stillpatheticpong.java

书籍"Java_面向事件编程"的附带光盘代码

import objectdraw.*;

// plays a slightly more advanced version of pong where the ball
// can bounce off of the paddle
public class StillPatheticPong extends WindowController{
    
    // Margin between court and window boundaries
    private static final int
        COURT_MARGIN = 50;
    
    // dimensions of the paddle
    private static final int
        PADDLE_WIDTH = 50,
        PADDLE_HEIGHT = 20;

    FilledRect paddle;
    FramedRect boundary;        // the boundary of the playing area.
    
    public void begin()
    {
        // make the playing area
        boundary = new FramedRect(COURT_MARGIN, COURT_MARGIN,
                                  canvas.getWidth() - 2*COURT_MARGIN,
                                  canvas.getHeight() - 2*COURT_MARGIN,
                                  canvas);
        
        // make the paddle
        paddle =
            new FilledRect((canvas.getWidth()-PADDLE_WIDTH)/2,
                           boundary.getY() + boundary.getHeight() - PADDLE_HEIGHT -1,
                           PADDLE_WIDTH, PADDLE_HEIGHT,
                           canvas);
    }
    
    public void onMouseClick(Location point)
    {
        // make a new ball when the player clicks
        new BouncingBall(boundary.getX() + boundary.getWidth()/2,
                         boundary.getY(), 
                         paddle,
                         canvas).start();
    }
    
    public void onMouseMove(Location point)
    {
        if ( point.getX() < boundary.getX() )
            {
                // place paddle at left edge of the court
                paddle.moveTo( boundary.getX(),
                               paddle.getY() );
            }
        else if ( point.getX() > boundary.getX() + boundary.getWidth() - PADDLE_WIDTH)
            {
                // place paddle at right edge of the court
                paddle.moveTo( boundary.getX() + boundary.getWidth() - PADDLE_WIDTH,
                               paddle.getY());
            }
        else
            {
                // keep the edge of the paddle lined up with the mouse
                paddle.moveTo( point.getX(),
                               paddle.getY());
            }
    }
    
}