这篇接着上篇内容，在飞机的基础上加入了飞机跟随手指移动，还有飞行路线左右方向随机移动的敌机，看样子像喝醉酒一样，呵呵......

汗死，这个太原始了，初学嘛，呵呵

代码还是接着上篇的基础上改的

package WangLi.Graphics.MoveBack;

import java.util.Random;
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.graphics.Paint;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.Display;
import android.view.View;
import android.view.MotionEvent;  
import android.view.Window;
import android.view.WindowManager;

public class MoveBack extends Activity
{
	@Override
	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		//去掉标题
		requestWindowFeature(Window.FEATURE_NO_TITLE);
		//全屏显示
		getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, 
				WindowManager.LayoutParams.FLAG_FULLSCREEN);
		setContentView(new MyView(this));
	}
	class MyView extends View
	{
		//记录背景位图的实际高度
		final int BACK_HEIGHT = 1700;
		//背景图片
		private Bitmap back;
		private Bitmap plane;
		private Bitmap enemyPlane;
		//背景图片的开始位置
		final int WIDTH = 370;
		final int HEIGHT = 440;
		private int startY = BACK_HEIGHT - HEIGHT;		
		private float ememyY = BACK_HEIGHT - HEIGHT;	
		private float ememyX;
		private float planeX;
		private float planeY;
		//桌面高度
		private int tableWidth;
		//桌面宽度
		private int tableHeight;
		public MyView(Context context)
		{
			super(context);
			//获取窗口管理器
			WindowManager windowManager = getWindowManager();
			Display display = windowManager.getDefaultDisplay();
			//获得屏幕宽高
			tableWidth = display.getWidth();
			tableHeight = display.getHeight();
			
			// TODO Auto-generated constructor stub
			back = BitmapFactory.decodeResource(context.getResources()
				, R.drawable.back_img);
			plane = BitmapFactory.decodeResource(context.getResources()
				, R.drawable.plane);			
			
			int planeWidth = plane.getWidth();
			int planeHeight = plane.getHeight();
			
			//敌机
			enemyPlane= BitmapFactory.decodeResource(context.getResources()
					, R.drawable.enemy_plane);
			
			int enemyWidth = enemyPlane.getWidth();
			int enemyHeight = enemyPlane.getHeight();
			
			
			planeX = (tableWidth - planeWidth) / 2; //飞机横向初始停靠位置在屏幕中间位置
			planeY = tableHeight - planeHeight * 2; //飞机纵向初始停靠位置在离屏幕底端朝上一个机身位置
			
			ememyX = (tableWidth - planeWidth) / 2;
			
			final Handler handler = new Handler()
			{
				public void handleMessage(Message msg)
				{
					if (msg.what == 0x123)
					{
						//重新开始移动
						if (startY <= 0)
						{
							startY = BACK_HEIGHT - tableHeight;
						}
						else
						{
							startY -= 3;
						}
						if(ememyY >= tableHeight)
						{
							ememyY = 0;
						}
						else
						{
							ememyY += 5;
						}
						if(ememyX > tableWidth || ememyX < 0)
						{
							ememyX = (tableWidth - enemyPlane.getWidth())/2;
						}
					}
					invalidate();
				}
			};
			new Timer().schedule(new TimerTask()
			{
				@Override
				public void run()
				{
					handler.sendEmptyMessage(0x123);					
				}
				
			}, 0 , 10);
		}
		@Override
		public void onDraw(Canvas canvas)
		{
			// 根据原始位图和Matrix创建新图片
			Bitmap bitmap2 = Bitmap.createBitmap(back, 0, startY
				, tableWidth , tableHeight);
			// 绘制新位图
			canvas.drawBitmap(bitmap2, 0 , 0  , null);
			// 绘制飞机
			canvas.drawBitmap(plane, planeX , planeY  , null);	
			//绘制敌机
			Random rand = new Random();
			//敌机随机的横向左右移动
			ememyX = ememyX + rand.nextInt(20) + (-rand.nextInt(20));
			Bitmap enemyPlaneCopy = Bitmap.createBitmap(enemyPlane);
			canvas.drawBitmap(enemyPlaneCopy, ememyX , ememyY , null);
		}		
		
		//onTouchEvent事件之后会自动调用onDraw事件
		public boolean onTouchEvent(MotionEvent event) { 
			int planeWidth = plane.getWidth();
			int planeHeight = plane.getHeight();
			//让飞机跟随手指移动，并且不能飞出屏幕以外的范围
			if((event.getX() > 0 && event.getX() < tableWidth - planeWidth) && (event.getY() > 0 && event.getY() < tableHeight - planeHeight))
			{
				planeX = event.getX();
				planeY = event.getY(); 
				return true; 
			}
			else
				return false;
	    } 
	}
}