Question

I have a problem.. I have a image painted on my java applet and a for loop to make the x move up 5 every time.. but it leaves behind the old image for a bit then it will erase it..

for(int tohouse = 0; tohouse <= 520; tohouse+=2) {
  try {
    x+=5;
    tohouse+=10;

    if (pos == 0) {
      rectX+=5;
      g.drawImage(picture1,x,150,this);
      pos = 1;
    } else if (pos == 1) {
      rectX+=4;
      g.drawImage(picture2,x,150,this);
      pos = 2;
    } else if (pos == 2) {
      rectX+=5;
      g.drawImage(picture3,x,150,this);
      pos = 0;
    }
  }
}

Heres a image:

Answer 1

You can’t do animation by looping in your paintComponent() or paint() method. Those methods are asking you to paint yourself at a specific point in time (i.e. the current frame).

Instead, you need to decouple the logic of “moving” your sprite from “rendering” your sprite. Look for something like this

private int x;

protected void paintComponent(Graphics g) {
    //draw the images at location x
}

// elsewhere, initialize a javax.swing.Timer to increment x every 15 ms
new Timer(15, new ActionListener() {
    public void actionPerformed(ActionEvent e) {
        x += 5;
        repaint();
    }
}.start();