QThread 认知

Posted 2020-12-14 huanyinglvtuan

QThread 认知

线程启动

void start(Priority priority = InheritPriority)

调用后会执行run()函数，但在run()函数执行前会发射信号started()，操作系统将根据优先级参数调度线程。如果线程已经在运行，那么这个函数什么也不做。优先级参数的效果取决于操作系统的调度策略。特别是那些不支持线程优先级的系统优先级将会被忽略（例如在Linux中，更多细节请参考http://linux.die.net/man/2/sched_setscheduler）

下面来看下优先级中的各个枚举值：

Constant	Value	Description
QThread::IdlePriority	0	没有其它线程运行时才调度.
QThread::LowestPriority	1	比LowPriority调度频率低.
QThread::LowPriority	2	比NormalPriority调度频率低.
QThread::NormalPriority	3	操作系统默认的默认优先级.
QThread::HighPriority	4	比NormalPriority调度频繁.
QThread::HighestPriority	5	比HighPriority调度频繁.
QThread::TimeCriticalPriority	6	尽可能频繁的调度.
QThread::InheritPriority	7	使用和创建线程同样的优先级. 这是默认值.

案例

#ifndef ASENDTUNNEL_H
#define ASENDTUNNEL_H

#include <QObject>
#include <QTimer>
#include <QThread>

class AThreadTestObj : public QObject
{
    Q_OBJECT
public:
    explicit AThreadTestObj(QObject *parent = 0);

    void printInfo();
signals:

public slots:
    void sltInit();
    void sltDeinit();
    void sltTimeOut();

private:
    QTimer *m_ptimer;
    QThread m_thread;
};

#endif // ASENDTUNNEL_H

#include "asendtunnel.h"
#include <QDebug>

AThreadTestObj::AThreadTestObj(QObject *parent) : QObject(parent)
{
    moveToThread(&m_thread);
    connect(&m_thread, &QThread::started, this, &AThreadTestObj::sltInit);
    connect(&m_thread, &QThread::finished, this, &AThreadTestObj::sltDeinit);
    m_thread.start(QThread::TimeCriticalPriority);
}

void AThreadTestObj::printInfo()
{
    qDebug() << "printInfo:" << QThread::currentThreadId();
}

void AThreadTestObj::sltInit()
{
    m_ptimer = new QTimer();
    connect(m_ptimer, &QTimer::timeout, this, &AThreadTestObj::sltTimeOut);
    m_ptimer->start(5000);
    qDebug() << "sltInit:" << QThread::currentThreadId();
}

void AThreadTestObj::sltDeinit()
{
    delete m_ptimer;
}

void AThreadTestObj::sltTimeOut()
{
    qDebug() << "sltTimeOut:" << QThread::currentThreadId();
}

#include <QCoreApplication>
#include "asendtunnel.h"

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    AThreadTestObj m_sendTunnel;
    m_sendTunnel.printInfo();
    return a.exec();
}

结果：

printInfo: 0x6f34
sltInit: 0x68b8
sltTimeOut: 0x68b8
sltTimeOut: 0x68b8

总结：外面调用接口执行的是主线程,子线程执行的内容通过定时器，因为定时器是在子线程创建的,另外从执行的顺序来看，最好的主线程在创建对象后最后有个等待再去执行其他接口

案例:加了等待初始化接口

#ifndef ASENDTUNNEL_H
#define ASENDTUNNEL_H

#include <QObject>
#include <QTimer>
#include <QThread>
#include <QAtomicInt>

class AThreadTestObj : public QObject
{
    Q_OBJECT
public:
    explicit AThreadTestObj(QObject *parent = 0);
    ~AThreadTestObj();
    bool waitForStarted();
    void waitForStoped();
    void printInfo();
signals:

public slots:
    void sltInit();
    void sltDeinit();
    void sltTimeOut();

private:
    QTimer *m_ptimer;
    QThread m_thread;
    QAtomicInt m_iInitSuccess{0};
};

#endif // ASENDTUNNEL_H

#include "asendtunnel.h"
#include <QDebug>

AThreadTestObj::AThreadTestObj(QObject *parent) : QObject(parent),m_ptimer(nullptr)
{
    moveToThread(&m_thread);
    connect(&m_thread, &QThread::started, this, &AThreadTestObj::sltInit);
    connect(&m_thread, &QThread::finished, this, &AThreadTestObj::sltDeinit);
    if(!waitForStarted())
        throw std::runtime_error("waitForStarted error");

}

AThreadTestObj::~AThreadTestObj()
{
    waitForStoped();
}

bool AThreadTestObj::waitForStarted()
{
    m_thread.start(QThread::TimeCriticalPriority);
    int i =0;
    while(m_iInitSuccess.load() !=1)
    {
       QThread::msleep(100);
       if(m_iInitSuccess.load() == -1)
       {
           waitForStoped();
           qDebug()<<"AThreadTestObj start failed";
           return false;
       }

       if(300 == ++i)
       {
           waitForStoped();
           qDebug()<<"AThreadTestObj start failed due to timeout";
           return false;
       }
    }
    qDebug()<<"AThreadTestObj start Succeed wait times:"<<i;
    return true;
}

void AThreadTestObj::waitForStoped()
{
    m_thread.quit();
    m_thread.requestInterruption();
    m_thread.wait();
    qDebug() << "AThreadTestObj::waitForStoped";
}

void AThreadTestObj::printInfo()
{
    qDebug() << "printInfo:" << QThread::currentThreadId();
}

void AThreadTestObj::sltInit()
{
    m_ptimer = new QTimer();
    if(m_ptimer == nullptr)
    {
        m_iInitSuccess.store(-1);
        return;
    }
    connect(m_ptimer, &QTimer::timeout, this, &AThreadTestObj::sltTimeOut);
    m_ptimer->start(5000);
    qDebug() << "sltInit:" << QThread::currentThreadId();
    m_iInitSuccess.store(1);
}

void AThreadTestObj::sltDeinit()
{
    delete m_ptimer;
}

void AThreadTestObj::sltTimeOut()
{
    qDebug() << "sltTimeOut:" << QThread::currentThreadId();
}

#include <QCoreApplication>
#include <QDebug>
#include "asendtunnel.h"

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    try
    {
        AThreadTestObj m_sendTunnel;
        m_sendTunnel.printInfo();
        return a.exec();
    }
    catch(std::runtime_error &e)
    {
        qDebug() << e.what();
    }
    catch(...)
    {
        qDebug() << "error";
    }

    return a.exec();
}

sltInit: 0x73f0
AThreadTestObj start Succeed wait times: 1
printInfo: 0x6fe0
sltTimeOut: 0x73f0
sltTimeOut: 0x73f0