Android create fragment with Arguments not work

Question

I want to create fragment with Arguments,

and refer to this post [ Do fragments really need an empty constructor? ].

But not work, I don't know how to fix it.

Code:

Fragment

public class TestFragment extends Fragment {
  private final static String BUNDLE_TITLE = "title";
  private RelativeLayout rootView;
  private String title = "";

  public static TestFragment newInstance(String titleName){
    Bundle bundle = new Bundle();
    bundle.putString(BUNDLE_TITLE,titleName);
    TestFragment testFragment = new TestFragment();
    testFragment.setArguments(bundle);
    return testFragment;
  }

  @Override
  public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
                         @Nullable Bundle savedInstanceState) {
    if (rootView == null) {
        rootView = (RelativeLayout) inflater.inflate(R.layout.find_mac, container, false);
    }
    return rootView;
  }

  @Override
  public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Bundle data = getArguments();
    if(data != null){
        this.title = getArguments().getString(BUNDLE_TITLE,"");
    }
  }

  String getTitle() {
    return title;
  }
}

And in Activity,

@Override
protected void onStart() {
  super.onStart();
  TestFragment testFragment = TestFragment.newInstance("hello");
  Log.d("debug","get title:"+testFragment.getTitle());
}

The Log show only "get title:",

I can't get the title "hello" word.

Answer 1

This is because when you calling:

TestFragment testFragment = TestFragment.newInstance("hello");
Log.d("debug","get title:"+testFragment.getTitle());

the testFragment fragment is not yet finished created. Because it is an asynchronous process.

So, you need to create a listener in activity to tell that the fragment is created, then in it, you can get the title.

You can read Communicating with Other Fragments for implementing the listener.