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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
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package javademo.swing.scroll.ScrollDemo;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import javax.swing.ImageIcon;
import javax.swing.JLabel;
import javax.swing.Scrollable;
import javax.swing.SwingConstants;
/* ScrollablePicture.java is used by ScrollDemo.java. */
@SuppressWarnings("serial")
public class ScrollablePicture extends JLabel implements Scrollable, MouseMotionListener
{
private int maxUnitIncrement = 1;
private boolean missingPicture = false;
public ScrollablePicture(ImageIcon i, int m)
{
super(i);
if (i == null)
{
missingPicture = true;
setText("No picture found.");
setHorizontalAlignment(CENTER);
setOpaque(true);
setBackground(Color.white);
}
maxUnitIncrement = m;
// Let the user scroll by dragging to outside the window.
setAutoscrolls(true); // enable synthetic drag events
addMouseMotionListener(this); // handle mouse drags
}
// Methods required by the MouseMotionListener interface:
public void mouseMoved(MouseEvent e)
{
}
public void mouseDragged(MouseEvent e)
{
// The user is dragging us, so scroll!
Rectangle r = new Rectangle(e.getX(), e.getY(), 1, 1);
scrollRectToVisible(r);
}
public Dimension getPreferredSize()
{
if (missingPicture)
{
return new Dimension(320, 480);
}
else
{
return super.getPreferredSize();
}
}
public Dimension getPreferredScrollableViewportSize()
{
return getPreferredSize();
}
public int getScrollableUnitIncrement(Rectangle visibleRect, int orientation, int direction)
{
// Get the current position.
int currentPosition = 0;
if (orientation == SwingConstants.HORIZONTAL)
{
currentPosition = visibleRect.x;
}
else
{
currentPosition = visibleRect.y;
}
// Return the number of pixels between currentPosition
// and the nearest tick mark in the indicated direction.
if (direction < 0)
{
int newPosition = currentPosition - (currentPosition / maxUnitIncrement) * maxUnitIncrement;
return (newPosition == 0) ? maxUnitIncrement : newPosition;
}
else
{
return ((currentPosition / maxUnitIncrement) + 1) * maxUnitIncrement - currentPosition;
}
}
public int getScrollableBlockIncrement(Rectangle visibleRect, int orientation, int direction)
{
if (orientation == SwingConstants.HORIZONTAL)
{
return visibleRect.width - maxUnitIncrement;
}
else
{
return visibleRect.height - maxUnitIncrement;
}
}
public boolean getScrollableTracksViewportWidth()
{
return false;
}
public boolean getScrollableTracksViewportHeight()
{
return false;
}
public void setMaxUnitIncrement(int pixels)
{
maxUnitIncrement = pixels;
}
}