drawfigurepanel.java

《Java实例入门》所有实例的源代码。所有的源文件都是.java文件

package drawfigure;

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

public class DrawFigurePanel extends Panel {
  Point startPoint = new Point(0,0);
  Point lastEndPoint = new Point(0,0);
  Point thisEndPoint = new Point(0,0);
  Point finalEndPoint = new Point(0,0);
  public String drawStyle = null;
  boolean figureState = false;
  boolean firstDraw = true;

  public DrawFigurePanel(){
    addMouseListener(new MouseAdapter(){
      public void mousePressed(MouseEvent e){
        startPoint.x = lastEndPoint.x = thisEndPoint.x = e.getPoint().x;
        startPoint.y = lastEndPoint.y = thisEndPoint.y = e.getPoint().y;
        setCursor(Cursor.getPredefinedCursor(Cursor.CROSSHAIR_CURSOR));
        figureState = true;
      }
      public void mouseReleased(MouseEvent e){
        finalEndPoint.x = e.getPoint().x;
        finalEndPoint.y = e.getPoint().y;
        setCursor(Cursor.getPredefinedCursor(Cursor.DEFAULT_CURSOR));
        Graphics g = getGraphics();
        g.setXORMode(getBackground());
        if(firstDraw)
          drawFigure(g,startPoint,finalEndPoint);
        g.dispose();
        figureState = false;
        firstDraw = true;
      }
    });
    addMouseMotionListener(new MouseMotionAdapter(){
      public void mouseDragged(MouseEvent e){
        Graphics g = getGraphics();
        g.setXORMode(getBackground());
        if(figureState){
          lastEndPoint.x = thisEndPoint.x;
          lastEndPoint.y = thisEndPoint.y;
          thisEndPoint.x = e.getPoint().x;
          thisEndPoint.y = e.getPoint().y;
        }
        if(firstDraw){
          drawFigure(g,startPoint,thisEndPoint);
          firstDraw = false;
        }else {
          drawFigure(g,startPoint,lastEndPoint);
          drawFigure(g,startPoint,thisEndPoint);
        }
        g.dispose();
      }
    });
  }


  public void setDrawStyle(String style){
    drawStyle = style;
  }

  public void drawFigure(Graphics g,Point start,Point end){
    if(drawStyle == "line"){
      g.drawLine(start.x,start.y,end.x,end.y);
    }else if(drawStyle == "rect"){
      int x = start.x ,y = start.y;
      if(end.x < start.x) x = end.x;
      if(end.y < start.y) y = end.y;
      g.drawRect(x,y,Math.abs(end.x - start.x),Math.abs(end.y - start.y));
    }else if(drawStyle == "oval"){
      int x = start.x ,y = start.y;
      if(end.x < start.x) x = end.x;
      if(end.y < start.y) y = end.y;
      g.drawOval(x,y,Math.abs(end.x-start.x),Math.abs(end.y - start.y));
    }
  }

}