Java- how to clear graphics from a JPanel

anonymous noob picture anonymous noob · May 2, 2015 · Viewed 33k times · Source

I'm creating a simple program where I draw a black oval where I click with my mouse. However I want a new oval to appear and the old one to disappear. How would I go about doing this? I've messed around with the removeAll() method inserted into my mousePressed method, however it isn't working for me. Is the removeAll() method even suitable for this? Or should I use something else? Sorry if the answer is obvious, but I am still new to this and trying to learn. Any advice would be immensely appreciated. Thanks.

import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class PaintPractice extends JPanel implements MouseListener {

    Random rand = new Random(); 
    int x = rand.nextInt(450);
    int y = rand.nextInt(450);

    public PaintPractice(){
        super();
        addMouseListener(this);
    }

    public static void main(String[] args){

        JFrame frame = new JFrame();
        PaintPractice panel = new PaintPractice();

        frame.setSize(500, 500);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setContentPane(panel);        
    }

    public void paint(Graphics g){
        g.setColor(Color.BLACK);
        g.fillOval(x, y, 50, 50);
    }

    @Override
    public void mousePressed(MouseEvent e) {
        x = e.getX();
        y = e.getY();
        removeAll();
        repaint();      
    }

    @Override
    public void mouseClicked(MouseEvent e) {        
    }

    @Override
    public void mouseEntered(MouseEvent e) {        
    }

    @Override
    public void mouseExited(MouseEvent e) {     
    }

    @Override
    public void mouseReleased(MouseEvent e) {       
    }
}

Answer

HiroshiFuu picture HiroshiFuu · May 2, 2015

One possible workaround if u just want to show the newly created oval. Make your frame and panel static, then call frame.setContentPane(panel) in mousePressed.

Another working method is call g.clearRect(0, 0, getWidth(), getHeight()) in paint, but this will make the whole background whitecolor.