I have a custom layout where the principal behavior is to grow and shrink a child JTextArea when the JScrollPane it's in changes in width. The scroll pane has the horizontal scroll bar disabled and the text area is supposed to expand and contract so as to avoid needing a horizontal scroll bar. For a number of months, I worked around this using one of the standard layout managers, but now I need some different functionality.
What's happening is that when the user expands horizontally the scroll pane, the layout manager layoutContainer method is called. It resizes the text area and the text reflows properly. However, when you shrink the scroll pane, layoutContainer is not called and the text area stays fixed. I've put some printlns in the layoutContainer method to make it obvious when it's working and not.
The essential thing to note is that the problem happens when JTextArea.setColumns() is called. I can comment it out and the layoutContainer gets called during resizing (of course, then the text area doesn't get resized.) I've tried also using JTextArea.setSize(), with the same results.
Here's the code:
//----------------------------------------------------------------------------
//----------------------------------------------------------------------------
@SuppressWarnings("serial")
class XTextArea extends JTextArea
{
XTextArea (String text)
{
super (text);
}
public int getColumnWidth()
{
return super.getColumnWidth();
}
}
//----------------------------------------------------------------------------
//----------------------------------------------------------------------------
class PackLeftLayout implements LayoutManager
{
Component viewPort;
Component flexWidthComponent;
int preferredWidth = 0;
int preferredHeight = 0;
//----------------------------------------------------------------------------
// viewPort - if null, compute width as sum of component's preferred width;
// otherwise width will be the viewPort's width.
// flexWidthComponent - if not null, this component width will be sized to right
// justify rightmost component.
public PackLeftLayout (Component viewPort, Component flexWidthComponent)
{
super ();
this.viewPort = viewPort;
this.flexWidthComponent = flexWidthComponent;
}
//----------------------------------------------------------------------------
public void addLayoutComponent(String name, Component comp)
{
}
//----------------------------------------------------------------------------
public void removeLayoutComponent(Component comp)
{
}
//----------------------------------------------------------------------------
// Calculates the preferred size dimensions for the specified container, given the
// components it contains.
// parent - the container to be laid out
// Components layed out left-to-right with no additional spacing.
public Dimension preferredLayoutSize (Container parent)
{
Insets insets = parent.getInsets();
int width = 0;
int height = 0; // will become max of all component's preferred height
// calculate sum of fixed width components - skip the flexwidth component
width = insets.left + insets.right;
for (int i = 0, limit = parent.getComponentCount(); i < limit; i++)
{
Component c = parent.getComponent(i);
if (c.isVisible())
{
if (c != flexWidthComponent)
{
Dimension size = c.getPreferredSize();
if (size.height > height)
height = size.height;
width += size.width;
}
}
}
// determine width of flex width component
if (flexWidthComponent != null)
{
int flexWidth = viewPort.getWidth() - width;
if (flexWidth < 1)
flexWidth = 1;
if (flexWidthComponent instanceof XTextArea)
{
// some trickery here to get the xtextarea to tell us its preferred height
// given a specific width.
int colWidth = ((XTextArea)flexWidthComponent).getColumnWidth();
// the following line causes the failure:
((XTextArea)flexWidthComponent).setColumns (flexWidth / colWidth);
Dimension taSize = flexWidthComponent.getPreferredSize();
width += taSize.width;
if (taSize.height > height)
height = taSize.height;
}
else
{
Dimension size = flexWidthComponent.getPreferredSize();
width += flexWidth;
if (size.height > height)
height = size.height;
}
}
preferredWidth = width; // already include insets
preferredHeight = height + insets.top + insets.bottom;
return new Dimension (preferredWidth, preferredHeight);
}
//----------------------------------------------------------------------------
// Calculates the minimum size dimensions for the specified container, given the
// components it contains.
// parent - the component to be laid out
public Dimension minimumLayoutSize(Container parent)
{
return new Dimension (10, 10); //???
}
static int k = 0;
//----------------------------------------------------------------------------
public void layoutContainer(Container parent)
{
System.out.println ("layout" + (k++));
Insets insets = parent.getInsets();
int left = insets.left;
if (preferredWidth == 0 || preferredHeight == 0)
preferredLayoutSize (parent);
for (int i = 0, limit = parent.getComponentCount(); i < limit; i++)
{
Component c = parent.getComponent(i);
Dimension size = c.getPreferredSize();
c.setBounds (left, insets.top, size.width, preferredHeight);
left += size.width;
}
// force another layout calc
preferredWidth = 0;
}
}
public class ResizablePane extends JFrame
{
public static void main(String[] args)
{
javax.swing.SwingUtilities.invokeLater(
new Runnable() {public void run()
{
new ResizablePane();
}});
}
ResizablePane ()
{
super ("ResizableDemo");
// put a button and text area into a panel, then into a scroll pane
JButton button = new JButton ("button");
XTextArea text = new XTextArea (
"For three years I ran as fast as I could, trying to live and love and learn at " +
"double speed to make up for what Anne-Marie lost. Trying to anesthetize myself " +
"from what Id lost. When I decided to read a book a day and write about it, Id " +
"finally stopped running away.");
text.setLineWrap (true);
text.setWrapStyleWord (true);
JScrollPane scroll = new JScrollPane();
JPanel panel = new JPanel();
panel.setLayout (new PackLeftLayout(scroll.getViewport(), text));
panel.add (button);
panel.add (text);
scroll.setHorizontalScrollBarPolicy (ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
scroll.setViewportView (panel);
getContentPane().add(scroll);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
pack();
setVisible(true);
}
}
