            QCoreApplication::processEvents();
    }
}


void ThreadB::run()
{
    while(1)
    {
        QMutexLocker lock(&mutex);
        num--;
        qDebug() << QString::number(num);
        QTime t;
        t.start();
        while(t.elapsed() < 1000)
            QCoreApplication::processEvents();
    }
}

void MainWindow::on_pushButton_clicked()
{
    m_a.start();
}

void MainWindow::on_pushButton_2_clicked()
{
    m_b.start();
}

QMutexLocker 定義成局部變量，當局部變量釋放時會調用QMutexLocker的析構函數，析構函數會調用解鎖操作
源碼：

    inline ~QMutexLocker() { unlock(); }

    inline void unlock() Q_DECL_NOTHROW
    {
        if ((val & quintptr(1u)) == quintptr(1u)) {
            val &= ~quintptr(1u);
            mutex()->unlock();
        }
    }