In my app, I am trying to decode bitmaps Asynchronously, therefore I am using CompletableFuture.runAsync(() -> {}); method to run it Asynchronously, but it seems bitmap decoding is still not running Asynchronously because I am having a lagging in my UIs every time I run my app (I am running spinKitLayout to indicate the user, process is still going on, but spinKitLayout is the one which is lagging in my main thread), I don’t understand why it is still having a lag although I am running it Asynchronously. I am still a newbie to Asynchronous programming, Can anyone point me out where the problem is in my code and what can be the possible solution to this?

private void createBitmapDatabase() {
    currentBitmapIndex = 0;
    createNextBitMapFile(bitmapDataList);
}

private void createNextBitMapFile(List<BitmapData> bitmapDataList) {
    if (currentBitmapIndex < bitmapDataList.size()){
        CompletableFuture.runAsync(() -> {
            createBitmapAsync(bitmapDataList.get(currentBitmapIndex).getBitmapUri(),bitmapDataList.get(currentBitmapIndex).getBitmapName(),currentBitmapIndex, new BitmapCreationListener() {
                @Override
                public void onBitmapCreated(int index, String bitmapName, Bitmap bitmap) {
                    runOnUiThread(() -> {
                        augmentedImageDatabase.addImage(bitmapName,bitmap);
                        currentBitmapIndex++;
                        createNextBitMapFile(bitmapDataList);
                    });
                }

                @Override
                public void onBitmapCreationFailed(int index, String bitmapName, String errorMessage) {
                    runOnUiThread(() -> {
                        Toast.makeText(MainActivity.this, "Bitmap for "+bitmapName+" "+errorMessage, Toast.LENGTH_SHORT).show();
                        bitmapFailedCount++;
                        currentBitmapIndex++;
                        createNextBitMapFile(bitmapDataList);
                    });
                }
            });
        });
    }else {
        if (bitmapFailedCount != 0){
            runOnUiThread(() -> Toast.makeText(this, bitmapDataList.size()-bitmapFailedCount+" bitmaps created and "+bitmapFailedCount+" Failed!", Toast.LENGTH_SHORT).show());
        }else {
            runOnUiThread(() -> Toast.makeText(this, "All bitmaps created", Toast.LENGTH_SHORT).show());
        }

        backgroundBlurView.setVisibility(View.GONE);
        spinKitLayout.setVisibility(View.GONE);

        if (augmentedImageDatabase != null){
            Toast.makeText(this, "Database created with "+augmentedImageDatabase.getNumImages()+" images", Toast.LENGTH_SHORT).show();
        }else {
            Toast.makeText(this, "Database is Empty", Toast.LENGTH_SHORT).show();
        }
    }
}

private void createBitmapAsync(Uri bitmapUri,String bitmapName, int index, BitmapCreationListener bitmapCreationListener) {
    //CompletableFuture.runAsync(() -> {
        try (InputStream inputStream = getContentResolver().openInputStream(bitmapUri)) {
            Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
            if (bitmap != null) {
                bitmapCreationListener.onBitmapCreated(index, bitmapName, bitmap);
            } else {
                bitmapCreationListener.onBitmapCreationFailed(index, bitmapName, "Failed to decode bitmap!");
            }
        } catch (IOException e) {
            bitmapCreationListener.onBitmapCreationFailed(index, bitmapName, "Error loading bitmap: " + e.getMessage());
        }
    //});
}