Attempt to invoke virtual method 'int java.nio.ByteBuffer.capacity()' on a null object reference

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Issue Info

Info	Value
Device Info
System Version
APNG4Android Library Version	3.0.1
Repro rate	sometimes
Repro with our demo project
Demo project link

Issue Description and Steps

Glide Library Version: 4.16.0
APNG4Android Library Version: 3.0.1

Error Log:

com.github.penfeizhou.animation.decode.FrameSeqDecoder.getMemorySize(FrameSeqDecoder.java:578)
com.github.penfeizhou.animation.FrameAnimationDrawable.getMemorySize(FrameAnimationDrawable.java:301)
com.github.penfeizhou.animation.glide.FrameDrawableTranscoder$1.getSize(FrameDrawableTranscoder.java:48)
com.bumptech.glide.load.engine.EngineResource.getSize(EngineResource.java:62)
com.bumptech.glide.load.engine.cache.LruResourceCache.getSize(LruResourceCache.java:40)
com.bumptech.glide.load.engine.cache.LruResourceCache.getSize(LruResourceCache.java:11)
com.bumptech.glide.util.LruCache.put(LruCache.java:131)
com.bumptech.glide.load.engine.cache.LruResourceCache.put(LruResourceCache.java:11)
com.bumptech.glide.load.engine.Engine.onResourceReleased(Engine.java:401)
com.bumptech.glide.load.engine.EngineResource.release(EngineResource.java:116)
com.bumptech.glide.load.engine.Engine.release(Engine.java:367)
com.bumptech.glide.request.SingleRequest.clear(SingleRequest.java:345)
com.bumptech.glide.manager.RequestTracker.clearAndRemove(RequestTracker.java:70)
com.bumptech.glide.RequestManager.untrack(RequestManager.java:677)
com.bumptech.glide.RequestManager.untrackOrDelegate(RequestManager.java:645)
com.bumptech.glide.RequestManager.clear(RequestManager.java:641)
com.bumptech.glide.RequestBuilder.into(RequestBuilder.java:856)
com.bumptech.glide.RequestBuilder.into(RequestBuilder.java:917)

exception：Attempt to invoke virtual method 'int java.nio.ByteBuffer.capacity()' on a null object reference

I just write code Glide.with(context).load(imageUrl).into(imageView).

In FrameSeqDecoder.java,

public int getMemorySize() {
    synchronized (cacheBitmapsLock) {
        int size = 0;
        for (Bitmap bitmap : cacheBitmaps) {
            if (bitmap.isRecycled()) {
                continue;
            }
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
                size += bitmap.getAllocationByteCount();
            } else {
                size += bitmap.getByteCount();
            }
        }
        if (frameBuffer != null) {
            size += frameBuffer.capacity();
        }
        return size;
    }
}

call capacity() after check frameBuffer is null.

But my project occurs error at there...
Sooo weird...

So I think... the frameBuffer check null in synchronized block, but it reassigned to null outside of the synchronized block/method and then it call capacity(), which causes a null error.

I think you need to fix the frameBuffer to reassigned it within a synchronized block.