QTimer isActive returns true，但 remainingTime returns -1

Question

开始时定义并启动了一个定时器：

QTimer *teleTimer;
teleTimer = new QTimer();
QObject::connect(teleTimer, SIGNAL(timeout()), this, SLOT(somefunction1())); 
teleTimer->start(200);

然后它在某处停止并调用另一个函数somefunction2()。该功能完成后，计时器再次启动：

if (teleTimer->isActive())
{
    qDebug() << teleTimer->remainingTime();
    teleTimer->stop();
    delete teleTimer;
}
teleTimer = new QTimer();
QObject::connect(teleTimer, SIGNAL(timeout()), this, SLOT(somefunction3())); 
teleTimer->start(200);

然而，teleTimer->isActive()returnstrue，而teleTimer->remainingTime()returns-1，则应用程序崩溃：

Thread 2 Crashed:: QThread
0   org.qt-project.QtCore           0x000000010ed4be3b QObject::killTimer(int) + 27
1   org.qt-project.QtCore           0x000000010ed5a9b9 QTimer::stop() + 25
2   com.yourcompany.QTGCS           0x000000010dffa609 TelemetrySerialWorker::setTelemetryMode(int) + 745 (telemetryserialworker.cpp:114)

那么如何解决这个问题呢？谢谢。

更新：此问题已解决。感谢所有的答复。下次我会尝试 post 一个好的格式的问题。谢谢。

Answer 1

在@eyllanesc的提示下，我的问题终于解决了

一开始我用的是delete teleTimer然后我的程序就开始崩溃了。当时我认为原因是当这个函数再次调用时定时器并没有真正停止。然后我将我的代码更改为运行另一个单发计时器，这样它就真的有一个计时器可以停止了。

最开始：（崩溃）

void timerSwitch()
{
    if (teleTimer->isActive())
    {
        qDebug() << teleTimer->remainingTime();
        teleTimer->stop();
        delete teleTimer;
    }
    if (mode == 1)
    {
        teleTimer = new QTimer();
        QObject::connect(teleTimer, SIGNAL(timeout()), this, SLOT(somefunction())); 
        teleTimer->start(200);
    }
    else if (mode == 2)
    {
        somefunction2();
    }

}

第一次更改：（崩溃）

void timerSwitch()
{
    if (teleTimer->isActive())
    {
        qDebug() << teleTimer->remainingTime();
        teleTimer->stop();
        delete teleTimer;
    }
    if (mode == 1)
    {
        teleTimer = new QTimer();
        QObject::connect(teleTimer, SIGNAL(timeout()), this, SLOT(somefunction())); 
        teleTimer->start(200);
    }
    else if (mode == 2)
    {
        teleTimer = new QTimer();
        teleTimer.singleshot(..., ..., SLOT(somefunction2()));
    }

}

然后根据@eyllanesc 的提示，我将代码更改为：

void timerSwitch()
{
    if (teleTimer->isActive())
    {
        qDebug() << teleTimer->remainingTime();
        teleTimer->stop();
        teleTimer->deleteLater();
    }
    if (mode == 1)
    {
        teleTimer = new QTimer();
        QObject::connect(teleTimer, SIGNAL(timeout()), this, SLOT(somefunction())); 
        teleTimer->start(200);
    }
    else if (mode == 2)
    {
        teleTimer = new QTimer();
        teleTimer.singleshot(..., ..., SLOT(somefunction2()));
    }

}

我的程序仍然崩溃。

然后我将代码更改为：

void timerSwitch()
{
    if (teleTimer->isActive())
    {
        qDebug() << teleTimer->remainingTime();
        teleTimer->stop();
        teleTimer->deleteLater();
    }
    if (mode == 1)
    {
        teleTimer = new QTimer();
        QObject::connect(teleTimer, SIGNAL(timeout()), this, SLOT(somefunction())); 
        teleTimer->start(200);
    }
    else if (mode == 2)
    {
        somefunction2();
    }

}

这次我的程序运行正常。我测试了20多次，都正常工作，没有崩溃。

在这个过程中，我的电脑给出的所有原因都是类似这样的：

Thread 2 Crashed:: QThread
0   org.qt-project.QtCore           0x000000010ed4be3b QObject::killTimer(int) + 27
1   org.qt-project.QtCore           0x000000010ed5a9b9 QTimer::stop() + 25
2   com.yourcompany.QTGCS           0x000000010dffa609 TelemetrySerialWorker::setTelemetryMode(int) + 745 (telemetryserialworker.cpp:114)

我认为错误来自 stop()，因为 isActive() returns true，但是 remainingTime() returns -1.我的理解是在调用isActive()的时候，定时器确实没有停止，但是在调用remainingTime()的时候，定时器停止了。然后我觉得这不应该这么愚蠢。我仍然有疑问，但我的问题已经解决了。当我有时间时，我会更新更多细节。谢谢各位大侠回复我

Answer 2

一般来说，如果您按顺序调用函数，最简单的方法是将顺序保持在 table 中，并使用单次定时器。重新创建计时器或连接很昂贵。

#include <QtCore>
#include <functional>
#include <initializer_list>

class Sequencer : public QObject {
public:
  using base_class = QObject;
  struct Element {
    int delay = 0;
    std::function<void()> functor;
  };
  explicit Sequencer(QObject *parent = {}) : QObject(parent) {}
  // takes care of initializer list and other compatible initializers
  Sequencer(QVector<Element> init, QObject *parent = {}) : 
    QObject(parent), m_sequence(std::move(init)) {}
  void start(int index = 0) {
    m_it = m_sequence.begin() + index;
    m_timer.start(m_it->delay, this);
  }
  int stop() {
    m_timer.stop();
    return m_it - m_sequence.begin();
  }
protected:
  void timerEvent(QTimerEvent *event) override {
    if (m_timer.timerId() != event->timerId())
      return base_class::timerEvent(event);
    m_it->functor();
    m_it++;
    if (m_it != m_sequence.end())
      m_timer.start(m_it->delay, this);
    else
      m_timer.stop();
  }
private:
  QVector<Element> m_sequence;
  QVector<Element>::const_iterator m_it = m_sequence.begin();     
  QBasicTimer m_timer;
};

您可以这样使用它，例如：

class MyClass { // can be QObject, but doesn't have to be
  Sequence m_seq{
    {200, [=]{ function1(); }},   // after 200ms delay
    {0,   [=]{ function2(); }},   // after no delay
    {500, [=]{ function3(); }},   // after 500ms delay
    {0,   [=]{ loop(); }}};       // and right away loop the sequence
  void function1();
  void function2();
  void function3();
  void loop() { m_seq.start(); }
public:
  MyClass() {
    m_seq.start();
  }
};

QTimer isActive returns true，但 remainingTime returns -1

QTimer isActive returns true, but remainingTime returns -1

c++

qt

qtimer