code: private void selectImage() {
          // Start picker activity
  
          // For simplicity we're loading credentials from a string res, don't do this in production
          String apiKey = getString(R.string.filestack_api_key);
          if (apiKey.equals("")) {
              throw new RuntimeException("Create a string res value for \"filestack_api_key\"");
          }
  
          Config config = new Config(apiKey, "https://form.samples.android.filestack.com");
          Context context = getContext();
          Intent pickerIntent = new Intent(context, FsActivity.class);
          pickerIntent.putExtra(FsConstants.EXTRA_CONFIG, config);
          // Restrict file selections to just images
          String[] mimeTypes = {"image/*"};
          pickerIntent.putExtra(FsConstants.EXTRA_MIME_TYPES, mimeTypes);
          context.startActivity(pickerIntent);
  
          // Show loading progress spinner
          ((MainActivity) getActivity()).setLoading(true);
      }
docs: Handles user clicking select button, launches the picker UI