c++ - Qt : get mouse pressed event even if a button is pressed

Question

我需要简单地检测每时每刻在我的 Qt5/C++ 应用程序中何时按下或释放右键。

到目前为止，我已经编写了这些函数:

void test::mousePressEvent(QMouseEvent *ev){
    if(ev->buttons() == Qt::LeftButton){
        qDebug() << "Left pressed";
        ui->forceBar->setValue( 100 );
    }

}

void test::mouseReleaseEvent(QMouseEvent *ev){
    if(ev->button() == Qt::LeftButton){
        ui->forceBar->setValue( 50 );
        qDebug() << "Left released";
    }

只有当点击不是在 pushbuttontest 上时，它们才能正常工作。问题是，如果点击发生在按钮上，我不会收到事件。

Answer 1

您必须从 QPushButton 派生并覆盖这些事件处理程序。

class MyButton : public QPushButton
{
   protected:
       virtual void mousePressEvent(QMouseEvent* event);
       virtual void mouseReleaseEvent(QMouseEvent* event);
};


void MyButton::mousePressEvent(QMouseEvent *ev){
    if(ev->buttons() == Qt::LeftButton){
        qDebug() << "Left pressed";
        ui->forceBar->setValue( 100 );
    }

}

void MyButton::mouseReleaseEvent(QMouseEvent *ev){
    if(ev->button() == Qt::LeftButton){
        ui->forceBar->setValue( 50 );
        qDebug() << "Left released";
    }

然后，将此按钮用作pushbuttontest:

QPushButton* pushbuttontest = new MyButton();

或者，如果您想为许多小部件使用一个通用的事件处理程序，您可以使用事件过滤器:

class test : public QWidget // the widget in which you want to capture all events
{
public:
   bool eventFilter(QObject *watched, QEvent *e);
private:
   QPushButton* pushbuttontest;
   QLabel *myLabel;
};

bool test::eventFilter(QObject *watched, QEvent *e)
{
  if (e->type() == QEvent::MouseButtonPress)) 
   {    
      QMouseEvent* ev = (QMouseEvent*)e;
      if(ev->buttons() == Qt::LeftButton){
        qDebug() << "Left pressed";
        ui->forceBar->setValue( 100 );
    }
  }
else if (e->type() == QEvent::MouseButtonRelease)
  {
      QMouseEvent* ev = (QMouseEvent*)e;
      if(ev->buttons() == Qt::LeftButton){
        qDebug() << "Left released";
        ui->forceBar->setValue( 100 );
    }
  }
   return false;// return true if you are finished handling the event. So, the default event handler will not be called.
}

然后，将 eventFilter 安装到您想要的小部件:

pushbuttontest = new QPushButton();
pushbuttontest->instalEventFilter(this); // this is the test class object which has our event filter code.
myLabel = new QLabel();
myLabel->installEventFilter(this);

等等

请注意，我没有编译这段代码。它可能不会立即生效。

更多信息:http://qt-project.org/doc/qt-4.8/eventsandfilters.html