Qt线程初步

默默地EEer，原文地址：

http://www.cnblogs.com/hebaichuanyeah/p/5618781.html

在调用linux环境下线程API写Cpp时，发现异常蛋疼，要么线程函数不能是类的成员函数，要么必须是类的static成员函数（意味着调用的成员变量也必须是static……其实还是不属于类）。

Qt提供一套线程机制，只要继承QThread基类并重新实现void run()函数即可。

新建thread.h继承Qthread，并在thread.cpp中实现它。

thread.h

 

#include "QThread"class Thread : public QThread {Q_OBJECT public:Thread();// void setMessage(const Qstring &message);void setRun();void stop();bool getState(); protected:void run(); private:// QString messageStr;volatile bool enable; signals:void OutMessage(QString message); };

 

 thread.cpp，在run函数中循环1秒触发一个信号输出信息。

 

 

#include "thread.h"Thread::Thread() {enable = true; }void Thread::run() {while(true){if(enable){this->OutMessage(tr("I'm run : thread 1"));msleep(1000);}} } void Thread::stop() {enable = false; } void Thread::setRun() {enable = true; } bool Thread::getState() {return enable; }

 

 mainwindow.h，定义一些Qt控件

#ifndef MAINWINDOW_H #define MAINWINDOW_H#include <QMainWindow> #include <QLabel> #include <QGridLayout> #include <QPushButton> #include <QTextEdit> #include <QDoubleValidator> #include <QComboBox> #include <QTranslator>#include "thread.h"#define PI 3.14592653589class MainWindow : public QMainWindow {Q_OBJECT public:MainWindow();~MainWindow(); private:QWidget* mainWindow;QGridLayout * mainLayout;QTextEdit * messageEdit;QPushButton * clearButton;QPushButton * runStopButton;Thread * backThread; private slots:void updateMessage(QString message);void clearMessage();void runStopThread();};#endif

 mainwindow.cpp

#include "mainwindow.h" #include <QPainter>MainWindow :: MainWindow() {mainWindow = new QWidget;this->setCentralWidget(mainWindow);backThread = new Thread();backThread->start();clearButton = new QPushButton(tr("clear"));clearButton->setSizePolicy(QSizePolicy::Fixed,QSizePolicy::Fixed);runStopButton = new QPushButton(tr("stop"));messageEdit = new QTextEdit();messageEdit->setReadOnly(true);mainLayout = new QGridLayout;mainLayout->addWidget(messageEdit,0,0,5,5);mainLayout->addWidget(clearButton,1,5,1,1);mainLayout->addWidget(runStopButton,0,5,1,1);mainWindow->setLayout(mainLayout);QObject::connect(clearButton,SIGNAL(clicked()),this,SLOT(clearMessage()));QObject::connect(runStopButton,SIGNAL(clicked()),this,SLOT(runStopThread()));QObject::connect(backThread,SIGNAL(OutMessage(QString)),this,SLOT(updateMessage(QString)));this->setWindowTitle(tr("thread test~"));this->resize(QSize(300,100));// this->setFixedSize(200,100); }MainWindow :: ~MainWindow() {mainWindow->deleteLater();mainLayout->deleteLater();messageEdit->deleteLater();clearButton->deleteLater();runStopButton->deleteLater(); }void MainWindow::updateMessage(QString message) {messageEdit->append(message); } void MainWindow::clearMessage() {messageEdit->clear(); } void MainWindow::runStopThread() {if(backThread->getState()){backThread->stop();runStopButton->setText(tr("run"));}else{backThread->setRun();runStopButton->setText(tr("stop"));} }

 运行：

后台线程不断打印信息，通过run/stop按钮停止/启动。

 

同时，Qt提供一套线程同步机制

QMutex（互斥锁），QReadWriteLock（读写锁），QSemaphore（信号量），QWaitCondition（阻塞等待一个条件）。

使用都很简单，其中QWaitCondition，调用bool wait(QMutex *mutex, unsigned long time = ULONG_MAX)成员函数阻塞。 void wakeOne()和void wakeAll()唤醒一处和所有阻塞。（类似于C#里面的ManualResetEvent 类，.WaitOne()   .Set()）

 

转载于:https://www.cnblogs.com/hebaichuanyeah/p/5618781.html

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