JSplitPane divider (One touch expandable)

Question

Hi all,
I am having some problems with the JSplitPane divider. I am using onetouch expandable.
I want to stop the divider moving all the way up to the top of the window when the up arrow is clicked on. When you drag the divider up it stops near the top but doesn't go all the way up. but click on the up arrow on the divider bar and it rises completely to the top. How can I stop this from happening.
I have managed to add an action listener to the buttons on the divider bar, In the action listener I do the following - splitPane.setDividerLocation(0.1);
splitPane.updateUI();
This works but then an exception is thrown -
Exception occurred during event dispatching:
java.lang.NullPointerException
     at javax.swing.plaf.basic.BasicSplitPaneDivider$OneTouchActionHandler.actionPerformed(BasicSplitPaneDivider.java:916)
     at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1450)
     at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(AbstractButton.java:1504)
     at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:378)
     at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:250)
     at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:216)
     at java.awt.Component.processMouseEvent(Component.java:3717)
     at java.awt.Component.processEvent(Component.java:3546)
     at java.awt.Container.processEvent(Container.java:1167)
     at java.awt.Component.dispatchEventImpl(Component.java:2595)
     at java.awt.Container.dispatchEventImpl(Container.java:1216)
     at java.awt.Component.dispatchEvent(Component.java:2499)
     at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:2458)
     at java.awt.LightweightDispatcher.processMouseEvent(Container.java:2223)
     at java.awt.LightweightDispatcher.dispatchEvent(Container.java:2132)
     at java.awt.Container.dispatchEventImpl(Container.java:1203)
     at java.awt.Window.dispatchEventImpl(Window.java:918)
     at java.awt.Component.dispatchEvent(Component.java:2499)
     at java.awt.EventQueue.dispatchEvent(EventQueue.java:336)
     at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:134)
     at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:101)
     at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:96)
     at java.awt.EventDispatchThread.run(EventDispatchThread.java:88)
Can anyone help me out?
thanks,
Paul.

Answer 1

I have partial solution to the above problem but in doing so have encountered another problem that I can see no solution to. Can anyone help?
I have a calss that extends BasicSplitPaneDivider and in this calss i overide the OneTouchActionHandler with a version that sets the top value to be the top of the frame + the height of the component I want left shown. My problem is that this code never runs. The origional OneTouchActionHandler in the BasicSplitPaneDivider runs not my version. How can I get my version to run.
The version in BasicSplitPaneDivider is protected.
This code never runs.
<pre>
* Listeners installed on the one touch expandable buttons.
public class OneTouchActionHandlernew implements ActionListener {
     /** True indicates the resize should go the minimum (top or left)
     * vs false which indicates the resize should go to the maximum.
     private boolean toMinimum;
     OneTouchActionHandlernew(boolean toMinimum) {
     this.toMinimum = toMinimum;
public void actionPerformed(ActionEvent e) {
Insets insets = splitPane.getInsets();
     int lastLoc = splitPane.getLastDividerLocation();
int currentLoc = splitPaneUI.getDividerLocation(splitPane);
     int newLoc;
     // We use the location from the UI directly, as the location the
     // JSplitPane itself maintains is not necessarly correct.
System.out.println("The action listener is being used ");
     if (toMinimum) {
          if (orientation == JSplitPane.VERTICAL_SPLIT) {
          if (currentLoc >= (splitPane.getHeight() -
                    insets.bottom - getDividerSize()))
               newLoc = lastLoc;
          else
               newLoc = insets.top + 40;
          else {
          if (currentLoc >= (splitPane.getWidth() -
                    insets.right - getDividerSize()))
               newLoc = lastLoc;
          else
               newLoc = insets.left;
     else {
          if (orientation == JSplitPane.VERTICAL_SPLIT) {
          if (currentLoc == insets.top)
               newLoc = lastLoc;
          else
               newLoc = splitPane.getHeight() - getHeight() -
               insets.top;
          else {
          if (currentLoc == insets.left)
               newLoc = lastLoc;
          else
               newLoc = splitPane.getWidth() - getWidth() -
               insets.left;
     if (currentLoc != newLoc) {
          splitPane.setDividerLocation(newLoc);
          // We do this in case the dividers notion of the location
          // differs from the real location.
          splitPane.setLastDividerLocation(currentLoc);
} // End of class BasicSplitPaneDivider.LeftActionListener
</pre>