Clearing JPanel

I am making a program in which there is a square that changes its x and y positions when a key is pressed. The square move开发者_Go百科s but the the old square is still there. How do I remove/clear everything from a panel before I repaint it? Calling removeAll had no effect.

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Presumably your code includes custom paintComponent() logic. The key thing to observe is what does your panel look like when you do not override paintComponent()? An empty (or cleared) panel:

Thus the solution is to invoke the paintComponent() method of the parent type on the panel, before executing your custom paintComponent() logic:

public class CustomPanel extends JPanel {
  @Override
  public void paintComponent(Graphics g) {
    super.paintComponent(g); // first draw a clear/empty panel
    // then draw using your custom logic.
  }
}

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I think this should work.

g.clearRect (0, 0, panel.getWidth(), panel.getHeight());

Also, you could keep the old location of the square and just clear that rather than clear the whole background.