将图标添加到片段actionbar并获取对它的引用

<androidx.appcompat.widget.Toolbar
    android:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="?attr/actionBarSize"
    android:background="?attr/colorPrimary"
    android:elevation="4dp"
    android:theme="@style/ThemeOverlay.AppCompat.ActionBar"
    app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_layout, container, false);

    Toolbar toolbar = view.findViewById(R.id.toolbar);
    AppCompatActivity activity = (AppCompatActivity) getActivity();
    activity.setSupportActionBar(toolbar);

    return view;
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

    ActionBar actionBar = ((AppCompatActivity) getActivity()).getSupportActionBar();
    if (actionBar != null) {
        actionBar.setDisplayHomeAsUpEnabled(true);
        actionBar.setHomeAsUpIndicator(R.drawable.ic_menu);
    }
}