使用SurfaceView实现动画

与自定义view绘图进行对比：

1.view绘图没有双缓冲机制，而surfaceview有

2.view绘图更新时，要全部更新整张图片，而surfaceview可以更新部分区域

3.新线程无法直接更新view绘图，需要handler配合。

鱼儿游动的动画:

<?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
        }
    }

}

位置计算图片解释如下:

Math.toRadians(fishAngle)

先理解这句代码的意思:将0-360的角度制角度转化为pi弧度制角度

鱼儿不停的游动，坐标改变其实就是：

当前的x坐标 - 速度*cos角度 ， 当前的y坐标 - 速度*sin角度