c++ - 有什么方法可以识别调用了哪个 QTimer？

Question

我考虑过为回调提供额外的参数，但这看起来太复杂了(创建自己的修改后的 QTimer 对象等)

读完 QTimer docs 后我想到的另一件事正在保存 timerID 并检查它，但由于回调中没有任何内容，我不知道要检查什么:/

如果有人对特殊用例感兴趣: https://github.com/Bluscream/pyTSon_plugins/blob/master/scripts/antiAFK/init.py#L35

Answer 1

我可以想到至少两种您可以采用的方法:

首先，您可以通过在插槽中转换发送者来检索指向 QTimer 的指针:

class MyClass : public QObject
{
    Q_OBJECT
public:
    MyClass(QObject * parent = 0);
    <...>
private Q_SLOTS:
    void onTimerFired();
private:
    void doSomethingAndStartTimer();
private:
    int m_firstTimerId;
    int m_secondTimerId;
};

void MyClass::doSomethingAndStartTimer()
{
    <...>
    QTimer *timer = new QTimer(this);
    m_firstTimerId = timer->timerId();
    connect(timer, SIGNAL(timeout()), this, SLOT(onTimerFired()));
    timer->start();
    <..>
}

void MyClass::onTimerFired()
{
    QTimer * timer = qobject_cast<QTimer*>(sender());
    if (timer) {
        if (timer->timerId() == m_firstTimerId) {
            <...> // Process it somehow
        }
        else if (timer->timerId() == m_secondTimerId) {
            <...> // Process it some other way
        }
    }
}

其次，您可以放弃显式的 QTimer 用法，而是使用 startTimer以及重新实现类的 timerEvent 方法，该方法接收 QTimerEvent，您可以从中获取计时器 ID

class MyClass : public QObject
{
    Q_OBJECT
public:
    MyClass(QObject * parent = 0);
    <...>
private:
    virtual void timerEvent(QTimerEvent * event);
private:
    void doSomethingAndStartTimer();
private:
    int m_firstTimerId;
    int m_secondTimerId;
};

void MyClass::doSomethingAndStartTimer()
{
    <...>
    int interval = 100; // 100 msec
    m_firstTimerId = startTimer(interval);
    <...>
}

void MyClass::timerEvent(QTimerEvent * event)
{
    if (event->timerId() == m_firstTimerId) {
        <...> // process it somehow
    }
    else if (event->timerId() == m_secondTimerId) {
        <...> // process it some other way
    }
}

第二种方法在 documentation 中提到对于 QTimer:

Alternatives to QTimer

An alternative to using QTimer is to call QObject::startTimer() for your object and reimplement the QObject::timerEvent() event handler in your class (which must inherit QObject). The disadvantage is that timerEvent() does not support such high-level features as single-shot timers or signals.