Duplicate page loads

[jonjomckay]

Hello. I occasionally seem to get the first page of results loading twice, and I've narrowed it down to this line of code.

It appears that the method is called twice (as expected, I think), but previousPageKeys isn't yet populated on the second call. The first page key only seems to get added to previousPageKeys after _load is called the second time.

[pmkod]

Hello. I occasionally seem to get the first page of results loading twice, and I've narrowed it down to this line of code.

It appears that the method is called twice (as expected, I think), but previousPageKeys isn't yet populated on the second call. The first page key only seems to get added to previousPageKeys after _load is called the second time.

For me too, the page is reloaded twice, when I leave it and return to it.

[pmkod]

I'm sorry, it was due to poor implementation on my part. In your load function, you check the list of previousKeys using the .contains function. It turns out that I was using a specific type for my keys and I didn't overload the == operator to get a good equality comparison. I used the equatable library for this, and everything works correctly now. Thanks for your library.

[Arjun544]

@pmkod Can you please share some code?

[dJani97]

Same issue here. For some reason, load is called twice so quickly that first call doesn't have time to finish.

For now I solved this using mutex. If another load call is still in progress, then I just return null from the load function:

Here is my implementation:

mutex provider, keyed by the page:

typedef MutexFamily = (int page, int limit);
final mutexProvider = Provider.family<Mutex, MutexFamily>((ref, family) => Mutex());

load:

load: (page, limit) async {
  final mutex = ref.read(mutexProvider((page, limit)));

  if (mutex.isLocked) {
    print('PagedNotifier.load is throttled, returning empty page');
    return await mutex.protect(() async {
      // awaits previous call before returning, to avoid showing `noItemsFoundIndicatorBuilder` for a brief moment.
      // you don't have to put any instructions here, just awaiting .protect() does to job.
    }); 
    return null;
  }

  return mutex.protect(() async {
    final items = // copy your usual async loading logic here
    return items; 
  });
},