/*
* Copyright (C) The Apache Software Foundation. All rights reserved.
*
* This software is published under the terms of the Apache Software
* License version 1.1, a copy of which has been included with this
* distribution in the LICENSE.txt file.
*/
package org.apache.log4j.lf5.viewer;
import java.awt.*;
import java.awt.event.AdjustmentEvent;
import java.awt.event.AdjustmentListener;
/**
* An AdjustmentListener which ensures that an Adjustable (e.g. a Scrollbar)
* will "track" when the Adjustable expands.
* For example, when a vertical scroll bar is at its bottom anchor,
* the scrollbar will remain at the bottom. When the vertical scroll bar
* is at any other location, then no tracking will happen.
* An instance of this class should only listen to one Adjustable as
* it retains state information about the Adjustable it listens to.
*
* @author Richard Wan
*/
// Contributed by ThoughtWorks Inc.
public class TrackingAdjustmentListener implements AdjustmentListener {
//--------------------------------------------------------------------------
// Constants:
//--------------------------------------------------------------------------
//--------------------------------------------------------------------------
// Protected Variables:
//--------------------------------------------------------------------------
protected int _lastMaximum = -1;
//--------------------------------------------------------------------------
// Private Variables:
//--------------------------------------------------------------------------
//--------------------------------------------------------------------------
// Constructors:
//--------------------------------------------------------------------------
//--------------------------------------------------------------------------
// Public Methods:
//--------------------------------------------------------------------------
public void adjustmentValueChanged(AdjustmentEvent e) {
Adjustable bar = e.getAdjustable();
int currentMaximum = bar.getMaximum();
if (bar.getMaximum() == _lastMaximum) {
return; // nothing to do, the adjustable has not expanded
}
int bottom = bar.getValue() + bar.getVisibleAmount();
if (bottom + bar.getUnitIncrement() >= _lastMaximum) {
bar.setValue(bar.getMaximum()); // use the most recent maximum
}
_lastMaximum = currentMaximum;
}
//--------------------------------------------------------------------------
// Protected Methods:
//--------------------------------------------------------------------------
//--------------------------------------------------------------------------
// Private Methods:
//--------------------------------------------------------------------------
//--------------------------------------------------------------------------
// Nested Top-Level Classes or Interfaces
//--------------------------------------------------------------------------
}
|