Swing resize slow/jumpy

Question

I made my own BottomBar with a simple gradient extending JComponent and adjusting the paintComponent() method.

Then I add it to the SOUTH of my JFrame which uses BorderLayout.

Everything looks correct at the beginning. When I resize the frame the BottomBar gets repainted and set to the new position correctly. The think is, it happens a few milliseconds to late, so that one can see the JFrame 's background for a second.

The funny thing is, that when I set the execution environment to Java-SE 1.6 it works... (instead of 1.7) Also, Im running it on a mac, if that makes a difference.

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Code - JButton Example

import java.awt.BorderLayout;
import java.awt.EventQueue;
import javax.swing.JButton;
import javax.swing.JFrame;


public class Main {

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

            @Override
            public void run() {
                JFrame frame = new JFrame("Resize Example");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new JButton(), BorderLayout.SOUTH);
                frame.pack();
                frame.setLocationByPlatform(true);
                frame.setVisible(true);
            }
        });
    }
}

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Code - BottomBar Example

Main:

public class Main {
    public static void main(String args[]){
        Frame window = new Frame();
        window.setSize(500, 400);
        window.setVisible(true);
    }
}

Frame:

import java.awt.BorderLayout;

import javax.swing.JFrame;


public class Frame extends JFrame{
    private static final long serialVersionUID = 1L;

    public Frame() {
        setLayout( new BorderLayout() );
        getContentPane().add( BorderLayout.SOUTH, new BottomBar() );
    }
}

BottomBar

import java.awt.Color;
import java.awt.Dimension;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;

import javax.swing.JComponent;

public class BottomBar extends JComponent {
    private static final long serialVersionUID = 1L;

    public BottomBar() {
        setSize(200, 30);
        setPreferredSize( new Dimension(200, 30) );
    }

    protected void paintComponent(Graphics g) {
        Graphics2D g2 = (Graphics2D)g;

        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);

        GradientPaint gradient = new GradientPaint(0, 0, new Color(185, 185, 185), 0, getHeight() , new Color(151, 151, 151) );
        g2.setPaint(gradient);
        g2.fillRect(0, 0, getWidth(), getHeight());

        g2.setColor( new Color(64, 64, 64) );
        g2.drawLine(0, 0, getWidth(), 0);
        g2.setColor( new Color(215, 215, 215) );
        g2.drawLine(0, 1, getWidth(), 1);
    }
}

Answer 1

I am unable to reproduce the effect you describe on 1.6; you might try the sscce below on 1.7. Note, several suggestions for your example:

• Avoid setXxxxSize(), as discussed here. If you just want a 30 pixel high bar in SOUTH, override getPreferredSize() as shown below. If you later decide to add components, you'll need to add a layout manager.

  @Override
  public Dimension getPreferredSize() {
      return new Dimension(0, 30);
  }
  

• Use pack() to let the Window adopt the preferred sizes of the enclosed components. I've added an arbitrary size JPanel to the CENTER; resize the frame to see how the bar grows horizontally in SOUTH.

• Swing GUI objects should be constructed and manipulated only on the event dispatch thread.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;

/** @see https://stackoverflow.com/a/13610367/230513 */
public class Main {

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

            @Override
            public void run() {
                JFrame frame = new JFrame("BottomBar");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new JPanel() {

                    @Override
                    public Dimension getPreferredSize() {
                        return new Dimension(320, 240);
                    }
                }, BorderLayout.CENTER);
                frame.add(new BottomBar(), BorderLayout.SOUTH);
                frame.pack();
                frame.setLocationByPlatform(true);
                frame.setVisible(true);
            }
        });
    }

    private static class BottomBar extends JComponent {

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(0, 30);
        }

        @Override
        protected void paintComponent(Graphics g) {
            Graphics2D g2 = (Graphics2D) g;
            g2.setRenderingHint(
                RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);
            GradientPaint gradient = new GradientPaint(
                0, 0, new Color(185, 185, 185),
                0, getHeight(), new Color(151, 151, 151));
            g2.setPaint(gradient);
            g2.fillRect(0, 0, getWidth(), getHeight());
            g2.setColor(new Color(64, 64, 64));
            g2.drawLine(0, 0, getWidth(), 0);
            g2.setColor(new Color(215, 215, 215));
            g2.drawLine(0, 1, getWidth(), 1);
        }
    }
}