How to add “UP” back button in fragment in Android

<android.support.v7.widget.Toolbar
            android:id="@+id/toolbarId"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            app:navigationIcon="?attr/homeAsUpIndicator"/>

 <android.support.v7.widget.Toolbar
            android:id="@+id/toolbarId"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            app:navigationIcon="?attr/homeAsUpIndicator"/>

Toolbar toolbar = (ToolBar) getActivity().findViewById(R.id.toolbarId);

toolbar.setNavigationOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            getActivity().onBackPressed();
        }
    });