QT笔记——QProcess学习

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我们常常想通过某一个类，来启动一个外部进程

本文将讲解如何通过QProcess来进行启动外部进程

一：了解QProcess

QProcess是Qt框架提供的一个类，用于在应用程序中执行外部进程。它提供了一系列函数来启动、控制和与外部进程进行交互

[static] bool QProcess::startDetached(const QString &program, const QStringList &arguments, const QString &workingDirectory = QString(), qint64 *pid = nullptr) 

(1.2)一体式：当主程序退出时,被主程序调用起来的进程也退出

void QProcess::start(const QString &program, const QStringList &arguments, QIODevice::OpenMode mode = ReadWrite) 

2：常用的阻塞函数

// 主进程阻塞，直到外部程序启动完毕, waitForStarted() // 主进程阻塞，直到外部程序执行完毕 waitForFinished() 

3:被调用进程接受数据

QStringList list = QCoreApplication::arguments(); //为什么试3个呢，我明明参数是传的两个 因为第一个参数是我们传的exe启动 全路径 C:\Users\admin\Desktop\a.exe if (list.size() == 3) { 
    QString exeFileName= list.at(0); QString oneStr = list.at(1); QString twoStr= list.at(2); } 

QFile file; file.open(1, QFile::WriteOnly); file.write("finished"); file.close(); 

(4.2)使用输出流 被 主进程捕获

 cout << "it's message" << endl; 

//启动完毕 connect(process, &QProcess::started, this, [=]() { 
    }); //捕获到消息时 connect(process, &QProcess::readyReadStandardOutput, this, [=]() { 
    }); //完成 connect(process, QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished), this, [=](int exitCode, QProcess::ExitStatus exitStatus) { 
    }); //状态改变 connect(process, &QProcess::stateChanged, this, [=](QProcess::ProcessState state) { 
    }); 

二：使用QPrecess

1：startDetached 启动进程

void QTcpSeverTest::on_btn1_clicked() { 
    QProcess* process = new QProcess(this); QString str = QApplication::applicationDirPath() + "/QTcpClientTest.exe"; QStringList list; list.append("123"); list.append("456"); //分离式 启动外部进程 process->startDetached(str, list); //无效 connect(process, &QProcess::started, this, [=]() { 
    qDebug() << "started"; }); //无效 connect(process, &QProcess::readyReadStandardOutput, this, [=]() { 
    QString qstr(process->readAllStandardOutput()); qDebug() << "startDetached:" << qstr; }); connect(process, QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished), this, [=](int exitCode, QProcess::ExitStatus exitStatus) { 
    QString result = process->readAll(); qDebug() << "result:" << result; }); //无效 connect(process, &QProcess::stateChanged, this, [=](QProcess::ProcessState state) { 
    qDebug() << "show state:"; switch (state) { 
    case QProcess::NotRunning: qDebug() << "Not Running"; break; case QProcess::Starting: qDebug() << "Starting"; break; case QProcess::Running: qDebug() << "Running"; break; default: qDebug() << "otherState"; break; } }); } 

2：start启动进程

 QProcess* process = new QProcess(this); QString str = QApplication::applicationDirPath() + "/QTcpClientTest.exe"; QStringList list; list.append("bbbbb"); list.append("aaaaa"); //启动完毕 connect(process, &QProcess::started, this, [=]() { 
    qDebug() << "started:" ; }); //捕获到消息时 connect(process, &QProcess::readyReadStandardOutput, this, [=]() { 
    QString qstr(process->readAllStandardOutput()); qDebug() << "readyReadStandardOutput:" << qstr; }); //完成 connect(process, QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished), this, [=](int exitCode, QProcess::ExitStatus exitStatus) { 
    if (exitStatus == QProcess::NormalExit) { 
    qDebug() << "Process finished with exit code:" << exitCode; } else { 
    qDebug() << "Process crashed!"; } }); //状态改变 connect(process, &QProcess::stateChanged, this, [=](QProcess::ProcessState state) { 
    qDebug() << "show state:"; switch (state) { 
    case QProcess::NotRunning: qDebug() << "Not Running"; break; case QProcess::Starting: qDebug() << "Starting"; break; case QProcess::Running: qDebug() << "Running"; break; default: qDebug() << "otherState"; break; } }); //一体式 启动外部进程 process->start(str, list); 

3：execute()启动进程

 QProcess* process = new QProcess(this); QString str = QApplication::applicationDirPath() + "/QTcpClientTest.exe"; QStringList list; list.append("bbbbb"); list.append("aaaaa"); //无效 connect(process, &QProcess::started, this, [=]() { 
    qDebug() << "started:"; }); //无效 connect(process, &QProcess::readyReadStandardOutput, this, [=]() { 
    QString qstr(process->readAllStandardOutput()); qDebug() << "readyReadStandardOutput:" << qstr; }); //无效 connect(process, QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished), this, [=](int exitCode, QProcess::ExitStatus exitStatus) { 
    QString result = process->readAll(); qDebug() << "result:" << result; }); //无效 connect(process, &QProcess::stateChanged, this, [=](QProcess::ProcessState state) { 
    qDebug() << "show state:"; switch (state) { 
    case QProcess::NotRunning: qDebug() << "Not Running"; break; case QProcess::Starting: qDebug() << "Starting"; break; case QProcess::Running: qDebug() << "Running"; break; default: qDebug() << "otherState"; break; } }); //如果进程 QTcpClientTest 不关闭 或者完成 ， 则此进程一直卡住 int exitCode = QProcess::execute(str, list); if (exitCode != 0) { 
    qDebug() << "外部程序执行失败"; } //接受进程捕获到输出的消息 QByteArray output = process->readAllStandardOutput(); QString msg = QString::fromLocal8Bit(output); qDebug() << msg; 

打印的信息为：QIODevice::read (QProcess): device not open，说明execute没有打开设备，接受不到消息

4：start() + waitForFinished()启动进程

 QProcess* process = new QProcess(this); QString str = QApplication::applicationDirPath() + "/QTcpClientTest.exe"; QStringList list; list.append("bbbbb"); list.append("aaaaa"); //启动进程 process->start(str,list); // 等待进程完成 process->waitForFinished(); //接受进程捕获到输出的消息 QByteArray output = process->readAllStandardOutput(); QString msg = QString::fromLocal8Bit(output); qDebug() << msg;