public class LoadingDrawable extends Drawable implements Animatable {
    private final LoadingRenderer mLoadingRender;

    private final Callback mCallback = new Callback() {
        @Override
        public void invalidateDrawable(Drawable d) {
            invalidateSelf();
        }

        @Override
        public void scheduleDrawable(Drawable d, Runnable what, long when) {
            scheduleSelf(what, when);
        }

        @Override
        public void unscheduleDrawable(Drawable d, Runnable what) {
            unscheduleSelf(what);
        }
    };

    public LoadingDrawable(LoadingRenderer loadingRender) {
        this.mLoadingRender = loadingRender;
        this.mLoadingRender.setCallback(mCallback);
    }

    @Override
    protected void onBoundsChange(Rect bounds) {
        super.onBoundsChange(bounds);
        this.mLoadingRender.setBounds(bounds);
    }

    @Override
    public void draw(Canvas canvas) {
        if (!getBounds().isEmpty()) {
            this.mLoadingRender.draw(canvas);
        }
    }

    @Override
    public void setAlpha(int alpha) {
        this.mLoadingRender.setAlpha(alpha);
    }

    @Override
    public void setColorFilter(ColorFilter cf) {
        this.mLoadingRender.setColorFilter(cf);
    }

    @Override
    public int getOpacity() {
        return PixelFormat.TRANSLUCENT;
    }

    @Override
    public void start() {
        this.mLoadingRender.start();
    }

    @Override
    public void stop() {
        this.mLoadingRender.stop();
    }

    @Override
    public boolean isRunning() {
        return this.mLoadingRender.isRunning();
    }

    @Override
    public int getIntrinsicHeight() {
        return (int) this.mLoadingRender.mHeight;
    }

    @Override
    public int getIntrinsicWidth() {
        return (int) this.mLoadingRender.mWidth;
    }
}

public abstract class LoadingRenderer {
    private static final long ANIMATION_DURATION = 1333;
    private static final float DEFAULT_SIZE = 56.0f;

    private final ValueAnimator.AnimatorUpdateListener mAnimatorUpdateListener
            = new ValueAnimator.AnimatorUpdateListener() {
        @Override
        public void onAnimationUpdate(ValueAnimator animation) {
            computeRender((float) animation.getAnimatedValue());
            invalidateSelf();
        }
    };

    /**
     * Whenever {@link LoadingDrawable} boundary changes mBounds will be updated.
     * More details you can see {@link LoadingDrawable#onBoundsChange(Rect)}
     */
    protected final Rect mBounds = new Rect();

    private Drawable.Callback mCallback;
    private ValueAnimator mRenderAnimator;

    protected long mDuration;

    protected float mWidth;
    protected float mHeight;

    public LoadingRenderer(Context context) {
        initParams(context);
        setupAnimators();
    }

    @Deprecated
    protected void draw(Canvas canvas, Rect bounds) {
    }

    protected void draw(Canvas canvas) {
        draw(canvas, mBounds);
    }

    protected abstract void computeRender(float renderProgress);

    protected abstract void setAlpha(int alpha);

    protected abstract void setColorFilter(ColorFilter cf);

    protected abstract void reset();

    protected void addRenderListener(Animator.AnimatorListener animatorListener) {
        mRenderAnimator.addListener(animatorListener);
    }

    void start() {
        reset();
        mRenderAnimator.addUpdateListener(mAnimatorUpdateListener);

        mRenderAnimator.setRepeatCount(ValueAnimator.INFINITE);
        mRenderAnimator.setDuration(mDuration);
        mRenderAnimator.start();
    }

    void stop() {
        // if I just call mRenderAnimator.end(),
        // it will always call the method onAnimationUpdate(ValueAnimator animation)
        // why ? if you know why please send email to me (dinus_developer@163.com)
        mRenderAnimator.removeUpdateListener(mAnimatorUpdateListener);

        mRenderAnimator.setRepeatCount(0);
        mRenderAnimator.setDuration(0);
        mRenderAnimator.end();
    }

    boolean isRunning() {
        return mRenderAnimator.isRunning();
    }

    void setCallback(Drawable.Callback callback) {
        this.mCallback = callback;
    }

    void setBounds(Rect bounds) {
        mBounds.set(bounds);
    }

    private void initParams(Context context) {
        mWidth = DensityUtil.dip2px(context, DEFAULT_SIZE);
        mHeight = DensityUtil.dip2px(context, DEFAULT_SIZE);

        mDuration = ANIMATION_DURATION;
    }

    private void setupAnimators() {
        mRenderAnimator = ValueAnimator.ofFloat(0.0f, 1.0f);
        mRenderAnimator.setRepeatCount(Animation.INFINITE);
        mRenderAnimator.setRepeatMode(Animation.RESTART);
        mRenderAnimator.setDuration(mDuration);
        //fuck you! the default interpolator is AccelerateDecelerateInterpolator
        mRenderAnimator.setInterpolator(new LinearInterpolator());
        mRenderAnimator.addUpdateListener(mAnimatorUpdateListener);
    }

    private void invalidateSelf() {
        mCallback.invalidateDrawable(null);
    }

}