Properly buffering a custom JButton

**Reskaillev** · 04-08-2012, 04:38 PM

So I made a custom JButton class:

Java Code:

package password_example;

import javax.swing.ImageIcon;
import javax.swing.JButton;


@SuppressWarnings("serial")
public class SafeButton extends JButton 
{
	
	public SafeButton()
	{
		super();
		setContentAreaFilled(false); 
		setBorderPainted(false);
		setIcon(createImageIcon("Images/lock.png"));
		setRolloverIcon(createImageIcon("Images/lock_rot.gif"));
		setPressedIcon(getRolloverIcon());
		setFocusPainted(false);
	}
	
	protected static ImageIcon createImageIcon(String path) 
	{
		java.net.URL imgURL = SafeButton.class.getResource(path);
		if (imgURL != null) 
		{
			return new ImageIcon(imgURL);
		} 
		else 
		{
			System.err.println("Couldn't find file: " + path);
			return null;
		}
	}

}

Now the problem is that the transition between lock.png and lock_rot.gif doesn't go smoothly
As you move the cursor inside the JButton the Icon occasionally blinks before properly loading the .gif image

Maybe working with:

Java Code:

	public void update(Graphics g) 
		{
			paintComponent(g);
		}

to enable doublebuffering would work? Not sure if this can apply to the JButton (as I generally use this to double buffer my Applets)

So...how to remove the "blinking"?

**Fubarable** · 04-08-2012, 05:05 PM

I think that to best be able to help you, we need to be able to compile and run your code and experience your problem. One thing I can say is to get rid of your update method override as there's no place for that here.

I tried to reproduce your code using publicly available images but without any "blinking" effect:

Java Code:

import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;

import javax.imageio.ImageIO;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JOptionPane;
import javax.swing.JPanel;

@SuppressWarnings("serial")
public class SafeButton extends JButton {
   public static final String IMAGE_1 = "http://upload.wikimedia.org/wikipedia/"
         + "commons/thumb/b/ba/262326_3cfa1c07_stmrvw.jpg/120px-262326_3cfa1c07_stmrvw.jpg";
   public static final String IMAGE_2 = "http://upload.wikimedia.org/wikipedia/"
         + "commons/thumb/6/6d/3390india.jpg/120px-3390india.jpg";

   public SafeButton() {
      super();
      setContentAreaFilled(false);
      setBorderPainted(false);
      // setIcon(createImageIcon("Images/lock.png"));
      setIcon(createImageIconFromUrl(IMAGE_1));
      // setRolloverIcon(createImageIcon("Images/lock_rot.gif"));
      // setPressedIcon(getRolloverIcon());
      
      setRolloverIcon(createImageIconFromUrl(IMAGE_2));
      setPressedIcon(getRolloverIcon());
      setFocusPainted(false);
   }

   private Icon createImageIconFromUrl(String imgUrl) {
      try {
         BufferedImage img = ImageIO.read(new URL(imgUrl));
         ImageIcon icon = new ImageIcon(img);
         return icon;
      } catch (MalformedURLException e) {
         e.printStackTrace();
      } catch (IOException e) {
         e.printStackTrace();
      }
      return null;
   }

   protected static ImageIcon createImageIcon(String path) {
      java.net.URL imgURL = SafeButton.class.getResource(path);
      if (imgURL != null) {
         return new ImageIcon(imgURL);
      } else {
         System.err.println("Couldn't find file: " + path);
         return null;
      }
   }
   
   public static void main(String[] args) {
      SafeButton safeButton = new SafeButton();
      JPanel panel = new JPanel();
      panel.add(safeButton);
      JOptionPane.showMessageDialog(null, panel);
   }

}