Name

Qtimer Signal Slot Car
Qtimer Signal Slot Example
Qtimer Signal Slot Games

Next, its timeout signal is connected to the slot that will do the work, it is started with a value of 1000 milliseconds, indicating that it will time out every second. QTimer also provides a static function for single-shot timers. For example: QTimer:: singleShot(200, this, SLOT(updateCaption)).
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 Clock example).

In this paper, a QTimer is defined, and the slot function onTimeOut is defined as the slot function corresponding to the timeout signal. The code in the constructor of the window class is as follows.

QTimer - Timer signals and single-shot timers

Synopsis

#include <qtimer.h>

Inherits QObject.

Public Members

void timeout ()

Static Public Members

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.

See also start() and isActive().

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.

Qtimer Signal Slot Car

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.

See also start().

Examples:

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.

See Also

Copyright

Qtimer Signal Slot Example

Copyright 1992-2007 Trolltech ASA, http://www.trolltech.com. See the license file included in the distribution for a complete licensestatement.

Author

Generated automatically from the source code.

Bugs

If you find a bug in Qt, please report it as described in http://doc.trolltech.com/bughowto.html. Good bug reports help us to help you. Thank you.

The definitive Qt documentation is provided in HTML format; it is located at $QTDIR/doc/html and can be read using Qt Assistant or with a web browser. Thisman page is provided as a convenience for those users who prefer man pages, although this format is not officially supported by Trolltech.

Qtimer Signal Slot Games

If you find errors in this manual page, please report them to qt-bugs@trolltech.com. Please include the name of the manual page (qtimer.3qt) and theQt version (3.3.8).

Few talk about the use of class QTimer in Qt. This is a small lightweight theme after a series of articles about QSqlTabelModel volume and the resulting consequences of it.

Timers we may need to create a poll LAN devices via TCP / IP stack with certain intervals or hourly data validation or active connections to the server. Yes to anything !? And here we come to the aid QTimer, which we consider the example of output every second time QLabel.

Project structure

We use a minimum of files in our project:

QDataMapperWidget.pro
mainwindow.h - header file of the main application window;
mainwindow.cpp -source window;
main.cpp - the main source file from which the application starts;
mainwindow.ui - form of the main application window;

A draw form in the Designer Qt Creator. But there is nothing to draw. QLabel thrown into the middle and ready.

mainwindow.h

All we need to be happy in this project - a slot that will respond to the operation of a QTimer, but the object of this class.

mainwindow.cpp

And now a few lines to launch the timer. In my comments more than code. Usually so on Assembler`e write - 20% and 80% of the code comments.

Conclusion

As a result, when you start to discover how every moment in time is changing us in the application window