CODEWITHSUNDEEP
javaswingjpanelpaintcomponent
user15071395
user15071395

Reputation:

How to make the paintComponent method work?

I'm now studying Head First Java book. And I've encountered an example that shows how to override paintComponent in order to draw a random color circle over black color rectangle having width and height of the whole JPanel.

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

public class MyDrawPanel extends JPanel {
    public void paintComponent(Graphics g) {
        g.fillRect(0, 0, this.getWidth(), this.getHeight());

        int red = (int)(Math.random() * 255);
        int green = (int)(Math.random() * 255);
        int blue = (int)(Math.random() * 255);

        Color randomColor = new Color(red, green, blue);
        g.setColor(randomColor);
        g.fillOval(70, 70, 100, 100);
    }
}


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

public class SimpleGui3 {
    public static void main(String[] args) {
        JFrame frame = new JFrame();


        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 300);
        frame.setVisible(true);
    }
}

But I am not achieving the expected results: nothing is painted on the panel.

What am I doing wrong? How to make this work?

Upvotes: 0

Views: 524

Answers (1)

olesho
olesho

Reputation: 46

You need two additions in main method for this to work. You have to instantiate the MyDrawPanel() class and then add it to the frame.

MyDrawPanel p = new MyDrawPanel();

and

frame.add(p);

So the main method should be:

    public static void main(String[] args) {
         JFrame frame = new JFrame();
         MyDrawPanel p = new MyDrawPanel();
    
         frame.add(p);
         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         frame.setSize(300, 300);
         frame.setVisible(true);
    }

Upvotes: 0

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