一个“雷电”游戏的雏形

package org.crazyit.event;
import java.util.Random;
import java.util.Timer;
import java.util.Timer;
import java.util.TimerTask;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;

import java.util.TimerTask;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.Display;
import android.view.KeyEvent;
import android.view.View;
import android.view.View.OnKeyListener;
import android.view.Window;
import android.view.WindowManager;
public class plane extends Activity{
    Bitmap plane;
    Bitmap plane1;
    private int back_height=1700;
    private int width = 320;
    private int height = 480;
    Bitmap back;
    int starty = back_height-height;
    // 桌面的宽度
    private int tableWidth;
    // 桌面的高度
    private int tableHeight;
    // 飞机的坐标
    public float currentX;
    public float currentY;
    // 敌机小球纵向的运行速度
    private int ySpeed = 10;
    Random rand = new Random();
    // 返回一个-0.5~0.5的比率，用于控制小球的运行方向。
    private double xyRate = rand.nextDouble() - 0.5;
    // 小球横向的运行速度
    private int xSpeed = (int) (ySpeed * xyRate * 2);
    // ballX和ballY代表小球的座标
    private int ballX = rand.nextInt(200) + 20;
    private int ballY = rand.nextInt(10) + 20;
    // 游戏是否结束的旗标
    private boolean isLose = false;

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        // 去掉窗口标题
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        // 全屏显示
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);
        // 创建PlaneView组件
        final GameView gameView = new GameView(this);
        setContentView(gameView);
        // 获取窗口管理器
        WindowManager windowManager = getWindowManager();
        Display display = windowManager.getDefaultDisplay();
        
        // 获得屏幕宽和高
        tableWidth = display.getWidth();
        tableHeight = display.getHeight();
        currentX = tableWidth/2;
        currentY = tableHeight-40;
        
            // TODO Auto-generated constructor stub
            //定义飞机图片
        
                
        final Handler handler = new Handler()
        {
            public void handleMessage(Message msg)
            {
                if (msg.what == 0x123)
                {
                    gameView.invalidate();
                    if (starty <= 0)
                    {
                        starty = back_height-height;
                    }
                    else
                    {
                        starty -= 10;
                    }
                    
                }
            }
        };

        gameView.setOnKeyListener(new OnKeyListener()
        {
            @Override
            public boolean onKey(View source, int keyCode, KeyEvent event)
            {
                // 获取由哪个键触发的事件
                switch (event.getKeyCode())
                {
                    // 控制挡板左移
                    case KeyEvent.KEYCODE_DPAD_LEFT:
                        if (currentX > 0)
                            currentX -= 10;
                        break;
                    // 控制挡板右移
                    case KeyEvent.KEYCODE_DPAD_RIGHT:
                        if (currentX < tableWidth)
                            currentX += 10;
                        break;
                    case KeyEvent.KEYCODE_DPAD_DOWN:
                        if(currentY<tableHeight)
                            currentY+=10;
                        break;
                    case KeyEvent.KEYCODE_DPAD_UP:
                        if(currentY>0)
                            currentY-=10;
                        break;
                }
                // 通知planeView组件重绘
                gameView.invalidate();
                return true;
            }
        });
        final Timer timer = new Timer();
        timer.schedule(new TimerTask()
        {

            @Override
            public void run()
            {
                // 如果小球碰到左边边框
                if (ballX <= 0 || ballX >= tableWidth)
                {
                    xSpeed = -xSpeed;
                }
                // 如果小球高度超出了球拍位置，且横向不在球拍范围之内，游戏结束。
                if (ballY >= tableHeight||(ballY == currentY && ballX ==currentX))
                {
                    timer.cancel();
                    // 设置游戏是否结束的旗标为true。
                    isLose = true;
                }
                // 小球座标增加
                ballY += ySpeed;
                ballX += xSpeed;
                // 发送消息，通知系统重绘组件
                handler.sendEmptyMessage(0x123);
            }
        }, 0, 100);
    }

    class GameView extends View
    {
        public GameView(Context context)
        {
            super(context);
            setFocusable(true);
            plane = BitmapFactory.decodeResource(context.getResources()
                    , R.drawable.plane);
                setFocusable(true);
                plane1 = BitmapFactory.decodeResource(context.getResources()
                        , R.drawable.plane1);
                    setFocusable(true);
            back =BitmapFactory.decodeResource(context.getResources()
                    , R.drawable.back_img);
            setFocusable(true);
                    
        }
        

        // 重写View的onDraw方法，实现绘画
        public void onDraw(Canvas canvas)
        {
            Paint paint = new Paint();
            
            // 如果游戏已经结束
            if (isLose)
            {
                paint.setColor(Color.RED);
                paint.setTextSize(40);
                canvas.drawText("游戏已结束", 50, 200, paint);
            }
            // 如果游戏还未结束
            else
            {
                // 设置颜色，并绘制小球
                Bitmap back2 = Bitmap.createBitmap(back, 0, starty
                        , width , height);
                canvas.drawBitmap(back2, 0, 0, paint);
                canvas.drawBitmap(plane1 , ballX , ballY , paint);    
                canvas.drawBitmap(plane , currentX , currentY , paint);    
            }
        }
    }


}