Flickering in JFrame

Question

Im working on a small game that will be for the enjoyment of my freinds and if come into an error. The Screen will flicker the images. I know this is from the canvas rendering the image every single frame. But I dont know how to stop it from rendering every frame. I was looking for help. This is a bit of code in my main, JFrameBuilder, and JCanvas class to show what im doing.

https://pastebin.com/renyzgXx

package main;

import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

import entity.Dragon;
import imageBuilders.Image;


public class Main {

public static JFrameBuilder jf ;

public static void main(String[] args){

    jf = new JFrameBuilder("Tutorial");


    try {
        JCanvas.addImage(new Image(ImageIO.read(new File("C:/Users/Eddie/Desktop/testprog2/Tutorial game/src/imgs/Dragon.png")), null,100,100));
        JCanvas.addImage(new Image(ImageIO.read(new File("C:/Users/Eddie/Desktop/testprog2/Tutorial game/src/imgs/rocket.png")), null,100,100));
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    int x = 0;

    Dragon d = new Dragon(jf,x);
    while(jf.isActive()){
    jf.update(jf.getGraphics());

    JCanvas.changeImageXandY(d.calculateX(), d.calculateY(), 0);
    System.out.println(d.calculateX());
    delay(16);
    }
}


public static void delay(long ms){
    try {
        Thread.sleep(ms);
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}


}

https://pastebin.com/ERisWs6V

package main;

import java.awt.BorderLayout;

import javax.swing.JFrame;

public class JFrameBuilder extends JFrame{
/**
 * Author: Kingmo100
 */
private static final long serialVersionUID = -8535971463237805125L;
private static final int WIDTH = 1000;
private static final int HEIGHT = 500;
private static JCanvas jp;
public JFrameBuilder(String title){
    super(title);
    this.setVisible(true);
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setSize(WIDTH, HEIGHT);
    this.setLayout(new BorderLayout()); 
    jp = new JCanvas();
    jp.setSize(WIDTH, HEIGHT);
    jp.setLocation(10, HEIGHT + 10);
    jp.setAlignmentX(10);
    jp.setAlignmentY(10);
    jp.paintComponents(this.getGraphics());
    jp.setVisible(true);
    System.out.println(jp);
    this.add(jp, BorderLayout.CENTER);
    this.getContentPane();

}

public static JCanvas getJCanvas(){
    return jp;
}

public JFrame getFrame(){
    return this;
}
}

https://pastebin.com/6EGkHj6r

package main;

import java.awt.Graphics;
import java.awt.event.KeyListener;
import java.util.ArrayList;
import java.util.List;

import javax.swing.JPanel;

import imageBuilders.Image;

public class JCanvas extends JPanel {

private static List<Image> li = new ArrayList<Image>();

/**
 * 
 */
private static final long serialVersionUID = -4456984789525563682L;


public JCanvas(){
    super();
}
@Override
public void paint(Graphics g){
    super.paint(g);
    for(Image i: li){
    try{    
    g.drawImage(i.getImage(), i.getX(), i.getY(), i.getImageObserver());
    }catch(NullPointerException e){
    }
    }
}

public static void addImage(Image i){
    li.add(i);
}

public static void removeImageinIndice(int i){
    li.remove(i);
}

public static void changeImageInIndice(int i, Image i2){
    li.add(i, i2);
}

public static void clearImages(){
    li.clear();
}

public static Image getImageinIndice(int i){
    return li.get(i);
}

public static boolean changeImageXandY(int x, int y, int ii){
    Image im = li.get(ii);

    im.setX(x);
    System.out.println(im.getX());
    im.setY(y);
    li.set(ii, im);
    return true;

}


public KeyListener getKeyListener(){
    return this.getKeyListener();
}


}

Answer 1

Swing components (including JPanel) are already double buffered by default, so you won't benefit by trying to implement your own double buffering. Try overriding paintComponent() instead of overriding paint() (which is the old AWT way to do things).

paint() actually includes a call to three different methods, one of which is paintComponent() , so when you're overriding paint() , you're painting borders and all children twice, which is probably why your UI is flickering.

For more details, read The Java Tutorial and for even more details, read this Oracle tech note .