使用 mouseentered 事件突出显示多边形

Question

I am very new to Java Swing, and I am working on an assignment. I have some polygons on my component. When I entered in to a polygon it has to highlight (ie filled with some color).

When I go to next polygon it has to highlight and previous one should be erased (ie normal state). I found some examples but those are using "mousepressed" events, but mine is different.

Answer 1

Have you gone through the MouseListener/MouseMotionListener sections of the Swing tutorials? If not, and if you have nothing written yet, I suggest that you review the tutorials and look at using the MouseMotionListener. You don't want to listen for mouseEntered but more likely mouseMoved. A pseudocode example could be:

in MouseMotionListener or MouseAdapter
   mouseMoved method
      get position of mouse pointer via the MouseEvent parameter.
      For loop through list of Polygons 
         If mouse inside of polygon, highlight it.
         Else, un-highlight it.
      End for loop
   End of mouseMoved method.
end MouseMotionListener or MouseAdapter

Answer 2

java.awt.Polygon has a contains(double x, double y) method that returns true if the x,y mouse coordinates are inside the polygon.

The (x,y) coordinates come from implementing a MouseMotionListener on the Container where you're drawing your shapes and in the implemented public void mouseMoved(MouseEvent e) method you have e.getX() and e.getY() to get the coordinates and check if they're in your polygon(s).