在 QObject 中更改鼠标光标 - QGraphicsItem 继承类

问题描述

当鼠标光标位于图形项目中时，我想更改鼠标光标(MyCircle 继承自 QObject 和 QGraphicsItem).如果我的类继承自 QWidget，我会重新实现 enterEvent() 和 leaveEvent() 并按如下方式使用它:

I would like to change my mouse cursor when it is in a graphics item (MyCircle inherits from QObject and QGraphicsItem).Had my class inherited from QWidget, I would have reimplemented enterEvent() and leaveEvent() and use it as follows :

MyCircle::MyCircle(QObject *parent)
    : QWidget(parent), QGraphicsItem() // But I can't
{
    rect = QRect(-100,-100,200,200);
    connect(this,SIGNAL(mouseEntered()),this,SLOT(in()));
    connect(this,SIGNAL(mouseLeft()),this,SLOT(out()));
}

void MyCircle::in()
{
    QApplication::setOverrideCursor(Qt::PointingHandCursor);
}

void MyCircle::out()
{
    QApplication::setOverrideCursor(Qt::ArrowCursor);
}

void MyCircle::enterEvent(QEvent *)
{
    emit mouseEntered();
}

void MyCircle::leaveEvent(QEvent *)
{
    emit mouseLeft();
}

不幸的是，我需要为那个圆圈设置动画(它实际上是一个按钮)，所以我需要 QObject，有没有一种简单的方法可以更改光标?

Unfortunately, I need to animate that circle (it's a button actually), so I need QObject, is there an easy way to change the cursor ?

推荐答案

你或许可以使用 悬停事件.

在你的类构造函数中确保你做...

In your class constructor make sure you do...

setAcceptHoverEvents(true);

然后覆盖 hoverEnterEvent 和hoverLeaveEvent.

virtual void hoverEnterEvent (QGraphicsSceneHoverEvent *event) override
{
  QGraphicsItem::hoverEnterEvent(event);
  QApplication::setOverrideCursor(Qt::PointingHandCursor);
}

virtual void hoverLeaveEvent (QGraphicsSceneHoverEvent *event) override
{
  QGraphicsItem::hoverLeaveEvent(event);
  QApplication::setOverrideCursor(Qt::ArrowCursor);
}

附带说明:您实际上是否同时继承了 QObject 和 QGraphicsItem?如果是这样，您可能可以通过简单地继承 QGraphicsObject.

As a side note: do you actually inherit from both QObject and QGraphicsItem? If so, you could probably achieve the same goal by simply inheriting from QGraphicsObject.

编辑 1:为了回答...

我的整个边界矩形中有指向手图标，我怎么能仅将区域缩小到我的绘图(在本例中为圆形)?

覆盖QGraphicsItem::shape 返回一个 QPainterPath 表示实际形状...

virtual QPainterPath shape () const override
{
  QPainterPath path;

  /*
   * Update path to represent the area in which you want
   * the mouse pointer to change.  This will probably be
   * based on the code in your 'paint' method.
   */
  return(path);
}

现在覆盖 QGraphicsItem::hoverMoveEvent 使用 shape 方法...

Now override QGraphicsItem::hoverMoveEvent to make use of the shape method...

virtual void hoverMoveEvent (QGraphicsSceneHoverEvent *event) override
{
  QGraphicsItem::hoverMoveEvent(event);
  if (shape().contains(event->pos())) {
    QApplication::setOverrideCursor(Qt::PointingHandCursor);
  } else {
    QApplication::setOverrideCursor(Qt::ArrowCursor);
  }
}

显然，根据绘制的形状的复杂性以及QPainterPath，上述内容可能会对性能产生影响.

The above could, obviously, have an impact on performance depending on the complexity of the shape drawn and, hence, the QPainterPath.

(注意:你可以用 代替.)

(Note: rather than using QGraphicsItem::shape you could do a similar thing with QGraphicsItem::opaque instead.)

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