CODEWITHSUNDEEP
javaswinggraphics
jamie
jamie

Reputation: 176

Paint component is stuck in an infinite loop causing a stackoverflow error. Why is this?

I'm creating a JFrame window, creating a 'ball' object, and adding this ball object to the jframe window. What's the problem exactly?

public class Main {
    public static void main(String[] args){
        JFrameWindow j= new JFrameWindow(300,500);
        Ball b = new Ball(150,200,10,20);
        j.add(b);
    }
}


import javax.swing.*;
import java.awt.*;

public class JFrameWindow extends JFrame {
    int width;
    int height;

    public JFrameWindow(int width,int height){
        this.width=width;

    //blah


import javax.swing.*;
import java.awt.*;

public class Ball extends JPanel{
    int sX,sY;
    Color color;
    int speed;
    int height;
    int width;

    public Ball(int sX,int sY,int height,int width){
        this.sX=sX;
        this.sY=sY;
        this.color=color;
        this.speed=speed;
        this.height=height;
        this.width=width;
    }

    public void paintComponent(Graphics g){
        super.paint(g);
        Graphics2D g2d=(Graphics2D)g;
        //g2d.setColor(color.RED);
        g2d.fillOval(sX,sY,width,height);
    }
}

Basically, when I run this program, 'super.paint(g)' gets called over and over again and I don't know why this is. I haven't set the ball to move in a timer or anything so why's the problem occurring?

Upvotes: 2

Views: 469

Answers (2)

Hovercraft Full Of Eels
Hovercraft Full Of Eels

Reputation: 285405

As Abhinav states, the problem is that super.paint(g); is re-starting the painting chain which then calls the JPanel's paintComponent(g) method which calls super.paint(g) which calls the JPanel's paintComponent(g) method which calls... and on and on

The solution is simple -- call the correct super method, the one that matches the painting method that you're calling:

@Override
protected void paintComponent(Graphics g) { // protected, not public

    // super.paint(g);       // ******** REMOVE *********
    super.paintComponent(g); // ******** ADD *********

    Graphics2D g2d = (Graphics2D) g;
    g2d.fillOval(sX, sY, width, height);
}

Upvotes: 3

user11264239
user11264239

Reputation:

super.paint() calls the paintComponent() function, so obvioulsy, this is an endless recursion. Therefore, you will never get out of the code. Probably call the function at an interval of time.

Upvotes: 2

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