awt browser incompability
I'm doing an applet gui (pure AWT). I have a Canvas inside a ScrollPane. The canvas displays pictures or text of different sizes dynamically, so I reset its size before every paint() with setSize(), then validate(), then getParent().validate() to make sure the ScrollPane resets the scrollbars.
This works fine with the Netscape 6 browser, the scrollbars appear when needed, according to the size of the Canvas.
But it doesn't work with MS IE5: scrollbars don't appear. I fear a browser incompatibility! Suggestions anyone?
miguel
Hi Miguel
I'm doing almost exactly this. I'm adding an array of objects (SimpleCanvas) which extends java.awt.Canvas into ScrollPane. SimpleCanvas can display Images and Text of different sizes dynamically. This works fine in AppletViewer (JDK1.3) But when I run it in browser, The images are not displayed in both IE 5.0 and Netscape 4.7.
You are able to see your applet in NS6 because NS6 directly comes with Java Plugin and IE does not.
Please email me when you solve this problem.
harshapr@comatindia.com
Regards,
Harsha
Here is the message on the java console:
<NETSCAPE 4.7 Java Console>
java.lang.NullPointerException
at sun.awt.windows.WToolkit.checkScrImage(Compiled Code)
at sun.awt.windows.WComponentPeer.checkImage(Compiled Code)
at java.awt.Component.checkImage(Compiled Code)
at java.awt.ImageMediaEntry.getStatus(Compiled Code)
at java.awt.MediaTracker.checkAll(Compiled Code)
at java.awt.MediaTracker.checkAll(Compiled Code)
at SimpleCanvas3.paint(Compiled Code)
at java.awt.Component.dispatchEventImpl(Compiled Code)
* at java.awt.Component.dispatchEvent(Compiled Code)
at java.awt.EventDispatchThread$EventPump.dispatchEvents(Compiled Code)
at java.awt.EventDispatchThread.run(Compiled Code)
at netscape.applet.DerivedAppletFrame$AppletEventDispatchThread.run(Compiled Code)
</NETSCAPE 4.7 Java Console>
<IE 5.0 Java Console>
java.lang.NullPointerException
at com/ms/awt/WToolkit.checkScrImage
at com/ms/awt/WComponentPeer.checkImage
at java/awt/Component.checkImage
at java/awt/ImageMediaEntry.getStatus
at java/awt/MediaTracker.checkAll
at java/awt/MediaTracker.checkAll
at SimpleCanvas3.paint
at com/ms/awt/WComponentPeer.doClearAndPaint
at com/ms/awt/WComponentPeer.paintNode
at com/ms/ui/windowmanager/PaintRequest.run
at com/ms/ui/windowmanager/RunnableMessage.run
at com/ms/awt/WSystemQueue.getMessage
at com/ms/awt/WEventQueue.getNextEvent
at java/awt/EventDispatchThread.run
</IE 5.0 Java Console>
guys,
thank u for your feedback. After hours of tedious debugging, my applet is working fine in IE5. I found several 'hidden' bugs that were accepted by netscape6 but made IE5 crash:
canvas.setSize(getSize().width,myHeight);
I was only concerned with resizing the height. IE5 didn't like that line! (I used 0 instead, result is OK).
- I changed scrollpane.addImpl() to scrollpane.add(). I'm not sure this accomplish anything.
- I overrode getPreferredSize() like Harsha explained (not sure it made any difference).
- I erased my validate() statements.
Sorry, I don't really know more then that!
miguel
Hi miguel.
So you are doing ok. Good.
I'll clarify what I mean by overriding getPreferredSize().
(In response to the mail you sent me.)
Think of it as a substitution for setSize().
When you call setSize, you pass the width and hight values you want:
//setSize(width, height);
if you let the system set the size of the canvas (never calling setSize()) the size is set based upon the preferred size of the component. And the size is set everytime the component is layed out.
therfore:
public void getPreferredSize()
{
return new Dimension(width, height); //width and hight of the size you want.
}
When the size is to change you change the values of width and height member variables.
Then (to make the system lay out the canvas again, and setting the size again) you call
theCanvas.invalidate();
theScrollPane.validate();
";-)
Ragnvald Barth
Software engineer
