bball4one.java

书籍"Java_面向事件编程"的附带光盘代码

import objectdraw.*;

// This program allows the user to drag a fancy BBall around the screen.
// Points are awarded when the ball is placed in the basket.
public class BBall4One extends WindowController{

   // Location of the display
   private static final int DISPLAY_Y = 200;
   private static final int DISPLAYSIZE = 16; // in points

   // Location and dimensions of the hoop
   private static final int HOOPTOP = 50;
   private static final int HOOPWIDTH = 80;
   private static final int HOOPHEIGHT = 35;

   // Initial location and dimensions of the ball
   private static final int BALLY = 300;
   private static final int BALLSIZE = 40;

   // the Text object which displays the count
   private Text display;

   // the oval that represent the hoop
   private FramedOval hoop;

   // the other oval (that represents the ball)
   private BBall ball;

   // whether or not player grabbed the ball with the mouse
   private boolean carryingBall;

   // the number of points
   private int score;

   // the last previous known location of the mouse
   private Location lastMouse;

   
   // initialize the counter and the text message
   public void begin() {
      score = 0;
      display = new Text("Your score is 0", 0, DISPLAY_Y, canvas);
      display.setFontSize(DISPLAYSIZE);
      display.move((canvas.getWidth() - display.getWidth())/2, 0);

      hoop = new FramedOval( (canvas.getWidth() - HOOPWIDTH)/2, HOOPTOP, 
                                                 HOOPWIDTH, HOOPHEIGHT, canvas);

      ball = new BBall( (canvas.getWidth() - BALLSIZE)/2, BALLY, 
                             BALLSIZE, canvas);

   }

   // Note where mouse is depressed
   public void onMousePress(Location point)
   {
      carryingBall = ball.contains(point);
      lastMouse = point;
   }

   // Move the ball
   public void onMouseDrag(Location point)
   {
      if ( carryingBall )
      {
         ball.move( point.getX() - lastMouse.getX(),
                    point.getY() - lastMouse.getY()
                                        );
         lastMouse = point;
      }
   }

   // increment the counter and update the text
   public void onMouseRelease(Location point) {
      if ( carryingBall && hoop.contains(point) ) {
         score = score + 2;
         display.setText("Your score is " + score );
      }
      
      ball.reset();
   }
}