JScrollPane vertical bar is defaulting to the bottom

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Debs - 31 Aug 2006 09:45 GMT

Hi,

I have a JScrollPane for a large panel, when it displays the vertical
bar is at the bottom. I want it at the top - I have various other
JScrollPanes elsewhere that default to the top as expected.

I believe the difference may be that this panel contains JTextAreas,
and I have read that setting the caret position can help. However, with
it having multiple, I'm not sure what to do. I have tried setting the
focus and caret position in the first JTextArea, but this did not work.

Sample code:

=======================================
...

JPanel innerDetailPanel = new JPanel(new GridBagLayout());
innerDetailPanel.setBorder(null);

int gridy=0;

GridBagConstraints detailPanelConstraints = new GridBagConstraints();
detailPanelConstraints.gridx = 0;
detailPanelConstraints.gridy = gridy;
detailPanelConstraints.weightx=0.5;
detailPanelConstraints.fill = GridBagConstraints.HORIZONTAL;
detailPanelConstraints.insets = new Insets(5, 1, 1, 1);

//title
JLabel titleLabel = new JLabel("Title label", JLabel.CENTER);
titleLabel.setBackground(TITLECOLOR);
titleLabel.setOpaque(true);
titleLabel.setFont(TITLEFONT);
innerDetailPanel.add(titleLabel, detailPanelConstraints);
gridy++

for(int i=0;i<names.length; i++) {

    detailPanelConstraints.gridx = 0;
    detailPanelConstraints.gridy = gridy;
    detailPanelConstraints.weightx=0.5;

    String name = names[i];
    JTextArea nameValue = new JTextArea(name);

    nameValue.setLineWrap(true);
    nameValue.setEditable(false);
    nameValue.setBackground(getContentPane().getBackground());
    innerDetailPanel.add(nameValue, detailPanelConstraints);
    gridy++;

}

JPanel northAlign = new JPanel(new BorderLayout());
northAlign.add(innerDetailPanel, BorderLayout.NORTH);
JScrollPane locationDetailPanel = new JScrollPane(northAlign,
JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
Border compoundBorder = BorderFactory.createCompoundBorder(
new EmptyBorder(5,20,5,20), new LineBorder(Color.DARK_GRAY));
locationDetailPanel.setBorder(new CompoundBorder(compoundBorder, new
EmptyBorder(5,5,5,5)));

...

=======================================

I tried the same code but using JLabel rather than a textarea, and the
scroll bar is at the top as expected.
The reason I'm using the textareas is to ensure text correctly wraps. I
know you can make JLabels wrap using <html> but the labels steal as
much room as they can, rather than just wrapping within the expected
cell space. The JTextAreas correctly display what I want.

Like I said above, I also tried setting the focus and caret position on
the first (top most) JTextArea, but this did not work. I've tried a
few methods for setting the position of the scroll bar, but they do not
work either.

Any suggestions would be much appreciated, thank you.

Reply to this Message

Michael Rauscher - 31 Aug 2006 11:16 GMT

Debs schrieb:

> Hi,
>
[quoted text clipped - 6 lines]
> it having multiple, I'm not sure what to do. I have tried setting the
> focus and caret position in the first JTextArea, but this did not work.

A few days ago someone asked the same in c.l.j.programmer - but for the
horizontal direction.

The behaviour is caused by JComponent that reaches scrollRectToVisible
up the component tree. Knowing this, the solution is obvious: just
intercept the chain.

To intercept the chain you'd have to put JTextArea into a container that
implements it's own version of scrollRectToVisible. E.g. a JViewport or
another panel that overrides this method.

So the solution for the code you gave in your previous post is simple:

JPanel innerDetailPanel = new JPanel(new GridBagLayout()) {
public void scrollRectToVisible( Rectangle r ) {}
};

Bye
Michael

Reply to this Message

ickz - 31 Aug 2006 11:34 GMT

> Debs schrieb:
> > Hi,
[quoted text clipped - 27 lines]
> Bye
> Michael

That did the trick!
Your explanation is very clear and useful, and the solution is very
neat.

Thank you!
Debs

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JScrollPane vertical bar is defaulting to the bottom

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