Qt文档阅读笔记-QFuture官方解析及实例

怼烎@ 2022-12-07 04:25 137阅读 0赞

QFurture是异步进行的，可以开1个或多个线程。返回值可以是任意类型的。当调用result(), resultAt(), results()返回值无效时QFuture将会等待result返回正常为止。可以使用isResultReadAt()函数去判断是否有数据。QFuture返回值可以是多个，使用resultCount()函数可以得到其数量。

还有很多函数就不一一介绍了。直接在代码中演示吧！

下面是一个官方例子：

runfunction.pro

QT += concurrent widgets
    CONFIG += cmdline
    
    SOURCES += main.cpp
    
    target.path = $$[QT_INSTALL_EXAMPLES]/qtconcurrent/runfunction
    INSTALLS += target

main.cpp

#include <QDebug>
    #include <QThread>
    #include <QString>
    #include <qtconcurrentrun.h>
    #include <QApplication>
    
    using namespace QtConcurrent;
    
    void hello(QString name)
    {
        qDebug() << "Hello" << name << "from" << QThread::currentThread();
    }
    
    int main(int argc, char **argv)
    {
        QApplication app(argc, argv);
        QFuture<void> f1 = run(hello, QString("Alice"));
        QFuture<void> f2 = run(hello, QString("Bob"));
        f1.waitForFinished();
        f2.waitForFinished();
    }

程序运行截图如下：

![20200915084745161.png][]

下面是处理大量数据的例子：

源码如下：

FutureDemo.pro

QT -= gui
    QT += concurrent
    
    CONFIG += c++11 console
    CONFIG -= app_bundle
    
    # The following define makes your compiler emit warnings if you use
    # any Qt feature that has been marked deprecated (the exact warnings
    # depend on your compiler). Please consult the documentation of the
    # deprecated API in order to know how to port your code away from it.
    DEFINES += QT_DEPRECATED_WARNINGS
    
    # You can also make your code fail to compile if it uses deprecated APIs.
    # In order to do so, uncomment the following line.
    # You can also select to disable deprecated APIs only up to a certain version of Qt.
    #DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0
    
    SOURCES += \
            main.cpp
    
    # Default rules for deployment.
    qnx: target.path = /tmp/$${TARGET}/bin
    else: unix:!android: target.path = /opt/$${TARGET}/bin
    !isEmpty(target.path): INSTALLS += target

main.cpp

#include <QCoreApplication>
    #include <QtConcurrent>
    #include <QTimer>
    #include <QTime>
    #include <QEventLoop>
    #include <QVector>
    #include <QMapIterator>
    #include <QString>
    #include <QDebug>
    #include <QMap>
    
    using namespace QtConcurrent;
    
    
    QVector<int> MyTest(QVector<int> vec){
    
        qDebug() << "deal with vec !  " << QThread::currentThread();
    
        QVector<int> ret;
    
        for(int i = 0; i < vec.size(); i++){
    
            ret << vec[i] - vec[i];
        }
        qDebug() << "deal with vec !  finished" << QThread::currentThread();
    
        return ret;
    }
    
    
    int main(int argc, char *argv[])
    {
        QCoreApplication a(argc, argv);
    
        qsrand(QTime(0, 0, 0).secsTo(QTime::currentTime()));
    
        QVector<int> oriData;
        for(int i = 0; i < 1000000; i++){
    
            oriData.append(qrand() % 50000);
        }
    
        qDebug() << "随机数生成完成！";
    
        QVector<int> overData;
        QList<QFuture<QVector<int>>> list;
    
        for(int i = 0; i < 1000000; i+= 10000){
    
            QFuture<QVector<int>> future = run(MyTest, oriData.mid(i, 10000));
            list.append(future);
        }
    
        QEventLoop loop;
        QTimer::singleShot(2 * 1000, &loop, &QEventLoop::quit);
        loop.exec();
    
    
        for(int i = 0; i < list.size(); i++){
    
            list[i].waitForFinished();
            overData.append(list[i]);
        }
    
    
        qDebug() << "over";
        return a.exec();
    }

运行截图如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxNzg0NDI3NjE_size_16_color_FFFFFF_t_70][]

变量

![20200915084958193.png][]

[20200915084745161.png]: /images/20221123/5a688b0c0bb74f0ebac156b2de61fa00.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxNzg0NDI3NjE_size_16_color_FFFFFF_t_70]: /images/20221123/0523965cf2e146209670f858f1c00aeb.png
[20200915084958193.png]: /images/20221123/85552bd01b7b435c8898359bdade0858.png