帧动画内存OOM与SurfaceView逐帧解析

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我是靠谱客的博主笑点低樱桃，这篇文章主要介绍帧动画内存OOM与SurfaceView逐帧解析，现在分享给大家，希望可以做个参考。

帧动画内存OOM？不存在的！—— SurfaceView逐帧解析- https://juejin.im/post/5ccc1dcbe51d456e8b07ddf4
play frame animation by SurfaceView. Get rid of OOM due to complex frame animation- https://github.com/wisdomtl/FrameSurfaceView/tree/master
Android 提供了AnimationDrawable用于实现帧动画。在动画开始之前，所有帧的图片都被解析并占用内存，一旦动画较复杂帧数较多，在低配置手机上容易发生 OOM。即使不发生 OOM，也会对内存造成不小的压力。

- 原生帧动画AnimationDrawable
AnimationDrawable drawable = new AnimationDrawable();
drawable.addFrame(getDrawable(R.drawable.frame1), frameDuration);
drawable.addFrame(getDrawable(R.drawable.frame2), frameDuration);
drawable.addFrame(getDrawable(R.drawable.frame3), frameDuration);
drawable.addFrame(getDrawable(R.drawable.frame4), frameDuration);
drawable.setOneShot(true);

ImageView ivFrameAnim = ((ImageView) findViewById(R.id.frame_anim));
ivFrameAnim.setImageDrawable(drawable);
drawable.start();

有没有什么办法让帧动画的数据逐帧加载，而不是一次性全部加载到内存？SurfaceView就提供了这种能力。
为了显示一帧，需要经历计算和渲染两个过程，CPU 先计算出这一帧的图像数据并写入内存，然后调用 OpenGL 命令将内存中数据渲染成图像存放在 GPU Buffer 中，显示设备每隔一定时间从 Buffer 中获取图像并显示。

-- SurfaceView逐帧解析，自定义SurfaceView的模版代码：
public abstract class BaseSurfaceView extends SurfaceView implements SurfaceHolder.Callback {
public static final int DEFAULT_FRAME_DURATION_MILLISECOND = 50;
//用于计算帧数据的线程
private HandlerThread handlerThread;
private Handler handler;
//帧刷新频率
private int frameDuration = DEFAULT_FRAME_DURATION_MILLISECOND;
//用于绘制帧的画布
private Canvas canvas;
private boolean isAlive;

public BaseSurfaceView(Context context) {
super(context);
init();
}

protected void init() {
getHolder().addCallback(this);
//设置透明背景，否则SurfaceView背景是黑的
setBackgroundTransparent();
}

private void setBackgroundTransparent() {
getHolder().setFormat(PixelFormat.TRANSLUCENT);
setZOrderOnTop(true);
}

@Override
public void surfaceCreated(SurfaceHolder holder) {
isAlive = true;
startDrawThread();
}

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
stopDrawThread();
isAlive = false;
}

//停止帧绘制线程
private void stopDrawThread() {
handlerThread.quit();
handler = null;
}

//启动帧绘制线程
private void startDrawThread() {
handlerThread = new HandlerThread("SurfaceViewThread");
handlerThread.start();
handler = new Handler(handlerThread.getLooper());
handler.post(new DrawRunnable());
}

private class DrawRunnable implements Runnable {

@Override
public void run() {
if (!isAlive) {
return;
}
try {
//1.获取画布
canvas = getHolder().lockCanvas();
//2.绘制一帧
onFrameDraw(canvas);
} catch (Exception e) {
e.printStackTrace();
} finally {
//3.将帧数据提交
getHolder().unlockCanvasAndPost(canvas);
//4.一帧绘制结束
onFrameDrawFinish();
}
//不停的将自己推送到绘制线程的消息队列以实现帧刷新
handler.postDelayed(this, frameDuration);
}
}

protected abstract void onFrameDrawFinish();

protected abstract void onFrameDraw(Canvas canvas);
}

- 逐帧解析 & 及时回收
public class FrameSurfaceView extends BaseSurfaceView {
public static final int INVALID_BITMAP_INDEX = Integer.MAX_VALUE;
private List<Integer> bitmaps = new ArrayList<>();
private Bitmap frameBitmap;
private int bitmapIndex = INVALID_BITMAP_INDEX;
private Paint paint = new Paint();
private BitmapFactory.Options options;
private Rect srcRect;
private Rect dstRect = new Rect();

public void setDuration(int duration) {
int frameDuration = duration / bitmaps.size();
setFrameDuration(frameDuration);
}

public void setBitmaps(List<Integer> bitmaps) {
if (bitmaps == null || bitmaps.size() == 0) {
return;
}
this.bitmaps = bitmaps;
getBitmapDimension(bitmaps.get(0));
}

private void getBitmapDimension(Integer integer) {
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeResource(this.getResources(), integer, options);
defaultWidth = options.outWidth;
defaultHeight = options.outHeight;
srcRect = new Rect(0, 0, defaultWidth, defaultHeight);;
}

public FrameSurfaceView(Context context) {
super(context);
}

@Override
protected void init() {
super.init();
//定义解析Bitmap参数为可变类型，这样才能复用Bitmap
options = new BitmapFactory.Options();
options.inMutable = true;
}

@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
super.onLayout(changed, left, top, right, bottom);
dstRect.set(0, 0, getWidth(), getHeight());
}

@Override
protected int getDefaultWidth() {
return defaultWidth;
}

@Override
protected int getDefaultHeight() {
return defaultHeight;
}

@Override
protected void onFrameDrawFinish() {
//每帧绘制完毕后不再回收
// recycle();
}

public void recycle() {
if (frameBitmap != null) {
frameBitmap.recycle();
frameBitmap = null;
}
}

@Override
protected void onFrameDraw(Canvas canvas) {
clearCanvas(canvas);
if (!isStart()) {
return;
}
if (!isFinish()) {
drawOneFrame(canvas);
} else {
onFrameAnimationEnd();
}
}

private void drawOneFrame(Canvas canvas) {
frameBitmap = BitmapUtil.decodeOriginBitmap(getResources(),
//复用上一帧Bitmap的内存
bitmaps.get(bitmapIndex), options);
options.inBitmap = frameBitmap;
canvas.drawBitmap(frameBitmap, srcRect, dstRect, paint);
bitmapIndex++;
}

private void onFrameAnimationEnd() {
reset();
}

private void reset() {
bitmapIndex = INVALID_BITMAP_INDEX;
}

private boolean isFinish() {
return bitmapIndex >= bitmaps.size();
}

private boolean isStart() {
return bitmapIndex != INVALID_BITMAP_INDEX;
}

public void start() {
bitmapIndex = 0;
}

private void clearCanvas(Canvas canvas) {
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
canvas.drawPaint(paint);
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC));
}
}