我需要prevent应用即时通讯做退出，如果有人推Android设备上的返回键，以便我可以发送一个消息询问用户是否希望离开应用程序或没有，我发现，使用：

I need to prevent the app im doing to exit if someone pushes the back key on an Android device so I can send a messagebox to ask if the user wants to leave the app or not, I found that using:

@Override
void MainWindow::onBackPressed()
{
    ...
}

我能处理该事件，我想在我的necessitas项目，并没有奏效。可以qtkeyevent处理呢？或者是有另一种方式来做到这一点？

I could handle that event, I tried it on my necessitas project and it didn't work. Can qtkeyevent handle this? or is there another way to do it?

我就用这个堵塞：

@Override
public boolean onKeyDown(int keyCode, KeyEvent event)
{
  if ( (keyCode == KeyEvent.KEYCODE_BACK) )
   {
     //moveTaskToBack(true); 
     return true;
   }
if (QtApplication.m_delegateObject != null && 
        QtApplication.onKeyDown != null)
   return (Boolean) 
QtApplication.invokeDelegateMethod(QtApplication.onKeyDown, keyCode, event);
   else
   return super.onKeyDown(keyCode, event);
}

现在我需要捕捉Qt的事件，所以我的发送邮件

Now I need to capture the event on Qt so I an send a message

推荐答案

下面是如何解决这个问题：

Here is how to solve it:

@Override
    public boolean onKeyDown(int keyCode, KeyEvent event)
    {
        int newKeyCode = keyCode;
        if ( (keyCode == KeyEvent.KEYCODE_BACK) )
        {
           newKeyCode = KeyEvent.KEYCODE_MEDIA_PREVIOUS;
        }
        if (QtApplication.m_delegateObject != null &&
QtApplication.onKeyDown != null)
            return (Boolean)
QtApplication.invokeDelegateMethod(QtApplication.onKeyDown, newKeyCode,
event);
        else
            return super.onKeyDown(newKeyCode, event);
    }
    public boolean super_onKeyDown(int keyCode, KeyEvent event)
    {
        return super.onKeyDown(keyCode, event);
    }

//---------------------------------------------------------------------------

    @Override
    public boolean onKeyMultiple(int keyCode, int repeatCount, KeyEvent
event)
    {
        int newKeyCode = keyCode;
        if ( (keyCode == KeyEvent.KEYCODE_BACK) )
        {
            newKeyCode = KeyEvent.KEYCODE_MEDIA_PREVIOUS;
        }
        if (QtApplication.m_delegateObject != null &&
QtApplication.onKeyMultiple != null)
            return (Boolean)
QtApplication.invokeDelegateMethod(QtApplication.onKeyMultiple ,newKeyCode,
repeatCount, event);
        else
            return super.onKeyMultiple(newKeyCode, repeatCount, event);
    }
    public boolean super_onKeyMultiple(int keyCode, int repeatCount,
KeyEvent event)
    {
        return super.onKeyMultiple(keyCode, repeatCount, event);
    }

//---------------------------------------------------------------------------

    @Override
    public boolean onKeyUp(int keyCode, KeyEvent event)
    {
        int newKeyCode = keyCode;
        if ( (keyCode == KeyEvent.KEYCODE_BACK) )
        {
            newKeyCode = KeyEvent.KEYCODE_MEDIA_PREVIOUS;
        }
        if (QtApplication.m_delegateObject != null  &&
QtApplication.onKeyDown != null)
            return (Boolean)
QtApplication.invokeDelegateMethod(QtApplication.onKeyUp, newKeyCode,
event);
        else
            return super.onKeyUp(newKeyCode, event);
    }
    public boolean super_onKeyUp(int keyCode, KeyEvent event)
    {
        return super.onKeyUp(keyCode, event);
    } 

，然后在Qt的：

and then in Qt:

void MainWindow::keyPressEvent(QKeyEvent *k)
{
    if( k->key() == Qt::Key_MediaPrevious )
    {
        int ret = messageBox( QMessageBox::Yes | QMessageBox::No, "¿Desea salir de la aplicación?", QMessageBox::Question);

        switch(ret)
        {
        case QMessageBox::Yes:
            this->close();
            break;

        case QMessageBox::No:
            break;
        }
    }
}

由于Koying是张贴在这里这个解决方案的http://groups.google.com/group/android-qt/browse_thread/thread/676c24e94bb9a200?pli=1