QT中的事件过滤器

示例

class MainWindow : public QMainWindow {
public:
  MainWindow();

protected:
  bool eventFilter(QObject *obj, QEvent *ev) override;

private:
  QTextEdit *textEdit;
};

MainWindow::MainWindow() {
  textEdit = new QTextEdit;
  setCentralWidget(textEdit);

  textEdit->installEventFilter(this);
}

bool MainWindow::eventFilter(QObject *obj, QEvent *event) {
  if (obj == textEdit) {
    if (event->type() == QEvent::KeyPress) {
      QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);
      qDebug() << "Ate key press" << keyEvent->key();
      return true;
    }
    else {
      return false;
    }
  }
  else {
    // pass the event on to the parent class
    return QMainWindow::eventFilter(obj, event);
  }
}

注册事件过滤器的参数是需要重写eventFilter的那个类的指针，未处理的事件传递给基类。

Notice in the example above that unhandled events are passed to the base class’s eventFilter() function, since the base class might have reimplemented eventFilter() for its own internal purposes.

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