Brtdku

I am downloading multiple files using FirebaseStorage. The task to download the files is inside a WHILE loop. The WHILE loop is inside another FOR loop. The problem is that I want the WHILE loop to move forward only when all downloads are complete. I tried using Tasks.await(task) but it doesn't seem to work. Could you guys help me with that?

For (DataSnapshot ds: datasnapshot.getChildren()){

    ...

    while (i[0] < imgs.length) {

        Task<Uri> task = mStorageReference.child(uid).child("notes").child(imgname).getDownloadUrl().addOnCompleteListener(new OnCompleteListener<Uri>() {

            @Override

            public void onComplete(@NonNull Task<Uri> task) {

                if (task.isSuccessful()) {

                    ...

                });

        try {

             Tasks.await(task);

        } catch (ExecutionException e) {

            e.printStackTrace();

        } catch (InterruptedException e) {

            e.printStackTrace();

        }

        i[0]++;

        }

    }

I also tried using i[0]++ inside the storage task, but the loop just freezes.

Calling Task.await() on Android is a recipe for problems, as even if it works, it will actually block the main thread. Are you sure you're not looking for Task.whenAllComplete(), which returns a Task that completes when all getDownloadUrl tasks complete.

Implementing it would look something like this:

List<Task<Uri>> downloadUrlTasks = new LinkedList<Task<Uri>>();



while (i[0] < imgs.length) {

    Task<Uri> task = mStorageReference.child(uid).child("notes").child(imgname).getDownloadUrl();

    downloadUrlTasks.add(task);

    i[0]++;

}



try {

     Tasks.whenAllComplete(downloadUrlTasks).addOnCompleteListener(new OnCompleteListener<List<Task<Uri>>() {

         @Override

         public void onComplete(@NonNull List<Task<Uri>> tasks) {

             // All tasks have completed, now you can get all download URLs by looping over the tasks

         }

     });

} catch (ExecutionException e) {

    e.printStackTrace();

} catch (InterruptedException e) {

    e.printStackTrace();

}

Even simpler: if you only want to process the download URLs if all of them were successfully gotten from the server, you can use Tasks. whenAllSuccess:

 Tasks.whenAllSuccess(downloadUrlTasks).addOnSuccessListener(new OnSuccessListener<List<Uri>() {

     @Override

     public void onSuccess(@NonNull List<Uri> uris) {

         // All tasks have succeeded, the uris list contains all download URLs

     }

 });