Qt 4.8: QML Timer Element

Qt Reference Documentation

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# QML Timer Element

The Timer item triggers a handler at a specified interval. More...

This element was introduced in Qt 4.7.

- List of all members, including inherited members

## Properties

- interval : int
- repeat : bool
- running : bool
- triggeredOnStart : bool

## Signal Handlers

- onTriggered

## Methods

- restart
- start
- stop

## Detailed Description

A Timer can be used to trigger an action either once, or repeatedly at a given interval.

Here is a Timer that shows the current date and time, and updates the text every 500 milliseconds. It uses the JavaScript `Date` object to access the current time.

     import QtQuick 1.0

     Item {
         Timer {
             interval: 500; running: true; repeat: true
             onTriggered: time.text = Date().toString()
         }

         Text { id: time }
     }

The Timer element is synchronized with the animation timer. Since the animation timer is usually set to 60fps, the resolution of Timer will be at best 16ms.

If the Timer is running and one of its properties is changed, the elapsed time will be reset. For example, if a Timer with interval of 1000ms has its repeat property changed 500ms after starting, the elapsed time will be reset to 0, and the Timer will be triggered 1000ms later.

See also Clocks example.

## Property Documentation

interval : int

Sets the interval between triggers, in milliseconds.

The default interval is 1000 milliseconds.

repeat : bool

If repeat is true the timer is triggered repeatedly at the specified interval; otherwise, the timer will trigger once at the specified interval and then stop (i.e. running will be set to false).

repeat defaults to false.

See also running.

running : bool

If set to true, starts the timer; otherwise stops the timer. For a non-repeating timer, running is set to false after the timer has been triggered.

running defaults to false.

See also repeat.

triggeredOnStart : bool

When a timer is started, the first trigger is usually after the specified interval has elapsed. It is sometimes desirable to trigger immediately when the timer is started; for example, to establish an initial state.

If triggeredOnStart is true, the timer is triggered immediately when started, and subsequently at the specified interval. Note that if repeat is set to false, the timer is triggered twice; once on start, and again at the interval.

triggeredOnStart defaults to false.

See also running.

## Signal Handler Documentation

Timer::onTriggered ()

This handler is called when the Timer is triggered.

## Method Documentation

Timer::restart ()

Restarts the timer.

If the Timer is not running it will be started, otherwise it will be stopped, reset to initial state and started. The `running` property will be true following a call to `restart()`.

Timer::start ()

Starts the timer.

If the timer is already running, calling this method has no effect. The `running` property will be true following a call to `start()`.

Timer::stop ()

Stops the timer.

If the timer is not running, calling this method has no effect. The `running` property will be false following a call to `stop()`.