QT Create thread

Http://www.cnblogs.com/xinxue/p/6840315.html

The qtconcurrent of Qt

This article takes the Qtconcurrent::run () function in Qt as an example to show how to run a function in a separate thread.

1 Qtconcurrent::run ()

Qtconcurrent is a namespace that provides a high-level function interface (APIS) that allows the program to automatically adjust the number of threads that are running based on the actual number of CPU cores in the current computer.

The following is the self-contained routine in Qt runfunction, which corresponds to the installation directory D:\Qt\Qt5.8.0\Examples\Qt-5.8\qtconcurrent\runfucntion

1.1. Pro Project Files

Using the Qtconcurrent module, you need to add it in. Pro: QT + = Concurrent

QT + = Concurrent Widgetsconfig + = consoleconfig-app_bundlesources + = Main.cpp

1.2 main.cpp

1 #include <QApplication> 2 #include <QDebug> 3 #include <QThread> 4  5 #include <QString> 6 #i Nclude <QtConcurrent> 7  8 void func (QString name) 9 {     qdebug () << "Hello" << name << "fr Om "<< qthread::currentthread ();}12 int main (int argc, char **argv) (     qapplication, argc), 16     qfuture<void> fut1 = Qtconcurrent::run (func, QString ("Thread 1"));     qfuture<void> fut2 = Qtconcurrent::run (func, QString ("Thread 2");     fut1.waitforfinished ();     fut2.waitforfinished (); 22}

As you can see, using the Qtconcurrent::run () function, the Func () is run in two different threads, with the result of the output as follows:

Hello "Thread 2" from Qthread (0x3597f0, name = "Thread (Pooled)") Hello "Thread 1" from Qthread (0x337720, name = "Thread" (p ooled) ")

Here's a detailed explanation of using Qtconcurrent::run (), reading 2 and 3, and then looking at the runfunction routines above, it's very easy to understand.

2 Common functions

2.1 To run a function in a thread

extern void Func (); qfuture<void> future = Qtconcurrent::run (func);

If you want to specify a thread pool for it, you can pass a pointer to the thread pool as the first argument in

extern void Func (); Qthreadpool Pool; qfuture<void> future = Qtconcurrent::run (&pool, func);

2.2 Passing parameters to the function

Parameters that need to be passed, followed by the function name, followed by

extern void funcwitharguments (int arg1, const QString &string); int integer = ...; QString string = ...; qfuture<void> future = Qtconcurrent::run (funcwitharguments,integer,string);

2.3 Get the calculation result of the function

extern QString Func (const qbytearray &input); Qbytearray Byte_array = ...; qfuture<qstring> future = Qtconcurrent::run (func, Byte_array); QString result = Future.result ();

3 member functions

To run a member function in a class in a thread, you can pass a reference or pointer to the instance of the class as the first argument to the Qtconcurrent::run.

A constant member function generally passes a constant reference (const reference), whereas a generic member function generally passes a pointer (pointer)

3.1 Constant member functions

In a separate thread, call Qbytearray's constant member function split (), and the argument passed to the run () function is ByteArray

  Qbytearray ByteArray = "Hello World";  qfuture<qlist<qbytearray> > Future = Qtconcurrent::run (ByteArray, &qbytearray::split, ', ');  ...  qlist<qbytearray> result = Future.result ();

3.2 A very-mass member function

In a separate thread, the Qimage member function called Invertpixels (), which is passed to the run () function, is &image

  Qimage image = ...;  qfuture<void> future = Qtconcurrent::run (&image, &qimage::invertpixels, Qimage::invertrgba);  ...  Future.waitforfinished ();
  At this point, the pixels in ' image ' has been inverted

QT Create thread