Qtimer Signal Slot

Posted on 4/13/202222.08.2017by admin

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Qtimer Signal Slot Example
Qt Qtimer Signal Slot
Qtimer Signal Slot Games

Name

QTimer - Timer signals and single-shot timers

Synopsis

QtCore.SIGNAL and QtCore.SLOT macros allow Python to interface with Qt signal and slot delivery mechanisms. This is the old way of using signals and slots. The example below uses the well known clicked signal from a QPushButton. The connect method has a non python-friendly syntax. It is necessary to inform the object, its signal (via macro. Signals and slots were one of the distinguishing features that made Qt an exciting and innovative tool back in time. But sometimes you can teach new tricks to an old dog, and QObjects gained a new way to connect between signals and slots in Qt5, plus some extra features to connect to other functions which are not slots. Detailed Description. The QTimer class provides repetitive and single-shot timers. The QTimer class provides a high-level programming interface for timers. To use it, create a QTimer, connect its timeout signal to the appropriate slots, and call start. From then on, it will emit the timeout signal at constant intervals. Example for a one second (1000 millisecond) timer (from the Analog. To guarantee that QTimers are actually created in the new thread there a few options, but one of the easier ways are by connecting the signal started from QThread to an appropriate slot of the class which should hold the QTimer. Our example will consist of a class named CyclicWorker which has a slot called Initialize which will create the QTimer. The following are 30 code examples for showing how to use PyQt5.QtCore.QTimer.singleShot.These examples are extracted from open source projects. You can vote up the ones you like or vote down the ones you don't like, and go to the original project or source file by following the links above each example.

#include <qtimer.h>

Inherits QObject.

Public Members

void timeout ()

Static Public Members

The QTimer class provides timer signals and single-shot timers.

It uses timer events internally to provide a more versatile timer. QTimer is very easy to use: create a QTimer, call start() to start it and connect itstimeout() to the appropriate slots. When the time is up it will emit the timeout() signal.

Note that a QTimer object is destroyed automatically when its parent object is destroyed.

Example:You can also use the static singleShot() function to create a single shot timer.

As a special case, a QTimer with timeout 0 times out as soon as all the events in the window system's event queue have been processed.

This can be used to do heavy work while providing a snappy user interface:myObject->processOneThing() will be called repeatedly and should return quickly (typically after processing one data item) so that Qt can deliver eventsto widgets and stop the timer as soon as it has done all its work. This is the traditional way of implementing heavy work in GUI applications; multi-threadingis now becoming available on more and more platforms, and we expect that null events will eventually be replaced by threading.

Note that QTimer's accuracy depends on the underlying operating system and hardware. Most platforms support an accuracy of 20ms; some provide more. If Qt isunable to deliver the requested number of timer clicks, it will silently discard some.

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

Some operating systems limit the number of timers that may be used; Qt tries to work around these limitations.

See also Event Classes and Time and Date.

Member Function Documentation

QTimer::QTimer ( QObject * parent = 0, const char * name = 0 )

Constructs a timer called name, with the parent parent.

Note that the parent object's destructor will destroy this timer object.

QTimer::~QTimer ()

Destroys the timer.

void QTimer::changeInterval ( int msec )

Changes the timeout interval to msec milliseconds.

If the timer signal is pending, it will be stopped and restarted; otherwise it will be started.

bool QTimer::isActive () const

Returns TRUE if the timer is running (pending); otherwise returns FALSE.

Example: t11/cannon.cpp.

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

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 to create a local QTimer object.

Example:This sample program automatically terminates after 10 minutes (i.e. 600000 milliseconds).

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

int QTimer::start ( int msec, bool sshot = FALSE )

Starts the timer with a msec milliseconds timeout, and returns the ID of the timer, or zero when starting the timer failed.

If sshot is TRUE, the timer will be activated only once; otherwise it will continue until it is stopped.

Any pending timer will be stopped.

See also singleShot(), stop(), changeInterval(), and isActive().

Examples:

void QTimer::stop ()

Stops the timer.

void QTimer::timeout () [signal]

This signal is emitted when the timer is activated.

Examples:

int QTimer::timerId () const

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

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