Android FragmentTransaction Replace method

Question

I have a problem passing arguments down to the fragment from my main activity. getArguments method returns null but at the same time the fragment displays the arguments I'm trying to pass but in a different position. I'm sure it has to do with the container I'm replacing on the replace method.

My main activity:

public class MainActivity extends AppCompatActivity {

    private final String FRAGMENT_TAG = "fragment_tag";
    public static final String USER_NAME = "userName";
    public static final String USER_PASSWORD = "userPassword";

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

        User user = getIntent().getParcelableExtra(LoginActivityFragment.SERVER_MESSAGE);
        Bundle bundle = new Bundle();
        bundle.putString(USER_NAME, user.getUser_name());
        bundle.putString(USER_PASSWORD, user.getUser_password());

        if (user != null) {
            FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
            MainActivityFragment fragment = (MainActivityFragment) getSupportFragmentManager()
                    .findFragmentByTag(FRAGMENT_TAG);
            if (fragment != null) {
                ft.replace(android.R.id.content, fragment);
                ft.commit();
            } else {
                MainActivityFragment newFragment = new MainActivityFragment();
                ft.replace(android.R.id.content, newFragment, FRAGMENT_TAG);
                newFragment.setArguments(bundle);
                ft.commit();
            }
        }
    }
}

My MainActivityFragment:

public class MainActivityFragment extends Fragment {

    private final String ERROR = "Error";

    public MainActivityFragment() {
    }

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

        View rootView = inflater.inflate(R.layout.fragment_main, container, false);

        TextView username = (TextView) rootView.findViewById(R.id.username_test);
        TextView password = (TextView) rootView.findViewById(R.id.pass_test);

        Bundle bundle = getArguments();
        try {
            username.setText(bundle.getString(MainActivity.USER_NAME));
            password.setText(bundle.getString(MainActivity.USER_PASSWORD));
        } catch (Exception e) {
            Log.e(ERROR, "Error: " + e.getMessage());
        }
        return rootView;
    }
}

MainActivity Layout:

content_main Layout

MainActivityFragment Layout

And here is a screenshot of the emulator when I'm passing testName and testPass as arguments:

PPartisan · Accepted Answer

It looks as though you are loading two Fragments - one static, one dynamic. The static Fragment you declare in xml, and in this one getArguments() will always return null. The dynamic Fragment however should not.

I'd suggest you only use dynamic fragments. Replace:

With

And in your MainActivity, replace any reference to android.R.id.content with R.id.fragment_container

Edit:

By the way, I'd recommend using the newInstance() method to pass arguments to your Fragments as it's more reliable. Add this method declaration to MainActivityFragment:

public static MainActivityFragment newInstance(String userName, String userPassword) {

    Bundle args = new Bundle();
    args.putString(USER_NAME_KEY, userName);
    args.putString(USER_PASSWORD_KEY, userPassword);

    MainActivityFragment frag = new MainActivityFragment();
    frag.setArguments(args);

    return frag;

}

And instead of using new MainActivityFragment() to create a new instance, use MainActivityFragment.newInstance("user_name", "user_password). There's a bit more info on it here

Android FragmentTransaction Replace method

Answers (2)

For "getArgument()" return null issue:

For Layout Issue :

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