Drawn object doesn't clear previous rectangle after key is pressed

Question

My code will not clear the previous rectangle. I thought by using the getRect() and then using repaint() in my keyPressed() method, that would solve the problem.

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.KeyEvent;
import java.awt.geom.Rectangle2D;
import javax.swing.Icon;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.geom.AffineTransform;
import java.awt.geom.Arc2D;
import java.awt.geom.PathIterator;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.util.ArrayList;

import javax.swing.Icon;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;


public class Rectangle extends JFrame implements KeyListener{

private int height;
private int width;
private int x;
private int y;
private Graphics2D g2;



public Rectangle(int width, int height,int x, int y)
{
    this.height = height;
    this.width = width;
    this.x = x;
    this.y = y;

   JLabel label = new JLabel();


    setSize(1000,1000);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setLocationRelativeTo(null);
    setVisible(true);


    label.addKeyListener(this);
    label.setFocusable(true);
    label.setOpaque(true);
    label.addKeyListener(this);
    this.add(label);
    setVisible(true);
    label.requestFocusInWindow();

}


public void keyPressed(KeyEvent e)
{   

    if (e.getKeyCode() == KeyEvent.VK_DOWN)
    {
        g2.clearRect(x, y, width, height);
        repaint();
        y = y + 5;
        repaint();
    }
    if (e.getKeyCode() == KeyEvent.VK_LEFT)
    {
        g2.clearRect(x, y, width, height);
        repaint();
        x = x - 5;
        repaint();
    }
    if (e.getKeyCode() == KeyEvent.VK_UP)
    {
        g2.clearRect(x, y, width, height);
        repaint();
        y = y - 5;
        repaint();
    }
    if (e.getKeyCode() == KeyEvent.VK_RIGHT)
    {
        g2.clearRect(x, y, width, height);
        x = x + 5;
        repaint();
    }
}


public void keyReleased(KeyEvent e) {}

public void keyTyped(KeyEvent e) {}




public void paint(Graphics g) {

    g2 = (Graphics2D) g;
    g2.drawRect(x, y, width, height);

}

}

Test Method:

public class Test {

public static void main(String[] args)
{
    Rectangle rectangle = new Rectangle(400,200,500,500);

}
}

Answer 1

1. setVisible(true) should be last code line in public Rectangle(..., because you added JComponents to the already visible Swing GUI.

2. JFrame isn't focusable for KeyEvent, by default.

3. put JPanel to JFrame's CENTER area, by default: myFrame.add(myPanel).

4. override getPreferredSize for JPanel instead of setting for JFrame size; sizing should be intialized by calling myFrame.pack().

5. JPanel must be focusable for receiving an KeyEvent, setFocusable(true); use KeyBindings instead of hunting for focus in JComponent hierarchy.

6. override paintComponent for JPanel; 1st code line should be super.paintComponent, otherwise painting artifacts will occur.

Answer 2

Could you add more detail? From what I can see, you may want to make a clear button & method.