Spinner items lost on navigate change in Android Studio

Question

I have created an Android Studio project and i have MainActivity , FirstFragment and SecondFragment . On the FirstFragment I have an spinner element. When the app starts the spinner is filled with values, when I switch from the First to the second Fragment and back, the values are gone.

MainActivity

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.

        PublicCameras Cameras = new PublicCameras();
        //get the spinner from the xml.
        Spinner dropdown = findViewById(R.id.cameraList); // This element loses his values when navigating to SecondFragment and back
        ArrayAdapter<String> adapter = new ArrayAdapter<>(this, android.R.layout.simple_spinner_dropdown_item, Cameras.GetNamesEn());
        dropdown.setAdapter(adapter);
        getMenuInflater().inflate(R.menu.menu_main, menu);

        return true;
    }



    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

FirstFragment

public class FirstFragment extends Fragment {

    @Override
    public View onCreateView(
            LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState
    ) {


        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_first, container, false);
    }

    public void onViewCreated(@NonNull View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);



        view.findViewById(R.id.button_first).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                NavHostFragment.findNavController(FirstFragment.this)
                        .navigate(R.id.action_FirstFragment_to_SecondFragment);
            }
        });
    }
}

SecondFragment

public class SecondFragment extends Fragment {

    @Override
    public View onCreateView(
            LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState
    ) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_second, container, false);
    }

    public void onViewCreated(@NonNull View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        view.findViewById(R.id.button_second).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                NavHostFragment.findNavController(SecondFragment.this)
                        .navigate(R.id.action_SecondFragment_to_FirstFragment);
            }
        });
    }
}

I would like to point out that on rotating the values are being set again because of re-entering the function onCreateOptionsMenu. What is the best practice to keep values on a layout change?

Thank you for your time !

Answer 1

You're getting this issue cause when you move from one fragment to other android destorys the fragment and recreates that fragment when returned back this happens in the screen orientation case too. In order to handle this override OnSavedInstance method in you're code

There is a little hack you can make it work.

first override

@Override
public void onSaveInstanceState(@NonNull Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putStringArray("YOUR_KEY", "YOUR_OBJECT");//chnage this with you're object name
}

Now in you're onViewCreated use the SavedInstance variable and get that stringArray using the key and pass this to the spinner.

Try this and if you faced any issue do comment.