QThread(3qt)QThread(3qt)NAME
QThread - Platform-independent threads
SYNOPSIS
All the functions in this class are thread-safe when Qt is built with
thread support.</p>
#include <qthread.h>
Inherits Qt.
Public Members
QThread ( unsigned int stackSize = 0 )
virtual ~QThread ()
bool wait ( unsigned long time = ULONG_MAX )
enum Priority { IdlePriority, LowestPriority, LowPriority,
NormalPriority, HighPriority, HighestPriority,
TimeCriticalPriority, InheritPriority }
void start ( Priority priority = InheritPriority )
void terminate ()
bool finished () const
bool running () const
Static Public Members
Qt::HANDLE currentThread ()
void postEvent ( QObject * receiver, QEvent * event ) (obsolete)
void exit ()
Protected Members
virtual void run () = 0
Static Protected Members
void sleep ( unsigned long secs )
void msleep ( unsigned long msecs )
void usleep ( unsigned long usecs )
DESCRIPTION
The QThread class provides platform-independent threads.
A QThread represents a separate thread of control within the program;
it shares data with all the other threads within the process but
executes independently in the way that a separate program does on a
multitasking operating system. Instead of starting in main(), QThreads
begin executing in run(). You inherit run() to include your code. For
example:
class MyThread : public QThread {
public:
virtual void run();
};
void MyThread::run()
{
for( int count = 0; count < 20; count++ ) {
sleep( 1 );
qDebug( "Ping!" );
}
}
int main()
{
MyThread a;
MyThread b;
a.start();
b.start();
a.wait();
b.wait();
}
This will start two threads, each of which writes Ping! 20 times to the
screen and exits. The wait() calls at the end of main() are necessary
because exiting main() ends the program, unceremoniously killing all
other threads. Each MyThread stops executing when it reaches the end of
MyThread::run(), just as an application does when it leaves main().
See also Thread Support in Qt, Environment Classes, and Threading.
Member Type Documentation
QThread::Priority
This enum type indicates how the operating system should schedule newly
created threads.
QThread::IdlePriority - scheduled only when no other threads are
running.
QThread::LowestPriority - scheduled less often than LowPriority.
QThread::LowPriority - scheduled less often than NormalPriority.
QThread::NormalPriority - the default priority of the operating system.
QThread::HighPriority - scheduled more often than NormalPriority.
QThread::HighestPriority - scheduled more often then HighPriority.
QThread::TimeCriticalPriority - scheduled as often as possible.
QThread::InheritPriority - use the same priority as the creating
thread. This is the default.
MEMBER FUNCTION DOCUMENTATIONQThread::QThread ( unsigned int stackSize = 0 )
Constructs a new thread. The thread does not begin executing until
start() is called.
If stackSize is greater than zero, the maximum stack size is set to
stackSize bytes, otherwise the maximum stack size is automatically
determined by the operating system.
Warning: Most operating systems place minimum and maximum limits on
thread stack sizes. The thread will fail to start if the stack size is
outside these limits.
QThread::~QThread () [virtual]
QThread destructor.
Note that deleting a QThread object will not stop the execution of the
thread it represents. Deleting a running QThread (i.e. finished()
returns FALSE) will probably result in a program crash. You can wait()
on a thread to make sure that it has finished.
Qt::HANDLE QThread::currentThread () [static]
This returns the thread handle of the currently executing thread.
Warning: The handle returned by this function is used for internal
purposes and should not be used in any application code. On Windows,
the returned value is a pseudo handle for the current thread, and it
cannot be used for numerical comparison.
void QThread::exit () [static]
Ends the execution of the calling thread and wakes up any threads
waiting for its termination.
bool QThread::finished () const
Returns TRUE if the thread is finished; otherwise returns FALSE.
void QThread::msleep ( unsigned long msecs ) [static protected]
System independent sleep. This causes the current thread to sleep for
msecs milliseconds
void QThread::postEvent ( QObject * receiver, QEvent * event ) [static]
This function is obsolete. It is provided to keep old source working.
We strongly advise against using it in new code.
Use QApplication::postEvent() instead.
void QThread::run () [pure virtual protected]
This method is pure virtual, and must be implemented in derived classes
in order to do useful work. Returning from this method will end the
execution of the thread.
See also wait().
bool QThread::running () const
Returns TRUE if the thread is running; otherwise returns FALSE.
void QThread::sleep ( unsigned long secs ) [static protected]
System independent sleep. This causes the current thread to sleep for
secs seconds.
void QThread::start ( Priority priority = InheritPriority )
Begins execution of the thread by calling run(), which should be
reimplemented in a QThread subclass to contain your code. The operating
system will schedule the thread according to the priority argument.
If you try to start a thread that is already running, this function
will wait until the the thread has finished and then restart the
thread.
See also Priority.
void QThread::terminate ()
This function terminates the execution of the thread. The thread may or
may not be terminated immediately, depending on the operating system's
scheduling policies. Use QThread::wait() after terminate() for
synchronous termination.
When the thread is terminated, all threads waiting for the the thread
to finish will be woken up.
Warning: This function is dangerous, and its use is discouraged. The
thread can be terminated at any point in its code path. Threads can be
terminated while modifying data. There is no chance for the thread to
cleanup after itself, unlock any held mutexes, etc. In short, use this
function only if absolutely necessary.
void QThread::usleep ( unsigned long usecs ) [static protected]
System independent sleep. This causes the current thread to sleep for
usecs microseconds
bool QThread::wait ( unsigned long time = ULONG_MAX )
A thread calling this function will block until either of these
conditions is met:
The thread associated with this QThread object has finished execution
(i.e. when it returns from run()). This function will return TRUE if
the thread has finished. It also returns TRUE if the thread has not
been started yet.
time milliseconds has elapsed. If time is ULONG_MAX (the default), then
the wait will never timeout (the thread must return from run()). This
function will return FALSE if the wait timed out.
This provides similar functionality to the POSIX pthread_join()
function.
SEE ALSO
http://doc.trolltech.com/qthread.html
http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2007 Trolltech ASA, http://www.trolltech.com. See the
license file included in the distribution for a complete license
statement.
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. This man page is provided as a convenience for those users
who prefer man pages, although this format is not officially supported
by Trolltech.
If you find errors in this manual page, please report them to qt-
bugs@trolltech.com. Please include the name of the manual page
(qthread.3qt) and the Qt version (3.3.8).
Trolltech AS 2 February 2007 QThread(3qt)
