本文主要是介绍信号的转发 QSignalMapper,mutex 和waitcondition的使用(QtSdk--threads/movedobject)，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
重点练习 信号的转发 QSignalMapper,mutex 和waitcondition的使用#include <QtCore>
#include "workerobject.h"
#include "thread.h"
/*
* moves a class derived from QObject (WorkerObject) to another thread
* and calls methods over thread boundaries.
//invokeMethod的用法为，尝试调用对象obj的方法member（注意member可以为信号或者是槽)，
//如何member可以被调用，则返回真，否则返回假。QMetaObject::invokeMethod可以是异步调用，
//也可以是同步调用。这取决与它的连接方式Qt::ConnectionType type。
//如果type为Qt::DirectConnection，则为同步调用，若为Qt::QueuedConnection，则为异步调用。
执行流程：
1，定义一个thread （把开始信号发到mapper上） 和一个object（init一个定时器）
2，把object move到 thread中，然后把mapper中的信号，投递到一个函数中，并waitcondition和mutex上，这样这个thread就锁住了，直到退出为止，
3，使用 QMetaObject::invokeMethod机制开始object对象的运行。
4，定时3000ms后程序退出，这个可以不要。
5，调用thread中的stop函数，这样通过之前设置的mapper，中转到真正退出函数，然后退出。
6 结束。
*/
// movedobject/main.cpp
int main(int argc, char *argv[])
{
QCoreApplication app(argc, argv);
Thread thread; //这个是自己定义的线程，QT的api是QThread
qDebug() << "main thread ID: " << app.thread()->currentThreadId();
WorkerObject *worker = new WorkerObject;
thread.launchWorker(worker);//把workermove到这个线程中
QMetaObject::invokeMethod(worker, "doWork", Qt::QueuedConnection);//异步调用
QMetaObject::invokeMethod(worker, "startPolling", Qt::QueuedConnection, Q_ARG(int, 500));//暂时不知道Q_ARG干嘛用的
//let application produce output for 3 seconds and quit
QTimer::singleShot(3000, &app, SLOT(quit()));///3000ms后自动退出。
app.exec();
thread.stop();
thread.wait();
delete worker;
return 0;
}
----------------------------------------------------
#ifndef THREAD_H
#define THREAD_H
#include <QtCore>
class Thread :public QThread
{
Q_OBJECT
public:
Thread( QObject *parent=0);
~Thread();
void stop();
void launchWorker(QObject *worker);
private:
QObject *worker;
QSignalMapper *shutDownHelper;//定义一个信号转发器
QWaitCondition waitCondition;//等待条件对象，就是一个线程等待另一个线程的唤醒，用来同步某个操作。
QMutex mutex;
private slots:
void stopExecutor();
void setReadyStatus();
signals:
void aboutToStop();
};
#endif // THREAD_H
-----------------------------------------------------
#ifndef WORKEROBJECT_H
#define WORKEROBJECT_H
#include <QtCore>
class WorkerObject : public QObject
{
Q_OBJECT
public:
explicit WorkerObject(QObject *parent = 0);
~WorkerObject();
public slots:
void doWork();
void startPolling(int milliseconds);
void stopPolling();
private slots:
void poll();
private:
QTimer *timer;
int count;
};
#endif // WORKEROBJECT_H
-----------------------------------------------------
#include "thread.h"
/*
* QThread derived class with additional capability to move a QObject to the
* new thread, to stop the thread and move the QObject back to the thread where
*it came from.
*/
Thread::Thread( QObject *parent)
: QThread (parent)
{
//we need a class that receives signals from other threads and emits a signal in response
shutDownHelper=new QSignalMapper;
shutDownHelper->setMapping(this,0);
connect(this, SIGNAL(started()), this, SLOT(setReadyStatus() ), Qt::DirectConnection);
connect(this, SIGNAL(aboutToStop()), shutDownHelper, SLOT(map()) );//发到中转站
}
//------------------------------------------------------
Thread::~Thread()
{
delete shutDownHelper;
}
//------------------------------------------------------
// starts thread, moves worker to this thread and blocks
//使用QObject::moveToThread()可以将QObject对象从一个线程移动到另一个线程。
void Thread::launchWorker(QObject *worker)
{
worker = worker;//前一个worker是成员变量
start();
int i=0;
worker->moveToThread(this);//把worker线程move到这个线程中来。
shutDownHelper->moveToThread(this);
///中转站 转到具体的函数中
connect(shutDownHelper, SIGNAL(mapped(int) ), this, SLOT(stopExecutor()), Qt::DirectConnection );
mutex.lock();
waitCondition.wait(&mutex);//锁定等待。。
}
//------------------------------------------------------
// puts a command to stop processing in the event queue of worker thread
void Thread::stop()
{
emit aboutToStop();//发送这个信号。
}
//------------------------------------------------------
// methods above this line should be called in gui thread context
// methods below this line are private and will be run in secondary thread context
//------------------------------------------------------
void Thread::stopExecutor() //secondary thread context
{
exit();
}
//------------------------------------------------------
void Thread::setReadyStatus()
{
waitCondition.wakeAll();
}
-----------------------------------------------------
-----------------------------------------------------
-----------------------------------------------------
// movedobject/main.cpp
int main(int argc, char *argv[])
{
QCoreApplication app(argc, argv);
Thread thread; //这个是自己定义的线程，QT的api是QThread
qDebug() << "main thread ID: " << app.thread()->currentThreadId();
WorkerObject *worker = new WorkerObject;
thread.launchWorker(worker);//把workermove到这个线程中
QMetaObject::invokeMethod(worker, "doWork", Qt::QueuedConnection);//异步调用
QMetaObject::invokeMethod(worker, "startPolling", Qt::QueuedConnection, Q_ARG(int, 500));//暂时不知道Q_ARG干嘛用的
//let application produce output for 3 seconds and quit
QTimer::singleShot(3000, &app, SLOT(quit()));///3000ms后自动退出。
app.exec();
thread.stop();
thread.wait();
delete worker;
return 0;
}
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#include <QtCore>
#include "workerobject.h"
/*
* represents an object that lives in another thread where it polls a resource
* and communicates with the gui thread
*/
WorkerObject::WorkerObject(QObject *parent)
: QObject(parent)
{
timer = new QTimer(this);
connect(timer, SIGNAL(timeout()), this, SLOT(poll()));
}
//---------------------------------------------------------------
void WorkerObject::doWork()
{
qDebug() << "doing work in thread " << thread()->currentThreadId() ;
}
//---------------------------------------------------------------
WorkerObject::~WorkerObject()
{
qDebug() << "destruction WorkerObject in thread " << thread()->currentThreadId();
}
//---------------------------------------------------------------
void WorkerObject::startPolling(int milliseconds)
{
count=0;
timer->start(milliseconds);//定时器的时间间隔。
}
//---------------------------------------------------------------
void WorkerObject::stopPolling()
{
timer->stop();
}
//---------------------------------------------------------------
void WorkerObject::poll()
{
qDebug() << QString("timer hit %1").arg(count);
count++;
}
------------------------------------------------------
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