eventFilter(QObject *obj, QEvent *e) 没有检测到正确的对象

Question

我希望我的程序在我的鼠标位于 labelname（一个 QLabel）时打印 "mouse on label name"，而在我的鼠标不在时打印 "mouse not on label name"位于 labelname.

即使我将鼠标放在 labelname 上，我的程序也会打印 "mouse not on label name"。

我怎么知道鼠标不在 labelname 上？

bool Dialog::eventFilter(QObject *obj, QEvent *e)
{
    if(qobject_cast<QLabel*>(obj) == ui->labelname) {
    cout << “mouse on label name” << endl;
    }else if(qobject_cast<QLabel*>(obj) != ui->labelname) { 
    cout << “mouse not on label name” << endl;
    }
    return false;
}

Answer 1

确保您正在安装指示鼠标已进入或离开小部件的 event filter correctly. Also, if you want to track mouse position you have to enable mouseTracking, otherwise the move events won't be triggered (though QEvent::Enter and QEvent::Leave will, which are the ones。

这里是一个简单的操作示例：

MyWidget::MyWidget(QWidget *parent)
  : QWidget(parent)
{
  m_label = new QLabel("Hello world!");
  m_label->setObjectName("m_label");
  m_label->installEventFilter(this);
  m_label->setMouseTracking(true);

  auto hlayout = new QVBoxLayout();
  hlayout->addWidget(m_label);
  setLayout(hlayout);
}

bool MyWidget::eventFilter(QObject* sender, QEvent* event)
{
  if (sender == m_label) {
    qDebug() << sender->objectName() << event->type();

    if (event->type() == QEvent::Enter) {
      qDebug() << "mouse on label name";
    } else if (event->type() == QEvent::Leave) {
      qDebug() << "mouse not on label name";
    }
  }

  return QWidget::eventFilter(sender, event);
}

GitHub 中提供了完整的工作示例。