正确使用Qt QProcess

Question

我正在考虑多次使用QProcess来调用一个命令行应用程序(gpio)。每次用户点击一个按钮，就会发出一个命令。

应用程序的输出将被监控并重定向至screeen。代码如下所示。

void Gpio::command(QString argument)
{
//    if(process)
//        delete process;
    process = new QProcess(this);
    connect(process, SIGNAL(started()), this, SLOT(onStart()));
    connect(process, SIGNAL(finished(int,QProcess::ExitStatus)), this, SLOT(onFinish(int,QProcess::ExitStatus)));
    connect(process, SIGNAL(readyReadStandardOutput()), this, SLOT(readGpio()));
    QString program("gpio");
    QStringList list = argument.split(" ");
    process->start(program, list);
}

问:我应该使用delete process吗？这样做我得到了：

QProcess: Destroyed while process is still running.

监控exitCode和exitStatus，我发现它们都是0。

这个问题更多的是关于QProcess的正确使用，而"QProcess and shell : Destroyed while process is still running"关注的是特定的错误。

Answer 1

因为您不想同时运行多个进程(根据注释)，所以不需要多次创建/删除QProcess。

gpio.h

QProcess*   m_gpioProcess;

gpio.cpp文件

Gpio::Gpio(.....),
   .....(),
   m_gpioProcess(new QProcess(this))
{
   m_gpioProcess->setProgram("gpio");

   connect(m_gpioProcess, SIGNAL(started()), this, SLOT(onStart()));
   connect(m_gpioProcess, SIGNAL(finished(int,QProcess::ExitStatus)), this, SLOT(onFinish(int,QProcess::ExitStatus)));
   connect(m_gpioProcess, SIGNAL(readyReadStandardOutput()), this, SLOT(readGpio()));
}

void Gpio::command(const QString& args)
{
  if (m_gpioProcess->state() != QProcess::NotRunning) {
    qDebug() << "Process already running, ignoring the request";
    return;
  }

  m_gpioProcess->setArguments(args.split(" "));
  m_gpioProcess->start();
  if (m_gpioProcess->waitForStarted()) {
    qDebug() << "Process started with arguments:" << m_gpioProcess->arguments();
  }
}

如果您希望防止用户多次单击该按钮，请考虑根据m_gpioProcess状态启用/禁用该按钮。

对于Qt 4.8，只需删除此行

m_gpioProcess->setProgram("gpio");

这一行

m_gpioProcess->setArguments(args.split(" "));

并更改这一行

m_gpioProcess->start();

至

m_gpioProcess->start("gpio", args.split(" "));

Answer 2

看起来在给start打电话之后我忘记了process->waitForFinished();。这似乎解决了问题。

Answer 3

添加以下代码可能会有帮助：

process->close();