repaint() in Java

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Java GUI repaint() problem?

I write a Java code, but I have a trouble with GUI problem. When I add a component into JFrame object, then I call repaint() method in order to update the GUI but it doesn't work. But when I minimize or resize this frame, the GUI is updated.

Here is my code:

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

    frame.setSize(460, 500);
    frame.setTitle("Circles generator");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    frame.setVisible(true);

    String input = JOptionPane.showInputDialog("Enter n:");
    int n = Integer.parseInt(input);

    CircleComponent component = new CircleComponent(n);
    frame.add(component);
    component.repaint();
}

mKorbel · Accepted Answer · 2012-01-14T00:02:44.287

If you added JComponent to already visible Container, then you have call

frame.getContentPane().validate();
frame.getContentPane().repaint();

for example

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;

public class Main {

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.setSize(460, 500);
        frame.setTitle("Circles generator");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
              frame.setVisible(true);
           }
        });

        String input = JOptionPane.showInputDialog("Enter n:");
        CustomComponents0 component = new CustomComponents0();
        frame.add(component);
        frame.getContentPane().validate();
        frame.getContentPane().repaint();
    }

    static class CustomComponents0 extends JLabel {

        private static final long serialVersionUID = 1L;

        @Override
        public Dimension getMinimumSize() {
            return new Dimension(200, 100);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(300, 200);
        }

        @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);
        }
    }
}

Now make sure the code in the main method runs on the EDT and it would even be better — Robin, Jan 13 '12 at 22:24

score 5 · Answer 2 · answered Jan 13 '12 at 16:17

5

Simply write :

frame.validate();
frame.repaint();

That will do .

Regards

answered Jan 13 '12 at 16:17

nIcE cOw

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right, there no reason to declare for ContentPane +1 – mKorbel Jan 13 '12 at 16:19
1

@mKorbel : I was late for the answer, but your answer using ContentPane(), i guess is much better. Some say it's a good practise. But thankx for the points. Regards – nIcE cOw Jan 13 '12 at 16:22

score 3 · Answer 3 · edited Jan 13 '12 at 16:32

3

You're doing things in the wrong order.

You need to first add all JComponents to the JFrame, and only then call pack() and then setVisible(true) on the JFrame

If you later added JComponents that could change the GUI's size you will need to call pack() again, and then repaint() on the JFrame after doing so.

edited Jan 13 '12 at 16:32

mKorbel

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answered Jan 13 '12 at 16:11

Hovercraft Full Of Eels

283,665
25
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373

score 2 · Answer 4 · answered Jan 13 '12 at 16:03

2

You may need to call frame.repaint() as well to force the frame to actually redraw itself. I've had issues before where I tried to repaint a component and it wasn't updating what was displayed until the parent's repaint() method was called.

answered Jan 13 '12 at 16:03

aoi222

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I change component.repaint() to frame.repaint(), but it doesn't work. – Jan 13 '12 at 16:09

repaint() in Java

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