QThread 采用moveToThread方式實現多線程。 線程本身、connect關聯的槽函數、connect關聯的lambda對象分別運行在哪個線程中。

Qt如何實現多線程：https://www.cnblogs.com/azbane/p/11372531.html

September 5，2019

先拋出幾個問題，用問題來引導思維導向：

1、繼承的QObject子類，和QThread對象，是在哪個線程創建的？（即：QObject子類對象和QThread對象的依附線程是哪個？）

2、QThread在哪個線程運行？

3、QObject::moveToThread( QThread )后，QThread 的信號(started/finished)關聯的QObject子類對象的函數（槽函數）哪個線程運行？

4、QObject::moveToThread( QThread ) 后，QThread的信號(started/finished)關聯的依附線程對象的槽函數在哪個線程運行？

5、信號和槽的新版本，用lambda表達式處理信號的情況（QThread的信號(started/finished)關聯的lambda），lambda對象運行在哪個對象？

 

看起來很復雜，其實並不可怕：想知道對象在哪個線程運行，有兩種方式可用

1：QThread::currentThreadId()  返回16進制的線程ID (#include<QThread>)

2：std::this_thread::get_id() 返回10進制的線程ID  （#include<iostream> #include <QThread>）

 

先給答案，再上例子說明， 最后給出遇到的錯誤情況。

上面跑出的5個問題的答案：

假定QObject子類對象和QThread對象都是在線程A中創建。

1、線程A。  調用std::this_thread::get_id

2、線程A。  調用QThread::currentThreadId， 需要由16進制轉成10進制，再對比。

3、線程B。  假定線程id = B 。調用std::this_thread::get_id

4、線程A。  調用std::this_thread::get_id

5、線程B。  調用std::this_thread::get_id

 

例子主要信息說明：

類ShapeLayout:

　　　　　　有兩個指針數據成員：GenerateGridFileWork * m_generateGridFileWork;   QThread * m_generateGridFileWorkThread;

　　　　　　有一個函數成員：MakeGrid， 函數里面創建兩個指針數據成員。

                      m_generateGridFileWork->moveToThread(m_generateGridFileWorkThread);

　　　　　　GenerateGridFileWork::slotsWork
　　　　　　QThread::signals - started / finished

ShapeLayout.h
-----------------------------------------------------------
class ShapeLayout :  public QObject
{
  Q_OBJECT

public:
    void makeGrid();

public slots:
  void slotsThreadFininshed(); 

private:
    GenerateGridFileWork * m_GenerateGridFileWork = nullptr;
    QThread * m_GenerateGridFileWorkThread = nullptr;   
}

ShapeLayout.cpp 
-----------------------------------------------------------
void ShapeLayout::makeGrid()
{
    std::cout<<"ShapeLayout thread id is "<<std::this_thread::get_id()<<std::cout;  //問題-1
    m_GenerateGridFileWork  = new GenerateGridFileWork ;
    m_GenerateGridFileWorkThread  =  new QThread;

    m_GenerateGridFileWork->moveToThread(m_GenerateGridFileWorkThread);

    QObject::connect(m_GenerateGridFileWorkThread, &QThread::started, m_GenerateGridFileWork  , &GenerateGridFileWork::slotsWork);
    
    QObject::connect(m_GenerateGridFileWork, &GenerateGridFileWork::signalsWorkFinished, m_GenerateGridFileWorkThread, &QThread::quit);

    QObject::connect(m_GenerateGridFileWorkThread, &QThread::finished, this, &ShapeLayout::slotsThreadFininshed);
     
    QObject::connect(m_GenerateGridFileWorkThread, &QThread::started, []{
     std::cout<<"connect thread-started signals lambda object  thread id is"<<std::this_thread::get_id()<<std::cout; //問題-5
});

    QObject::connect(m_GenerateGridFileWorkThread, &QThread::finished, []{
    std::cout<<"connect thread-finishedsignals lambda object  thread id is"<<std::this_thread::get_id()<<std::cout;//問題-5

});

    std::cout<<"QThread thread id is "<<m_generateGridFileWorkThread->currentThreadId()<<std::cout; //問題-2 

    m_GenerateGridFileWorkThread->start();

}

void ShapeLayout::slotsThreadFininshed()
{
　　std::cout<<"connect slots function of the ShapeLayout attributable thread id is"<<std::this_thread::get_id()<<std::cout;//問題-4
}

 

GenerateGridFileWork.h
------------------------------------------------
class GenerateGridFileWork : public QObject
{
public slots:
       void slotsWork();

signals:
       void signalsWorkFinished();
}

GenerateGridFileWork.cpp
------------------------------------------------
void GenerateGridFileWork::slotsWork()
{
      std::cout<<"connect to slots function of QObject subObject thread id is "<<std::this_thread::get_id()<<std::cout;//問題-3

      emit   signalsWorkFinished();
} 

 

 

 

調用ShapeLayout::makeGrid()；　一切都知道啦，  自己去運行一遍吧

OK perfect...

 

 September 5, 2019追加一個問題：

moveToThread的方式實現的線程，作業完成后，針對QObject的子類對象和QThread對象的釋放順序有沒有講究？