在JPanel上检测鼠标移动事件

Question

I have a JPanel, which I would like to detect the following events

(1) When the mouse move in

(2) When the mouse move out

The (1) is quick easy. (2) is a bit tricky. Currently, I have to register event at all the components around JPanel. If the neighbor around JPanel detected a mouse move in event, this also means that JPanel is having (2) situation. However, this is a rather dirty away, as I add in new components in the future, this dirty workaround will break.

Another method is to have a timer to monitor the JPanel. If the mouse position is not within JPanel within x seconds, I can consider JPanel is having mouse move out event.

However, this seem a dirty way to me too, as having a separate timer to perform such common task is overkill.

Is there any better way, which Java platform may provide?

Answer 1

Have your class implement MouseListener and add it as a mouse listener on the outermost panel. You should get a mouse-entered event when the mouse moves over the panel, and mouse-exited when it leaves; regardless of whatever components the panel contains.

From the JavaDoc:

void mouseEntered(MouseEvent e) Invoked when the mouse enters a component.

void mouseExited(MouseEvent e) Invoked when the mouse exits a component.