QTimer Class

Member Function Documentation

This static function calls functor after msec milliseconds.

It is very convenient to use this function because you do not need to bother with a timerEvent or create a local QTimer object.

If context is specified, then the functor will be called only if the context object has not been destroyed before the interval occurs. The functor will then be run the thread of context. The context's thread must have a running Qt event loop.

If functor is a member function of context, then the function will be called on the object.

The msec parameter can be an int or a std::chrono::milliseconds value.

Note: This function is reentrant.

See also start().

[explicit] QTimer::QTimer(QObject *parent = nullptr)

Constructs a timer with the given parent.

[virtual noexcept] QTimer::~QTimer()

Destroys the timer.

template <typename Functor> QMetaObject::Connection QTimer::callOnTimeout(Functor &&slot)

Creates a connection from the timer's timeout() signal to slot. Returns a handle to the connection.

This method is provided for convenience. It's equivalent to calling:

QObject::connect(timer, &QTimer::timeout, timer, slot, Qt::DirectConnection);

See also QObject::connect() and timeout().

template <typename Functor> QMetaObject::Connection QTimer::callOnTimeout(const QObject *context, Functor &&slot, Qt::ConnectionType connectionType = Qt::AutoConnection)

This function overloads callOnTimeout().

Creates a connection from the timeout() signal to slot to be placed in a specific event loop of context, and returns a handle to the connection.

This method is provided for convenience. It's equivalent to calling:

QObject::connect(timer, &QTimer::timeout, context, slot, connectionType);

See also QObject::connect() and timeout().

std::chrono::milliseconds QTimer::intervalAsDuration() const

Returns the interval of this timer as a std::chrono::milliseconds object.

See also interval.

bool QTimer::isActive() const

Returns true if the timer is running (pending); otherwise returns false.

std::chrono::milliseconds QTimer::remainingTimeAsDuration() const

Returns the time remaining in this timer object as a std::chrono::milliseconds object. If this timer is due or overdue, the returned value is std::chrono::milliseconds::zero(). If the remaining time could not be found or the timer is not active, this function returns a negative duration.

See also remainingTime().

[static] void QTimer::singleShot(int msec, const QObject *receiver, const char *member)

This static function calls a slot after a given time interval.

It is very convenient to use this function because you do not need to bother with a timerEvent or create a local QTimer object.

Example:

#include <QApplication>
#include <QTimer>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QTimer::singleShot(600000, &app, QCoreApplication::quit);
    ...
    return app.exec();
}

This sample program automatically terminates after 10 minutes (600,000 milliseconds).

The receiver is the receiving object and the member is the slot. The time interval is msec milliseconds.

Note: This function is reentrant.

See also setSingleShot() and start().

[static] void QTimer::singleShot(int msec, Qt::TimerType timerType, const QObject *receiver, const char *member)

This is an overloaded function.

This static function calls a slot after a given time interval.

It is very convenient to use this function because you do not need to bother with a timerEvent or create a local QTimer object.

The receiver is the receiving object and the member is the slot. The time interval is msec milliseconds. The timerType affects the accuracy of the timer.

Note: This function is reentrant.

See also start().

[static] void QTimer::singleShot(std::chrono::milliseconds msec, const QObject *receiver, const char *member)

This is an overloaded function.

This static function calls a slot after a given time interval.

It is very convenient to use this function because you do not need to bother with a timerEvent or create a local QTimer object.

The receiver is the receiving object and the member is the slot. The time interval is given in the duration object msec.

Note: This function is reentrant.

See also start().

[static] void QTimer::singleShot(std::chrono::milliseconds msec, Qt::TimerType timerType, const QObject *receiver, const char *member)

This is an overloaded function.

This static function calls a slot after a given time interval.

It is very convenient to use this function because you do not need to bother with a timerEvent or create a local QTimer object.

The receiver is the receiving object and the member is the slot. The time interval is given in the duration object msec. The timerType affects the accuracy of the timer.

Note: This function is reentrant.

See also start().

[slot] void QTimer::start(int msec)

Starts or restarts the timer with a timeout interval of msec milliseconds.

If the timer is already running, it will be stopped and restarted.

If singleShot is true, the timer will be activated only once. This is equivalent to:

timer.setInterval(msec);
timer.start();

[slot] void QTimer::start()

This function overloads start().

Starts or restarts the timer with the timeout specified in interval.

If the timer is already running, it will be stopped and restarted.

If singleShot is true, the timer will be activated only once.

void QTimer::start(std::chrono::milliseconds msec)

This is an overloaded function.

Starts or restarts the timer with a timeout of duration msec milliseconds.

If the timer is already running, it will be stopped and restarted.

If singleShot is true, the timer will be activated only once. This is equivalent to:

timer.setInterval(msec);
timer.start();

[slot] void QTimer::stop()

Stops the timer.

See also start().

[private signal] void QTimer::timeout()

This signal is emitted when the timer times out.

See also interval, start(), and stop().

[override virtual protected] void QTimer::timerEvent(QTimerEvent *e)

Reimplements: QObject::timerEvent(QTimerEvent *event).

int QTimer::timerId() const

Returns the ID of the timer if the timer is running; otherwise returns -1.