drawingview.java

高级java2 大学教程(含源码,经典的Java学习教程

// DrawingView.java
// DrawingView is a view of a DrawingModel that draws shapes using
// the Java2D API.
package com.deitel.advjhtp1.drawing.view;

// Java core packages
import java.awt.*;
import java.awt.geom.*;
import java.awt.event.*;
import java.util.*;
import java.util.List;

// Java extension packages
import javax.swing.*;

// Deitel packages
import com.deitel.advjhtp1.drawing.model.*;
import com.deitel.advjhtp1.drawing.model.shapes.*;

public class DrawingView extends JPanel implements Observer {
   
   // model for which this is a view
   private DrawingModel drawingModel;

   // construct DrawingView for given model
   public DrawingView( DrawingModel model ) 
   {
      // set DrawingModel
      drawingModel = model;
      
      // set background color
      setBackground( Color.white );
      
      // enable double buffering to reduce screen flicker
      setDoubleBuffered( true );
   }

   // set DrawingModel for view to given model
   public void setModel( DrawingModel model )
   {
      if ( drawingModel != null )
         drawingModel.deleteObserver( this );
      
      drawingModel = model;   
      
      // register view as observer of model
      if ( model != null ) {
         model.addObserver( this );
         repaint();
      }
   }

   // get DrawingModel associated with this view
   public DrawingModel getModel() 
   { 
      return drawingModel; 
   }
   
   // repaint view when update received from model
   public void update( Observable observable, Object object ) 
   { 
      repaint(); 
   }

   // overridden paintComponent method for drawing shapes
   public void paintComponent( Graphics g ) 
   {
      // call superclass paintComponent
      super.paintComponent( g );
      
      // create Graphics2D object for given Graphics object
      Graphics2D g2D = ( Graphics2D ) g;
      
      // enable anti-aliasing to smooth jagged lines
      g2D.setRenderingHint( RenderingHints.KEY_ANTIALIASING, 
         RenderingHints.VALUE_ANTIALIAS_ON );
      
      // enable high-quality rendering in Graphics2D object
      g2D.setRenderingHint( RenderingHints.KEY_RENDERING, 
         RenderingHints.VALUE_RENDER_QUALITY );
      
      // draw all shapes in model
      drawShapes( g2D );
   }
   
   // draw shapes in model
   public void drawShapes( Graphics2D g2D )
   {
      // get Iterator for shapes in model
      Iterator iterator = drawingModel.getShapes().iterator();
      
      // draw each MyShape in DrawingModel
      while( iterator.hasNext() ) {    
         MyShape shape = ( MyShape ) iterator.next();
         shape.draw( g2D );
      }
   }
   
   // get preferred size for this component
   public Dimension getPreferredSize()
   { 
      return new Dimension( 320, 240 ); 
   }
      
   // insist on preferred size for this component
   public Dimension getMinimumSize()
   { 
      return getPreferredSize(); 
   }
  
   // insist on preferred size for this component
   public Dimension getMaximumSize()
   { 
      return getPreferredSize(); 
   }
   
   // add DrawingView as Observer of DrawingModel when
   // DrawingView obtains screen resources
   public void addNotify()
   {
      super.addNotify();     
      drawingModel.addObserver( this );
   }
   
   // remove DrawingView as Observer of DrawingModel when
   // DrawingView loses screen resources
   public void removeNotify()
   {
      super.removeNotify();     
      drawingModel.deleteObserver( this );
   }
}

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 * (C) Copyright 2002 by Deitel & Associates, Inc. and         *
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