Hi Tomas,
I think I am able to reproduce problem you observe (second
image does not appear after first mouse click).
However, it seems that problem here has no relation to the
image loading, but rather is related to components layout.
I've noticed that after construction, second instance of JLabel
(jl2) has meaningful preferred size but actual size is w=0,h=0.
I guess this is because this component is not bound to container
yet and dimension is not calculated. As a result offset calculation
procedure (method movePanel() in your example) shifts viewpoint
outside of the frame border.
Explicit request to doLayout() method after setting new view helps
to workaround the problem (cause recalculation of actual size).
On other hand explicit layout requests are typically bad thing
to do. You may want to ask Swing team what is the best way to
proceed (Swing forum is here:
http://forums.java.net/jive/forum.jspa?forumID=74&start=0)
Thanks,
Andrew
Thomas Busey wrote:
I'm having problems loading images when using JLabels in conjunction
with a JViewport. The following code demonstrates the problem. It will
create a frame that displays one of two images. The user cycles between
the two images by clicking within the frame, so that the second image is
effectively a zoom of the first. The first JLabel loads fine, and is the
first displayed. The first time the images are cycled (after a user
clicks), the second image comes up as invalid. Subsequent cycling
results in normal behavior. I've tried utilizing the built in
Mediatracker, as well as explicitly setting the JViewport's view to try
to explicitly load the second image. It seems like the second image
doesn't load the first time, although changing the image loading order
doesn't change the behavior; the image that is shown after the click is
never valid the first time, but is the second time.
I'd appreciate any insights people might have. Below is a complete
program that isolates the issue.
Thanks,
Tom
// Begin Code --------------------------------
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Test implements MouseListener {
int view = 1;
JViewport viewport;
/* REPLACE WITH YOUR OWN IMAGES */
String p1 = "C:/Documents and
Settings/dwyatte/Desktop/fingerzoom/Img/ABLF1.jpg";
String p2 = "C:/Documents and
Settings/dwyatte/Desktop/fingerzoom/Img/ABLF2.jpg";
JLabel jl1, jl2;
ImageIcon ii1, ii2;
JFrame frame;
/* creates a frame with two images. cycle between them by clicking
within the frame.
* first click will result in an invalid second image, but subsequent
clicks result
* in normal behavior */
public Test() {
ii1 = new ImageIcon(p1);
ii2 = new ImageIcon(p2);
jl1 = new JLabel(ii1);
jl2 = new JLabel(ii2);
frame = new JFrame("Test");
frame.setSize(800, 600);
frame.getContentPane().setLayout(new BorderLayout());
viewport = new JViewport();
viewport.setView(jl1);
frame.getContentPane().add(viewport, BorderLayout.CENTER);
frame.addMouseListener(this);
frame.setVisible(true);
}
public void mouseReleased(MouseEvent e) {}
public void mousePressed(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}
public void mouseEntered(MouseEvent e) {}
public void mouseClicked(MouseEvent e) {
System.out.println("jl1 is " + jl1);
System.out.println();
/* Here, you can see that the size of jl2
* is invalid on the first click */
System.out.println("jl2 is " + jl2);
System.out.println();
if(view == 1) {
viewport.setView(jl2);
movePanel(0,0);
view = 2;
}
else {
viewport.setView(jl1);
movePanel(0,0);
view = 1;
}
}
public void movePanel(int xmove, int ymove) {
Point pt = new Point(xmove, ymove);
/* getMaxXExtent and getMaxYExtent will systematically
* fail on the first click because jl2's size is invalid */
pt.x = Math.max(0, pt.x);
pt.x = Math.min(getMaxXExtent(), pt.x);
pt.y = Math.max(0, pt.y);
pt.y = Math.min(getMaxYExtent(), pt.y);
viewport.setViewPosition(pt);
}
/* viewport.getView().getWidth is image width
* viewport.getWidth() is frame width. */
public int getMaxXExtent() {
return viewport.getView().getWidth() - viewport.getWidth();
}
public int getMaxYExtent() {
return viewport.getView().getHeight() - viewport.getHeight();
}
public static void main(String args[]) {
new Test();
}
}
Thomas Busey, PhD
Associate Professor
Department of Psychological and Brain Sciences
Program in Cognitive Science
Indiana University, Bloomington
1101 E. 10th St
Bloomington, IN, 47405
(812) 855-4261
[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>
www.indiana.edu/~busey
AIM / IChat AV: [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]> (video feed)
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