如何在使用Qt时阻止android中的后退键

How to block the back key in android when using Qt

本文关键字：android Qt      更新时间：2023-10-16

如果有人按下安卓设备上的后退键，我需要阻止应用程序退出，这样我就可以发送一个消息框询问用户是否想离开应用程序，我发现使用：

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

我可以处理那个事件，我在必要的项目中尝试过，但没有成功。qtkeyevent能处理这个问题吗？或者还有别的办法吗？

我用这个阻止它：

@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);
}

现在我需要在Qt上捕获事件，这样我就可以发送一条消息

以下是解决方法：

@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:中

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;
        }
    }
}

感谢Koying在这里发布这个解决方案http://groups.google.com/group/android-qt/browse_thread/thread/676c24e94bb9a200?pli=1

您可以为"活动"编写onKeyListener，检查键代码，如果它们是您想要的，使用它们。至少，在Java。当然，C++的可能性并没有减少。

不太确定这是否适用于您的情况，但在Android中，通常情况下，在每个感兴趣的Activity中，您都会使用以下内容来覆盖后退按钮按下：

@Override
public void onBackPressed()
{
    // Make sure to NOT call super!
    ...
}
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