Question

I figured out the solution for my previous question which landed me into new problem.

In the following code im moving an image around a JFrame using arrow keys. but every time i press an arrow key the image seems to flicker which is quite noticeable when a key is pressed continuously.

import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;


public class TestProgram extends JFrame implements KeyListener {
    private BufferedImage TestImage;
    private int cordX = 100;
    private int cordY = 100;

    public TestProgram() {
        setTitle("Testing....");
        setSize(500, 500);
        imageLoader();
        setVisible(true);
    }

    public void imageLoader() {
        try {
            String testPath = "test.png";
            TestImage = ImageIO.read(getClass().getResourceAsStream(testPath));

        } catch (IOException ex) {
            ex.printStackTrace();
        }

        addKeyListener(this);
    }

    @Override
    public void paint(Graphics g) {
        super.paint(g);
        g.drawImage(TestImage, cordX, cordY, this);
    }

    public static void main(String[] args) {
        new TestProgram();
    }


    public void keyPressed(KeyEvent ke) {
        switch (ke.getKeyCode()) {
            case KeyEvent.VK_RIGHT: {
                cordX+=5;
            }
            break;
            case KeyEvent.VK_LEFT: {
                cordX-=5;
            }
            break;
            case KeyEvent.VK_DOWN: {
                cordY+=5;
            }
            break;
            case KeyEvent.VK_UP: {
                cordY-=3;
            }
            break;
        }
        repaint();
    }

    public void keyTyped(KeyEvent ke) {}

    public void keyReleased(KeyEvent ke) {}
}

Is there any solution to avoid that?

EDIT: above is the complete working code. I’m finding it difficult to incorporate doublebuffer in it. can anyone help me in that part?

Answer 1

You have to use a Buffer to get rid of the flickering.
For images, there is the BufferedImage Buffer:

BufferedImage bf = new BufferedImage(getWidth(), getHeight(), BufferedImage.TYPE_INT_RGB);

Then you draw your image to the screen like this:

g.drawImage(bf, 0, 0, null);