c++ - QTimer 不调用超时槽

Question

我试图在不同的 QThread 中使用 QTimer，但我无法连接到 QTimer 的 timeout () 插槽。

我做错了什么？

这是我的代码:

extern MainWindow *mainClass;

class myObj : public QObject
{
    Q_OBJECT
public:
    explicit myObj(QObject *parent = 0);
    ~myObj();
    QThread workerThread;

    int percent;
    QTimer *percentTimer;

public slots:
    void doWork();
    void percentUpdate();
    void startFunction();

signals:
    void start();
    void UpdateResult();
};

myObj::myObj(QObject *parent) : QObject(parent)
{
    moveToThread(&workerThread);

    connect(&workerThread, SIGNAL(finished()), this, SLOT(deleteLater()));
    connect(this, SIGNAL(UpdateResult()), mainClass, SLOT(on_UpdateResult()));
    connect(&workerThread, SIGNAL(started()), this, SLOT(doWork()));
    connect(this, SIGNAL(start()), this, SLOT(startFunction()));

    percent++;
    percentTimer = new QTimer();
    percentTimer->moveToThread(&workerThread);
    percentTimer->setInterval(1000);
    connect(percentTimer, SIGNAL(timeout()), this,SLOT(percentUpdate()));

}

myObj::~myObj() {
    workerThread.quit();
    workerThread.wait();
    if (percentTimer) percentTimer->deleteLater();
}

void myObj::doWork()
{
    emit start();
    workerThread.exec();    
}

void myObj::startFunction()
{
    percentTimer->start();
    QThread::sleep(60);
    percentTimer->stop();    
}

void myObj::percentUpdate()
{
    qDebug() << "In Timer" << percent++;
    emit UpdateResult();

}

Answer 1

这是因为您试图从与创建它的线程不同的线程启动您的 QTimer。当使用 QTimer 和线程时，在控制它的线程中创建 QTimer 时应该非常小心。

来自 QTimer class documentation :

In multithreaded applications, you can use QTimer in any thread that has an event loop. To start an event loop from a non-GUI thread, use QThread::exec(). Qt uses the timer's thread affinity to determine which thread will emit the timeout() signal. Because of this, you must start and stop the timer in its thread; it is not possible to start a timer from another thread.

在你的情况下 percentTimer = new QTimer(); 是从主线程执行的，(即使你之前使用过 moveToThread ，这仍然是执行它的主线程)，而你的 doWork 和 start 信号是从 workerThread 发出的。

例如，您可以从 workerThread 调用的 void init() 槽执行您的 new QTimer，而不是在构造函数中，确保 QTimer 由正确的线程创建和拥有。

myObj::myObj(QObject *parent) : QObject(parent), percentTimer(nullptr)
{
    moveToThread(&workerThread);

    connect(&workerThread, SIGNAL(finished()), this, SLOT(deleteLater()));
    connect(this, SIGNAL(UpdateResult()), mainClass, SLOT(on_UpdateResult()));
    connect(&workerThread, SIGNAL(started()), this, SLOT(init()));
    connect(&workerThread, SIGNAL(started()), this, SLOT(doWork()));
    connect(this, SIGNAL(start()), this, SLOT(startFunction()));

    percent++;
}

void myObj::init() {
    percentTimer = new QTimer();
    percentTimer->setInterval(1000);
    connect(percentTimer, SIGNAL(timeout()), this, SLOT(percentUpdate()));
}