放置位置渲染

This is a more advanced topic and most people do not need to worry about it. However, if you have a custom component you will need to handle the drop location rendering yourself.

You can register to be notified whenever the dropLocation property changes. You would listen for this change and do your own rendering of the drop location in a custom renderer for the component or in the paintComponent method, using the getDropLocation method.

Here is an example of listening for the dropLocation property:

class Repainter extends PropertyChangeListener {
    public void propertyChange(PropertyChangeEvent pce) {
        repaintDropLocation(pce.getOldValue());
        repaintDropLocation(pce.getNewValue());
    }
}

comp.addPropertyChangeListener("dropLocation", newRepainter());

Here is an example of the paintComponent approach:

public void paintComponent(Graphics g) {
    super.paintComponent(g);

    DropLocation loc= getDropLocation();
    if (loc == null) {
        return;
    }

    renderPrettyIndicatorAt(loc);
}