Setting Custom ActionBar Title from Fragment

Question

In my Main FragmentActivity, I setup my custom ActionBar title like this:

    LayoutInflater inflator = (LayoutInflater) this             .getSystemService(Context.LAYOUT_INFLATER_SERVICE);     View v = inflator.inflate(R.layout.custom_titlebar, null);      TextView tv = (TextView) v.findViewById(R.id.title);     Typeface tf = Typeface.createFromAsset(this.getAssets(),             "fonts/capsuula.ttf");     tv.setTypeface(tf);     tv.setText(this.getTitle());      actionBar.setCustomView(v); 

This works perfect. However, once I open other Fragments, I want the title to change. I am not sure how to access the Main Activity to do this? In the past, I did this:

((MainFragmentActivity) getActivity()).getSupportActionBar().setTitle(             catTitle); 

Can someone advise on the proper method?

XML:

<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"     android:layout_width="match_parent"     android:layout_height="match_parent"     android:background="@android:color/transparent" >      <TextView         android:id="@+id/title"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:layout_centerVertical="true"         android:layout_marginLeft="5dp"         android:ellipsize="end"         android:maxLines="1"         android:text=""         android:textColor="#fff"         android:textSize="25sp" />  </RelativeLayout> 

Answer 1

What you're doing is correct. Fragments don't have access to the ActionBar APIs, so you have to call getActivity. Unless your Fragment is a static inner class, in which case you should create a WeakReference to the parent and call Activity.getActionBar from there.

To set the title for your ActionBar, while using a custom layout, in your Fragment you'll need to call getActivity().setTitle(YOUR_TITLE).

The reason you call setTitle is because you're calling getTitle as the title of your ActionBar. getTitle returns the title for that Activity.

If you don't want to get call getTitle, then you'll need to create a public method that sets the text of your TextView in the Activity that hosts the Fragment.

In your Activity:

public void setActionBarTitle(String title){     YOUR_CUSTOM_ACTION_BAR_TITLE.setText(title); } 

In your Fragment:

((MainFragmentActivity) getActivity()).setActionBarTitle(YOUR_TITLE); 

Docs:

Activity.getTitle

Activity.setTitle

Also, you don't need to call this.whatever in the code you provided, just a tip.

Answer 2

===Update October, 30, 2019===

Since we have new components such as ViewModel and LiveData, we can have a different/easier way to update Activity Title from Fragment by using ViewModel and Live Data

Activity

class MainActivity : AppCompatActivity() { private lateinit var viewModel: MainViewModel override fun onCreate(savedInstanceState: Bundle?) {     super.onCreate(savedInstanceState)     setContentView(R.layout.main_activity)     if (savedInstanceState == null) {         supportFragmentManager.beginTransaction()             .replace(R.id.container, MainFragment.newInstance())             .commitNow()     }     viewModel = ViewModelProviders.of(this).get(MainViewModel::class.java)     viewModel.title.observe(this, Observer {         supportActionBar?.title = it     }) } } 

MainFragment

class MainFragment : Fragment() { companion object {     fun newInstance() = MainFragment() } private lateinit var viewModel: MainViewModel override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,                           savedInstanceState: Bundle?): View {     return inflater.inflate(R.layout.main_fragment, container, false) } override fun onActivityCreated(savedInstanceState: Bundle?) {     super.onActivityCreated(savedInstanceState)     activity?.run {         viewModel = ViewModelProviders.of(this).get(MainViewModel::class.java)     } ?: throw Throwable("invalid activity")     viewModel.updateActionBarTitle("Custom Title From Fragment") } } 

And MainModelView:

class MainViewModel : ViewModel() { private val _title = MutableLiveData<String>() val title: LiveData<String> get() = _title fun updateActionBarTitle(title: String) = _title.postValue(title) } 

And then you can update the Activity title from Fragment using viewModel.updateActionBarTitle("Custom Title From Fragment")

===Update April, 10, 2015===

You should use listener to update your action bar title

Fragment:

public class UpdateActionBarTitleFragment extends Fragment {     private OnFragmentInteractionListener mListener;      public UpdateActionBarTitleFragment() {     }      @Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         if (getArguments() != null) {         }     }      @Override     public View onCreateView(LayoutInflater inflater, ViewGroup container,                              Bundle savedInstanceState) {         if (mListener != null) {             mListener.onFragmentInteraction("Custom Title");         }         return inflater.inflate(R.layout.fragment_update_action_bar_title2, container, false);     }      @Override     public void onAttach(Activity activity) {         super.onAttach(activity);         try {             mListener = (OnFragmentInteractionListener) activity;         } catch (ClassCastException e) {             throw new ClassCastException(activity.toString()                     + " must implement OnFragmentInteractionListener");         }     }      @Override     public void onDetach() {         super.onDetach();         mListener = null;     }      public interface OnFragmentInteractionListener {         public void onFragmentInteraction(String title);     } } 

And Activity:

public class UpdateActionBarTitleActivity extends ActionBarActivity implements UpdateActionBarTitleFragment.OnFragmentInteractionListener {      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_update_action_bar_title);     }      @Override     public void onFragmentInteraction(String title) {         getSupportActionBar().setTitle(title);     } } 

Read more here: https://developer.android.com/training/basics/fragments/communicating.html