Drawing rectangles on a JPanel

Question

I have a JScrollPane and on top of it I have a JPanel named \'panel1\'. I want some rectangles to be drawn on this JPanel.

I have a class named DrawRectPanel which e

Answer 1

instead of adding

contentPane.add(new DrawRectPanel());

you should do

contentPane.add(panel1);

Because you already have new DrawRectPanel in panel1. But in your code you are adding another instance of DrawRectPanel in contentPane. And never added panel1 in none of your container.

Answer 2

to fix your problem, change "paintComponent" to "paint" when the window repaints automatically, it should work.

Answer 3

still no idea,

for example

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import javax.swing.JComponent;
import javax.swing.JFrame;

public class CustomComponent extends JFrame {

    private static final long serialVersionUID = 1L;

    public CustomComponent() {
        setTitle("Custom Component Graphics2D");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public void display() {
        add(new CustomComponents());
        pack();
        // enforces the minimum size of both frame and component        
        setMinimumSize(getSize());
        setVisible(true);
    }

    public static void main(String[] args) {
        CustomComponent main = new CustomComponent();
        main.display();
    }
}

class CustomComponents extends JComponent {

    private static final long serialVersionUID = 1L;

    @Override
    public Dimension getMinimumSize() {
        return new Dimension(100, 100);
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(400, 300);
    }

    @Override
    public void paintComponent(Graphics g) {
        int margin = 10;
        Dimension dim = getSize();
        super.paintComponent(g);
        g.setColor(Color.red);
        g.fillRect(margin, margin, dim.width - margin * 2, dim.height - margin * 2);
    }
}