rubberband.java

awt图形界面的生成

import java.awt.*;
import java.awt.event.*;

abstract public class Rubberband {
	protected Point anchorPt    = new Point(0,0); 
	protected Point stretchedPt = new Point(0,0);
	protected Point lastPt      = new Point(0,0); 
	protected Point endPt       = new Point(0,0);

	private Component component;
	private boolean   firstStretch = true;
	private boolean   active = false;

	abstract public void drawLast(Graphics g);
	abstract public void drawNext(Graphics g);

	public Rubberband() {
	}
	public Rubberband(Component c) {
		setComponent(c);
	}
	public void setActive(boolean b) {
		active = b;
	}
	public void setComponent(Component c) { 
		component = c; 

		component.addMouseListener(new MouseAdapter() {
			public void mousePressed(MouseEvent event) {	
				if(isActive()) {
					anchor(event.getPoint());
				}
			}
			public void mouseClicked(MouseEvent event) {
				if(isActive())
					end(event.getPoint());
			}
			public void mouseReleased(MouseEvent event) {
				if(isActive())
					end(event.getPoint());
			}
		});
		component.addMouseMotionListener(	
									new MouseMotionAdapter() {
			public void mouseDragged(MouseEvent event) {
				if(isActive())
					stretch(event.getPoint());
			}
		});
	}
	public boolean isActive    () { return active;      }
	public Point   getAnchor   () { return anchorPt;    }
	public Point   getStretched() { return stretchedPt; }
	public Point   getLast     () { return lastPt;      }
	public Point   getEnd      () { return endPt;       }

	public void anchor(Point p) {
        firstStretch = true;
        anchorPt.x = p.x;
        anchorPt.y = p.y;

        stretchedPt.x = lastPt.x = anchorPt.x;
        stretchedPt.y = lastPt.y = anchorPt.y;
    }
    public void stretch(Point p) {
        lastPt.x      = stretchedPt.x;
        lastPt.y      = stretchedPt.y;
        stretchedPt.x = p.x;
        stretchedPt.y = p.y;

        Graphics g = component.getGraphics();
        if(g != null) {
			try {
            	g.setXORMode(component.getBackground());

            	if(firstStretch == true) firstStretch = false;
            	else                     drawLast(g);

            	drawNext(g);
			}
			finally {
				g.dispose();
			}
        }
    }
    public void end(Point p) {
        lastPt.x = endPt.x = p.x;
        lastPt.y = endPt.y = p.y;

        Graphics g = component.getGraphics();
        if(g != null) {
			try {
            	g.setXORMode(component.getBackground());
            	drawLast(g);
			}
			finally {
				g.dispose();
			}
        }
    }
    public Rectangle getBounds() {
      return new Rectangle(stretchedPt.x < anchorPt.x ? 
                           stretchedPt.x : anchorPt.x,
                           stretchedPt.y < anchorPt.y ? 
                           stretchedPt.y : anchorPt.y,
                           Math.abs(stretchedPt.x - anchorPt.x),
                           Math.abs(stretchedPt.y - anchorPt.y));
    }

    public Rectangle lastBounds() {
      return new Rectangle(
                  lastPt.x < anchorPt.x ? lastPt.x : anchorPt.x,
                  lastPt.y < anchorPt.y ? lastPt.y : anchorPt.y,
                  Math.abs(lastPt.x - anchorPt.x),
                  Math.abs(lastPt.y - anchorPt.y));
    }
}