onCreateView is not being called Android

Question

I have an activity that is called by the MainActivity. It was pre made by Android Studio for me.

public class DetailActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_detail);   
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.detail, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

And I got this Fragment that also was auto-generated but with a few changes.

public class DetailActivityFragment extends Fragment {

    public DetailActivityFragment() {
    }

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

        Intent intent = getActivity().getIntent();
        View rootView = inflater.inflate(R.layout.fragment_detail, container, false);

        if(intent != null && intent.hasExtra(Intent.EXTRA_TEXT)){
            String forecastStr = intent.getStringExtra(Intent.EXTRA_TEXT);
            TextView textView = (TextView) rootView.findViewById(R.id.detail_text);
            textView.setText(forecastStr);
        }
        return rootView;
    }
}

But the onCreateView method doesn't even execute. How can I run it?

Here is the fragment_detail.xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="app.com.example.android.sunshine.DetailActivityFragment">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

</RelativeLayout>

And here is the activity_detail.xml:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.android.sunshine.app.DetailActivity"
tools:ignore="MergeRootFrame">

<TextView
    android:id="@+id/detail_text"
    android:text="Example"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    />

</FrameLayout>

Answer 1

In your post you did not show where you create the fragment, just in case you did not do that, here is an example:

DetailActivityFragment fragment = new DetailActivityFragment();
if (fragment != null) {
    FragmentManager fragmentManager = getFragmentManager();
    fragmentManager.beginTransaction()
            .replace(R.id.frame_container, fragment).commit();
} else {
    // error in creating fragment
    Log.e(LOG_TAG, "Error in creating fragment");
}