drawshapes.java

Java语言

// Draw random lines, rectangles and ovals
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class DrawShapes extends JApplet {
   private JButton choices[];
   private String names[] = { "Line", "Rectangle", "Oval" };
   private JPanel buttonPanel;
   private DrawPanel drawingArea;
   private int width = 300, height = 200;

   public void init()
   {
      drawingArea = new DrawPanel( width, height );

      choices = new JButton[ names.length ];
      buttonPanel = new JPanel();
      buttonPanel.setLayout(
         new GridLayout( 1, choices.length ) );
      ButtonHandler handler = new ButtonHandler();

      for ( int i = 0; i < choices.length; i++ ) {
         choices[ i ] = new JButton( names[ i ] );
         buttonPanel.add( choices[ i ] );
         choices[ i ].addActionListener( handler );
      }

      Container c = getContentPane();
      c.add( buttonPanel, BorderLayout.NORTH );
      c.add( drawingArea, BorderLayout.CENTER );
   }

   public void setWidth( int w )
      { width = ( w >= 0 ? w : 300 ); }

   public void setHeight( int h )
      { height = ( h >= 0 ? h : 200 ); }

   public static void main( String args[] )
   {
      int width, height;

      if ( args.length != 2 ) {  // no command-line arguments
         width = 300;
         height = 200;
      }
      else {
         width = Integer.parseInt( args[ 0 ] );
         height = Integer.parseInt( args[ 1 ] );
      }

      // create window in which applet will execute
      JFrame applicationWindow =
         new JFrame( "An applet running as an application" );

      applicationWindow.addWindowListener(
         new WindowAdapter() {
            public void windowClosing( WindowEvent e )
            {
               System.exit( 0 );
            }
         }
      );

      // create one applet instance
      DrawShapes appletObject = new DrawShapes();
      appletObject.setWidth( width );
      appletObject.setHeight( height );

      // call applet's init and start methods
      appletObject.init();
      appletObject.start();

      // attach applet to center of window
      applicationWindow.getContentPane().add( appletObject );

      // set the window's size
      applicationWindow.setSize( width, height );

      // showing the window causes all GUI components
      // attached to the window to be painted
      applicationWindow.show();
   }

   private class ButtonHandler implements ActionListener {
      public void actionPerformed( ActionEvent e )
      {
         for ( int i = 0; i < choices.length; i++ )
            if ( e.getSource() == choices[ i ] ) {
               drawingArea.setCurrentChoice( i );
               break;
            }
      }
   }
}

// subclass of JPanel to allow drawing in a separate area
class DrawPanel extends JPanel {
   private int currentChoice = -1;  // don't draw first time
   private int width = 100, height = 100;

   public DrawPanel( int w, int h )
   {
      width = ( w >= 0 ? w : 100 );
      height = ( h >= 0 ? h : 100 );
   }

   public void paintComponent( Graphics g )
   {
      super.paintComponent( g );

      switch( currentChoice ) {
         case 0:
            g.drawLine( randomX(), randomY(),
                        randomX(), randomY() );
            break;
         case 1:
            g.drawRect( randomX(), randomY(),
                        randomX(), randomY() );
            break;
         case 2:
            g.drawOval( randomX(), randomY(),
                        randomX(), randomY() );
            break;
      }
   }

   public void setCurrentChoice( int c )
   {
      currentChoice = c;
      repaint();
   }

   private int randomX()
      { return (int) ( Math.random() * width ); }

   private int randomY()
      { return (int) ( Math.random() * height ); }
}