===更新2019年10月30日===
由于我们有新的组件，例如ViewModel和LiveData，因此可以使用ViewModel和Live Data通过一种不同/更简便的方式从Fragment更新活动标题
活动
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
})
} }
主片段
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")
} }
和MainModelView：
class MainViewModel : ViewModel() {
private val _title = MutableLiveData<String>()
val title: LiveData<String>
get() = _title
fun updateActionBarTitle(title: String) = _title.postValue(title) }
然后您可以使用来更新Fragment中的Activity标题 viewModel.updateActionBarTitle("Custom Title From Fragment")
===更新2015年4月10日===
您应该使用侦听器更新操作栏标题
分段：
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);
}
}
和活动：
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);
}
}
在此处阅读更多信息：https : //developer.android.com/training/basics/fragments/communicating.html