如何使用SurfaceView实现鱼儿游动动画

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
 android:orientation="vertical" 
 android:layout_width="match_parent" 
 android:layout_height="match_parent"> 
 <com.example.liuyan.testbutfly.FishView 
  android:layout_width="match_parent" 
  android:layout_height="match_parent" /> 
</LinearLayout> 

public class FishView extends SurfaceView implements SurfaceHolder.Callback{ 
 private SurfaceHolder holder; 
 private UpdateViewThread updatethread; 
 private boolean hasSurface; 
 private Bitmap back; 
 private Bitmap[] fishs; 
 private int fishIndex = 0;//绘制第几张鱼 
 //鱼的初始位置 
 private float fishx = 778; 
 private float fishy = 500; 
 private float fishSpeed = 6; //鱼的游动速度 
 //鱼的游动角度 
 private int fishAngle = new Random().nextInt(60); 
 Matrix matrix = new Matrix(); 
 
 public FishView(Context context) { 
  super(context); 
  Log.i("mydate" , "开始"); 
  //获取surfaceview的surfaceholder，并将该类的实例作为其callback 
  holder = getHolder(); 
  holder.addCallback(this);//以自身作为callback,回调方法 
  hasSurface = false; 
  back = BitmapFactory.decodeResource(context.getResources() , R.drawable.fishbg);//背景 
  int[] id = new int[]{R.drawable.fish0 , R.drawable.fish1 , R.drawable.fish2 ,R.drawable.fish3 ,R.drawable.fish4 ,R.drawable.fish5 ,R.drawable.fish6 ,R.drawable.fish7 ,R.drawable.fish8, R.drawable.fish9}; 
  fishs = new Bitmap[10]; 
  //初始化 鱼游动的10张图 
  for (int i = 0 ; i < 10 ; i++){ 
   try { 
    fishs[i] = BitmapFactory.decodeResource(context.getResources() , id[i]); 
   } catch (Exception e){ 
    e.printStackTrace(); 
   } 
  } 
  Log.i("mydate" , "结束"); 
 } 
 
 public FishView(Context context, AttributeSet attrs) { 
  super(context, attrs); 
  Log.i("mydate" , "开始"); 
  //获取surfaceview的surfaceholder，并将该类的实例作为其callback 
  holder = getHolder(); 
  holder.addCallback(this);//以自身作为callback,回调方法 
  hasSurface = false; 
  back = BitmapFactory.decodeResource(context.getResources() , R.drawable.fishbg);//背景 
  int[] id = new int[]{R.drawable.fish0 , R.drawable.fish1 , R.drawable.fish2 ,R.drawable.fish3 ,R.drawable.fish4 ,R.drawable.fish5 ,R.drawable.fish6 ,R.drawable.fish7 ,R.drawable.fish8, R.drawable.fish9}; 
  fishs = new Bitmap[10]; 
  //初始化 鱼游动的10张图 
  for (int i = 0 ; i < 10 ; i++){ 
   try { 
//    int fishId = (Integer) R.drawable.class.getField("fish" + i).get(null);//反射机制获取图片 
//    Log.i("mydate" , " "+ fishId); 
    fishs[i] = BitmapFactory.decodeResource(context.getResources() , id[i]); 
   } catch (Exception e){ 
    e.printStackTrace(); 
   } 
  } 
  Log.i("mydate" , "结束"); 
 } 
 
 
 public void resume(){ 
  //创建和启动 图片更新线程 
  if (updatethread == null){ 
   updatethread = new UpdateViewThread(); 
   if (hasSurface == true){ 
    updatethread.start(); 
   } 
  } 
 } 
 
 public void pause(){ 
  //停止 图像更新线程 
  if (updatethread != null){ 
   updatethread.requestExitAndWait(); 
   updatethread = null; 
  } 
 } 
 
 
 @Override 
 public void surfaceCreated(SurfaceHolder holder) { //surfaceview被创建时回调该方法 
  hasSurface = true; 
  resume(); //开启线程更新 
 } 
 
 @Override 
 public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {//surfaceview改变时回调该方法 
  if (updatethread != null){ 
   updatethread.onWindowResize(width , height); 
  } 
 } 
 
 @Override 
 public void surfaceDestroyed(SurfaceHolder holder) {//surfaceview销毁时回调该方法 
  hasSurface = false; 
  pause(); //停止线程更新 
 } 
 
 class UpdateViewThread extends Thread{ 
  //定义图像是否更新完成的标志 
  private boolean done; 
 
  public UpdateViewThread() { 
   super(); 
   done = false; 
  } 
 
  @Override 
  public void run() { 
   SurfaceHolder surfaceholder = holder; 
   //循环绘制，直到线程停止 
   while (!done){ 
    Canvas canvas = surfaceholder.lockCanvas();//锁定surfaceview,准备绘制 
    //绘制背景 
    canvas.drawBitmap(back , 0 , 0 , null); 
    //鱼游出屏幕外，重新初始化鱼的位置 
    if (fishx < 0 ){ 
     fishx = 778; 
     fishy = 500; 
     fishAngle = new Random().nextInt(60); 
    } 
    if (fishy < 0){ 
     fishx = 778; 
     fishy = 500; 
     fishAngle = new Random().nextInt(60); 
    } 
    //用matrix控制鱼的旋转角度和位置 
    matrix.reset(); 
    matrix.setRotate(fishAngle);//下面的位置计算看图片的解释如下： 
    matrix.postTranslate(fishx -= fishSpeed * Math.cos(Math.toRadians(fishAngle)) , fishy -= fishSpeed * Math.sin(Math.toRadians(fishAngle))); 
    canvas.drawBitmap(fishs[fishIndex++%fishs.length] , matrix , null); 
    surfaceholder.unlockCanvasAndPost(canvas);//解锁canvas，渲染绘制图像 
    try { 
     Thread.sleep(60); 
    } catch (Exception e){ 
     e.printStackTrace(); 
    } 
   } 
  } 
 
  public void requestExitAndWait() { 
   //将绘制线程 标记为完成 ,并合并到主线程中 
   done = true; 
   try { 
    join(); 
   } catch (Exception e){ 
    e.printStackTrace(); 
   } 
  } 
 
  public void onWindowResize(int width, int height) { 
   //处理surfaceview的大小改变事件 
  } 
 } 
 
} 

Math.toRadians(fishAngle)