Java window doesn't repaint properly until I resize the window manually

Question

I am using a quite basic setup with a class extending JPanel, which I add to a JFrame.

import java.awt.*;

import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import java.awt.event.*;
import java.awt.geom.RoundRectangle2D;
import java.awt.image.*;
import java.io.*;
import javax.imageio.ImageIO;

public class PinTestMCVE extends JPanel implements ActionListener{

    BufferedImage loadedImage;
    JButton calcButton;

    public static void main(String[] args) {
        new PinTestMCVE();
    }

    public PinTestMCVE() {
        loadedImage = getTestImage();

        JPanel toolbarPanel = new JPanel();
        calcButton = new JButton("calcButton...");
        toolbarPanel.add(calcButton);
        calcButton.addActionListener(this);

        JFrame jf = new JFrame();
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jf.getContentPane().setLayout(new BorderLayout()); 
        jf.getContentPane().add(toolbarPanel, BorderLayout.NORTH);
        jf.getContentPane().add(this, BorderLayout.CENTER);
        jf.setSize(1250, 950);
        jf.setVisible(true);
    }

    public void paintComponent(Graphics g) {
        g.drawImage(loadedImage, 0, 0, this);
    }

    public void actionPerformed(ActionEvent e) {
        System.out.println("ActionEvent " + e.getActionCommand());
        if(e.getSource().equals(calcButton)){
            this.repaint();
        }
    }


//Please ignore the inner workings of this
public static BufferedImage getTestImage(){
    BufferedImage image = new BufferedImage(500, 500, BufferedImage.TYPE_INT_RGB);
    Graphics2D g2d = image.createGraphics();
    g2d.setPaint(Color.GRAY);
    g2d.fillRect ( 0, 0, image.getWidth(), image.getHeight() );
    g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,  RenderingHints.VALUE_ANTIALIAS_ON);
    g2d.setPaint(Color.gray);
    int x = 5;
    int y = 7;
    GradientPaint redtowhite = new GradientPaint(x, y, Color.red, 200, y, Color.blue);
    g2d.setPaint(redtowhite);
    g2d.fill(new RoundRectangle2D.Double(x, y, 200, 200, 10, 10));
    return image;
}
}

What happens is that INITIALLY the window is painted properly, but once paintComponent is called, a strip of the old image (with the same height as the toolbar panel) is visible below the newly painted images - similar to playing card sticking out from a deck. But then, if I manually resize the window by for instance dragging the border, the background is grayed out as it should.

What is going on and how do I fix this?

For better help sooner, post an [MCVE](http://stackoverflow.com/help/mcve) (Minimal, Complete, Verifiable Example). — Andrew Thompson, Jul 18 '14 at 11:21
`jf.pack();` before `setVisible`. To do layout calculations. — Joop Eggen, Jul 18 '14 at 11:38
If the cited duplicate isn't sufficient, please edit your question to include an [mcve](http://stackoverflow.com/help/mcve) that shows your revised approach, as @AndrewThompson suggests — trashgod, Jul 18 '14 at 16:28
You should call `super.paintComponent(g);` as the first line in your `paintComponent` method. — sgbj, Jul 18 '14 at 20:14
@sbat: Good catch; updated; it's not _required_ in this case, but a good habit; more [here](http://www.oracle.com/technetwork/java/painting-140037.html). — trashgod, Jul 18 '14 at 20:51
@trashgod If you increase the preferred size of the panel to, let's say 600 by 600, and remove the call to `super.paintComponent(g);` in your code, it exhibits the same behavior that the OP is experiencing. Adding `super.paintComponent(g);` _is_ the correct answer. See this [screenshot](http://s15.postimg.org/u9y7j75wr/Untitled.png). — sgbj, Jul 18 '14 at 21:01
@sbat: Thank you for looking at this; sadly, I can't reproduce the effect on Mac OS X; the corresponding UI delegate on Windows may not be opaque by default. — trashgod, Jul 18 '14 at 21:20

score 3 · Answer 1 · edited May 23 '17 at 11:50

As outlined here, you need to pack() the frame before calling setVisible(). You can override getPreferredSize() to specify a suitable initial Dimension. Also consider using a Border. See also Initial Threads.

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.awt.geom.RoundRectangle2D;
import java.awt.image.*;

public class PinTestMCVE extends JPanel implements ActionListener{

    private static final int SIZE = 200;
    BufferedImage loadedImage;
    JButton calcButton;

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                new PinTestMCVE();
            }
        });
    }

    public PinTestMCVE() {
        loadedImage = getTestImage();
        JPanel toolbarPanel = new JPanel();
        calcButton = new JButton("calcButton...");
        toolbarPanel.add(calcButton);
        calcButton.addActionListener(this);

        JFrame jf = new JFrame();
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jf.add(toolbarPanel, BorderLayout.NORTH);
        jf.add(this, BorderLayout.CENTER);
        jf.pack();
        jf.setLocationRelativeTo(null);
        jf.setVisible(true);
    }

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

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawImage(loadedImage, 0, 0, this);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        System.out.println("ActionEvent " + e.getActionCommand());
        if(e.getSource().equals(calcButton)){
            this.repaint();
        }
    }


    //Please ignore the inner workings of this
    public static BufferedImage getTestImage(){
        BufferedImage image = new BufferedImage(SIZE, SIZE, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2d = image.createGraphics();
        g2d.setPaint(Color.GRAY);
        g2d.fillRect ( 0, 0, image.getWidth(), image.getHeight() );
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,  RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.setPaint(Color.gray);
        GradientPaint redtowhite = new GradientPaint(5, 5, Color.red, SIZE, 5, Color.blue);
        g2d.setPaint(redtowhite);
        g2d.fill(new RoundRectangle2D.Double(5, 5, SIZE - 10, SIZE - 10, 10, 10));
        return image;
    }
}

Thank you so much. I was not aware of the mechanics of pack() and getPreferedSize till now. — user1507316, Jul 19 '14 at 11:55

Java window doesn't repaint properly until I resize the window manually

1 Answers1