Fresco prefetch multiple pictures,How to listen progress? -

i try user datasource<void> datasource datasource.getprogress(),but getprogress() return 0.0,log print once. so,what do?

when obtain datasource imagepipeline, need subscribe it. of explained in fresco documentation.

datasubscriber<t> datasubscriber =         new basedatasubscriber<t>() {           @override           public void onnewresultimpl(datasource<t> datasource) {             ...           }           @override           public void onfailureimpl(datasource<t> datasource) {             ...           }           @override           public void onprogressupdate(datasource<t> datasource) {             float progress = datasource.getprogress();           }         };     mdatasource.subscribe(datasubscriber, muithreadimmediateexecutor);