GifFrameManager.java

package com.bumptech.glide.load.resource.gif;

import android.content.Context;
import android.graphics.Bitmap;
import android.os.Handler;
import android.os.Looper;
import android.os.SystemClock;
import com.bumptech.glide.Glide;
import com.bumptech.glide.load.ResourceDecoder;
import com.bumptech.glide.load.ResourceEncoder;
import com.bumptech.glide.load.SkipCache;
import com.bumptech.glide.load.Transformation;
import com.bumptech.glide.load.engine.cache.MemorySizeCalculator;
import com.bumptech.glide.load.resource.NullCacheDecoder;
import com.bumptech.glide.load.resource.bitmap.BitmapEncoder;
import com.bumptech.glide.load.resource.bitmap.StreamBitmapDecoder;
import com.bumptech.glide.gifdecoder.GifDecoder;
import com.bumptech.glide.request.target.SimpleTarget;

import java.io.InputStream;

class GifFrameManager {
    // 16ms per frame = 60fps
    static final long MIN_FRAME_DELAY = 16;
    private final MemorySizeCalculator calculator;
    private final GifFrameModelLoader frameLoader;
    private final GifFrameResourceDecoder frameResourceDecoder;
    private final ResourceDecoder<InputStream, Bitmap> cacheDecoder;
    private final GifDecoder decoder;
    private final Handler mainHandler;
    private final ResourceEncoder<Bitmap> encoder;
    private final Context context;

    private Transformation<Bitmap> transformation;
    private DelayTarget current;
    private DelayTarget next;

    public interface FrameCallback {
        public void onFrameRead(Bitmap frame);
    }

    public GifFrameManager(Context context, GifDecoder decoder, Transformation<Bitmap> transformation) {
        this(context, decoder, new Handler(Looper.getMainLooper()), transformation);
    }

    public GifFrameManager(Context context, GifDecoder decoder, Handler mainHandler,
            Transformation<Bitmap> transformation) {
        this.context = context;
        this.decoder = decoder;
        this.mainHandler = mainHandler;
        this.transformation = transformation;
        calculator = new MemorySizeCalculator(context);
        frameLoader = new GifFrameModelLoader();
        frameResourceDecoder = new GifFrameResourceDecoder();

        if (!decoder.isTransparent()) {
            // For non transparent gifs, we can beat the performance of our gif decoder for each frame by decoding jpegs
            // from disk.
            cacheDecoder = new StreamBitmapDecoder(context);
            encoder = new BitmapEncoder(Bitmap.CompressFormat.JPEG, 70);
        } else {
            // For transparent gifs, we would have to encode as pngs which is actually slower than our gif decoder so we
            // avoid writing frames to the disk cache entirely.
            cacheDecoder = NullCacheDecoder.get();
            encoder = SkipCache.get();
        }
    }

    Transformation<Bitmap> getTransformation() {
        return transformation;
    }

    public void getNextFrame(FrameCallback cb) {
        decoder.advance();
        // We don't want to blow out the entire memory cache with frames of gifs, so try to set some
        // maximum size beyond which we will always just decode one frame at a time.
        boolean skipCache = decoder.getDecodedFramesByteSizeSum() > calculator.getMemoryCacheSize() / 2;

        long targetTime = SystemClock.uptimeMillis() + (Math.min(MIN_FRAME_DELAY, decoder.getNextDelay()));
        next = new DelayTarget(decoder, cb, targetTime, mainHandler);

        Glide.with(context)
                .using(frameLoader, GifDecoder.class)
                .load(decoder)
                .as(Bitmap.class)
                .decoder(frameResourceDecoder)
                .cacheDecoder(cacheDecoder)
                .transform(transformation)
                .encoder(encoder)
                .skipMemoryCache(skipCache)
                .into(next);
    }

    public void clear() {
        if (current != null) {
            Glide.clear(current);
            mainHandler.removeCallbacks(current);
        }
        if (next != null) {
            Glide.clear(next);
            mainHandler.removeCallbacks(next);
        }
    }

    class DelayTarget extends SimpleTarget<Bitmap> implements Runnable {
        private FrameCallback cb;
        private long targetTime;
        private Handler mainHandler;
        private Bitmap resource;

        public DelayTarget(GifDecoder decoder, FrameCallback cb, long targetTime, Handler mainHandler) {
            super(decoder.getWidth(), decoder.getHeight());
            this.cb = cb;
            this.targetTime = targetTime;
            this.mainHandler = mainHandler;
        }

        @Override
        public void onResourceReady(final Bitmap resource) {
            this.resource = resource;
            mainHandler.postAtTime(this, targetTime);
            if (current != null) {
                Glide.clear(current);
            }
            current = next;
            next = null;
        }

        @Override
        public void run() {
            cb.onFrameRead(resource);
        }
    }
}