AppletTalk.com Java discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  JList + JScrollPane + ensureIndexIsVisible() = Corruption          AppletTalk.com Forum Index -> Java GUI Toolkits View previous topic :: View next topic   Author Message Jason Teagle Guest Posted: Fri Nov 21, 2003 11:02 pm    Post subject: JList + JScrollPane + ensureIndexIsVisible() = Corruption Windows XP Home SP1 java version "1.4.1-rc" Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.1-rc-b19) Java HotSpot(TM) Client VM (build 1.4.1-rc-b19, mixed mode) I have a JList in a JScrollPane. I'm trying to get it to scroll to the latest item added (i.e., the bottom of the list) after each line is added. So I tried using ensureIndexIsVisible(). The problem is, doing that causes corruption - some of the text is rendered OUTSIDE of the JList, off the bottom. If that spurious writing is covered by another window and then uncovered, causing a repaint (no new lines added to the list in between), the spurious writing doesn't come back, as expected. I also tried instead grabbing the vertical scrollbar from the scroll pane and setting its value to the maximum, thus also scrolling to the bottom; it had the same weird effect. I have a GIF (which I can't post here) that clearly shows the writing being scribbled below the limit of the box, and can explain the problem better than words. If anyone has an urge to see it, e-mail me privately. Any ideas why this happens? It happens repeatedly, not just a one-off fluke. Any other suggestions of how I might get this list scrolled to the bottom each time? I'm actually trying to make a log output window, where outgoing commands are one colour and incoming responses are another, which is why I want it always showing the last line logged. If I use a JTextArea, it works fine, but I can't get the colours. I tried using a JEditorPane to use text/html for the colours but that was horribly jerky and blinky (yes, I'm inventing "blinky" as a word). A JList with custom rendering gives the colours great, and doesn't jerk or blink... but this scrolling is the last hurdle. -- -- Jason Teagle [email]jason (AT) teagster (DOT) co.uk[/email] Back to top Mr.Cube Guest Posted: Sat Nov 22, 2003 4:52 pm    Post subject: Re: JList + JScrollPane + ensureIndexIsVisible() = Corruptio Jason Teagle wrote: Quote: Windows XP Home SP1 java version "1.4.1-rc" Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.1-rc-b19) Java HotSpot(TM) Client VM (build 1.4.1-rc-b19, mixed mode) I have a JList in a JScrollPane. I'm trying to get it to scroll to the latest item added (i.e., the bottom of the list) after each line is added. So I tried using ensureIndexIsVisible(). The problem is, doing that causes corruption - some of the text is rendered OUTSIDE of the JList, off the bottom. If that spurious writing is covered by another window and then uncovered, causing a repaint (no new lines added to the list in between), the spurious writing doesn't come back, as expected. Make sure that you perform all UI-actions on the Event-Dispatch-Thread. Use SwingUtilities.invokeLater() to execute UI-actions on the EDT. Kees. Back to top Mr.Cube Guest Posted: Sat Nov 22, 2003 4:54 pm    Post subject: Re: JList + JScrollPane + ensureIndexIsVisible() = Corruptio .. A JList with custom rendering gives the Quote: colours great Custom Rendering ? Make sure that you respect the clipBounds ! Kees. Back to top Jason Teagle Guest Posted: Sun Nov 23, 2003 5:44 pm    Post subject: Re: JList + JScrollPane + ensureIndexIsVisible() = Corruptio Quote: . A JList with custom rendering gives the colours great Custom Rendering ? Make sure that you respect the clipBounds ! I may have misled you there: by custom rendering I mean: m_logWindow = new JList(m_list); m_logWindow.setCellRenderer(new JListCellRenderer() ); and JListCellRenderer looks like this: private class JListCellRenderer extends JLabel implements ListCellRenderer { public Component getListCellRendererComponent(JList list, Object value, ....) { setText( ( (JColouredLabel)value).getText() ); setIcon( ( (JColouredLabel)value).getIcon() ); setHorizontalAlignment( ( (JColouredLabel)value).getHorizontalAlignment() ); setBackground(list.getBackground() ); setForeground( ( (JColouredLabel)value).getColour() ); setEnabled(list.isEnabled() ); setFont(list.getFont() ); setOpaque(true); return this ; } } This was customised from a sample in Sun's Java API doc pages, so if I'm not respecting the clip rect correctly then neither did their sample {:v) -- -- Jason Teagle [email]jason (AT) teagster (DOT) co.uk[/email] Back to top Jason Teagle Guest Posted: Sun Nov 23, 2003 6:04 pm    Post subject: Re: JList + JScrollPane + ensureIndexIsVisible() = Corruptio Quote: Make sure that you perform all UI-actions on the Event-Dispatch-Thread. Use SwingUtilities.invokeLater() to execute UI-actions on the EDT. That certainly seems to have stopped the corruption - thankyou for reminding me of that essential point. My mistake. Unfortunately ensureIndexIsVisible() is now doing absolutely nothing... and while scrolling the scrollbar to its maximum is amost working, there's clearly a lag between when it updates the UI component (the JList) with the new items in the model and when it updates the maximum value of the scroll bar... since it doesn't always scroll to the true bottom. I'll have to find another strategy to achieve that effect. -- -- Jason Teagle [email]jason (AT) teagster (DOT) co.uk[/email] Back to top Kleopatra Guest Posted: Mon Nov 24, 2003 11:44 am    Post subject: Re: JList + JScrollPane + ensureIndexIsVisible() = Corruptio Jason Teagle wrote: Quote: Unfortunately ensureIndexIsVisible() is now doing absolutely nothing... and hmm... should work. "no effect" sounds as if the list were not yet ready with its internal update. How/when exactly do you trigger the scrolling? 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