'Frame.frameDuration' is null

New Issue Checklist

• I have searched for a similar issue in the project and found none

Issue Info

Info	Value
Device Info	Redmi Note 7 Pro
System Version	10.0
APNG4Android Library Version	2.23.0
Repro rate	(100%)
Repro with our demo project	-
Demo project link	-

Issue Description and Steps

Although the first frame is saved as file properly. But the frameCount is 0 and cannot get Frame.frameDuration for first frame at least.

I wanted to iterate through each frame but framecount is 0 so stuck here.

Exception: Attempt to read from field 'int com.github.penfeizhou.animation.decode.Frame.frameDuration' on a null object reference

WebPDecoder decoder = new WebPDecoder(new FileLoader(path),null);

  if (decoder != null){

    Bitmap bm = decoder.getFrameBitmap(0);
    // saveBitmap(bm);
    // first frame is saved succefully...

    // but here getFrameCount is 0 and invoking getFrame() causes error 
    int frameCount = decoder.getFrameCount();
    int frameDuration = decoder.getFrame(0).frameDuration;
  }        

also tried this way. But still zero frame count and null getFrame()

FrameSeqDecoder decoder = WebPDrawable.fromFile(path).getFrameSeqDecoder();

WebPDecoder decoder = WebPDrawable.fromFile(path).getFrameSeqDecoder();

[penfeizhou]

The render listener‘s timing is precise.

[CrackerKSR]

The render listener‘s timing is precise.

Is there synchronised way. Because I can’t get Frame Bitmap and and Frame info togather. Either I will get frame count in OnStart() or get Bitmaps outside of render listener.

I tried invoking decoder.stop in OnStart like this

... 
OnStart()
  int count = decoder.getFramesCount();
  decoder.stop();
  while(i<count) {
        Bitmap bm = getFrameBitmap(i);
        i++;
  } 
... 

But this is very slow for large number of frames. Takes 1 second for each iteration