Accessing non-static variables from another class?

I'm developing an Android app for gender recognition.

Now I want to access the classification result saved as a non-static String, public String GENDER, in public class Camera2BasicFragment extends Fragment implements FragmentCompat.OnRequestPermissionsResultCallback. I want to access it from MainActivity class.

I have a classification method in my Camera2BasicFragment class.

private void classifyFrame() {
    if (gclassifier == null || eclassifier == null || getActivity() == null || cameraDevice == null) {
      showToast("Uninitialized Classifier or invalid context.");
      return;
    }
    Bitmap bitmap_g =
        textureView.getBitmap(GenderClassifier.DIM_IMG_SIZE_X, GenderClassifier.DIM_IMG_SIZE_Y);
    Bitmap bitmap_e =
            textureView.getBitmap(EmotionClassifier.DIM_IMG_SIZE_X, EmotionClassifier.DIM_IMG_SIZE_Y);
    GENDER = gclassifier.classifyFrame(bitmap_g);
    EMOTION = eclassifier.classifyFrame(bitmap_e);
    String textToShow =  GENDER + EMOTION;
    bitmap_g.recycle();
    bitmap_e.recycle();
    showToast(textToShow);
  }

When I access the variable from MainActivity as follows, it gives me a NullPointerException.

if (Camera2BasicFragment.newInstance().GENDER.equals("female")) {
      speech = dialogs.greetings.get("female_senior_happiness");
    }

I tried to use a getter method in Camera2BasicFragment class as follows.

public Bitmap bitmap_g; // Passes the bitmap for gender classification. 
public String classifyGender(Bitmap bitmap) {
    return gclassifier.classifyFrame(bitmap);
  }

However, the passed-in bitmap variable is also null.

I know this sounds like a common problem, but I'm a little bit clueless. Really appreciate any help. Thanks in advance!

Edit: Update codes in MainActiivty.

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_camera);
    if (null == savedInstanceState) {
      getFragmentManager()
              .beginTransaction()
              .replace(R.id.container, Camera2BasicFragment.newInstance())
              .commit();
    }
    mRobotAPI = new RobotAPI(this, robotCallback);
    dialogs = new Dialogs();

    //Initial speech config
    speakConfig.timeout(30);
    speakConfig.volume(60);
    speakConfig.languageId(DialogSystem.LANGUAGE_ID_ZH_TW);
    speakConfig.alwaysListenState(SpeakConfig.MODE_FOREVER);
  }

  //public String gender = Camera2BasicFragment.newInstance().classifyGender(Camera2BasicFragment.newInstance().bitmap_g);
  //public String emotion = Camera2BasicFragment.newInstance().EMOTION;

  public void sayWithExpression(){
    String speech = "Hello World";
    if (Camera2BasicFragment.GENDER.equals("female")) {
      speech = dialogs.greetings.get("female_senior_happiness");
    }

    Log.d(TAG, "say /w ex " + speech);

    //In debugging mode we ignore this for efficiency
    //mRobotAPI.robot.setExpression(generate_expression(speech));
    mRobotAPI.robot.setExpression(RobotFace.HAPPY);
    mRobotAPI.robot.speak(speech, speakConfig);
  }

  @Override
  protected void onResume() {
    super.onResume();
    mRobotAPI.robot.registerListenCallback(robotListenCallback);
    sayWithExpression();
  }

...

Camera2BasicFragment.GENDER -> looks like you have made GENDER variable as static, you can make it non-static and should have a member variable in your MainActivity, i.e,

Camera2BasicFragment fragment = Camera2BasicFragment.newInstance();

then use this fragment in your MainActivity's onCreate and onResume (i.e, in sayWithExpression method)