JSplitPane SetDividerLocation Problem

Question

I have a JSplitPane which when shown should split the pane by 50%.

Now on giving an argument of 0.5 (as suggested) to setDividerLocation, Java seems to treat it as a normal number instead of a percentage. As in, the divider, instead of going to the middle of the pane, is almost at the start of the left pane (the pane is vertically split). Any work arounds?

Answer 1

Am I missing something? There seem to be a lot of rather convoluted answers to this question... but I think a simple setResizeWeight(0.5) would solve the issue ... it's described in the SplitPane Tutorial

Answer 2

The setDividerLocation( double ) method only works on a "realized" frame, which means after you've packed or made the frame visible.

The setDividerLocation( int ) method can be used at any time.

Answer 3

You can only set the split pane divider's location as a percentage when the split pane is visible. You can tap into the split pane owner's events to determine when its OK to set the divider's location. For example:

public class MyFrame extends JFrame {

  public MyFrame() {

    final JSplitPane splitPane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT);
    // ... set up the split pane, and add to the frame ...

    // Listen for the frame's "shown" event.

    addComponentListener(new ComponentAdapter() {

      @Override
      public void componentShown(ComponentEvent componentEvent) {

        // Set the divider location to 20%.
        // This works because we know the pane is visible.

        splitPane.setDividerLocation(.2);

        // Stop listening for "shown" events.

        removeComponentListener(this);
      }

    });

    pack();
  }
}

Answer 4

this fixes it:

public class JSplitPane3 extends JSplitPane {
    private boolean hasProportionalLocation = false;
    private double proportionalLocation = 0.5;
    private boolean isPainted = false;

    public void setDividerLocation(double proportionalLocation) {
        if (!isPainted) {
            hasProportionalLocation = true;
            this.proportionalLocation = proportionalLocation;
        } else {
            super.setDividerLocation(proportionalLocation);
        }
    }

    public void paint(Graphics g) {
        super.paint(g);
        if (!isPainted) {
            if (hasProportionalLocation) {
                super.setDividerLocation(proportionalLocation);
            }
            isPainted = true;
        }
    }

}

Answer 5

If you're happy for the divider to move to the middle every time you resize the pane, you could add a ComponentListener and have its componentResized method call setDividerLocation(0.5).