How to get access to list of files from /storage/emulated/0

I'm writing an Android application, which can capture and watch photos. All captured images appear in grid RecyclerView (CameraActivity), where I made all elements are clickable. To store images I'm using internal memory within getExternalFilesDir(Environment.DIRECTORY_PICTURES), because I want to make them accessible only from my application. In the result the full path of my picture folder is /storage/emulated/0/Android/data/com._,_/files/Pictures/image gallery. In the second activity of my app I want to slide between images and for this I need to get the list of image paths from above storage directory. But my problem is that I don't know how to do this. I've tried to use getDir("image gallery", 0) but it simply creates a new folder with path /data/data/com.webartil.cameraapp/app_image gallery. So I need your help to solve my problem. CameraActivity

public class CameraActivity extends AppCompatActivity implements ImageAdapter.OnImageClickListener {

private static final int ACTIVITY_START_CAMERA_APP = 0;
public static final String PATH = "PATH";
private String GALLERY_LOCATION = "image gallery";
private File mGalleryFolder;
private RecyclerView mRecyclerView;
private ImageAdapter imageAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_camera);
    createImageGallery();
    Toolbar toolbar = findViewById(R.id.toolbar_activity_camera);
    setSupportActionBar(toolbar);
    initRecyclerView();
    FloatingActionButton fab = findViewById(R.id.fab_shoot_photo);
    fab.setOnClickListener(view -> takePhoto());
}

private void initRecyclerView() {
    mRecyclerView = findViewById(R.id.gallery_recycler_view);
    RecyclerView.LayoutManager layoutManager = new GridLayoutManager(this, 3);
    mRecyclerView.setLayoutManager(layoutManager);
    imageAdapter = new ImageAdapter(this, mGalleryFolder, this);
    mRecyclerView.setAdapter(imageAdapter);
}

public void takePhoto() {
    Intent callCameraApplicationIntent = new Intent();
    callCameraApplicationIntent.setAction(MediaStore.ACTION_IMAGE_CAPTURE);
    File photoFile = null;
    try {
        photoFile = createImageFile();
    } catch (IOException e) {
        e.printStackTrace();
    }
    callCameraApplicationIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(photoFile));
    startActivityForResult(callCameraApplicationIntent, ACTIVITY_START_CAMERA_APP);
}

@Override
protected void onActivityResult(final int requestCode, final int resultCode, final Intent data) {
    RecyclerView.Adapter newImageAdapter = new ImageAdapter(this, mGalleryFolder, this);
    mRecyclerView.swapAdapter(newImageAdapter, false);
}

File createImageFile() throws IOException {
    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
    String imageFileName = "IMAGE_" + timeStamp + "_";
    return File.createTempFile(imageFileName,".jpg", mGalleryFolder);
}

private void createImageGallery() {
    mGalleryFolder =
            new File(getApplicationContext().getExternalFilesDir(Environment.DIRECTORY_PICTURES),
                    GALLERY_LOCATION);
    if(!mGalleryFolder.exists()) {
        mGalleryFolder.mkdirs();
    }
    Log.d(PATH, mGalleryFolder.getAbsolutePath());
}

@Override
public void onClickImage(final View view, final int position) {
    Intent intent = new Intent(this, ImageActivity.class);
    intent.putExtra(PATH, position);
    startActivity(intent);
}
}

First: mentioned directory path is accessible for all apps.

Second: listings can be done with new File(path).listFiles();