Scrolling animation in NavigationView

Question

My activity has a NavigationView inside a DrawerLayout.

When user clicks on a button in the NavigationView header, I would like to scroll to top the DrawerLayout/NavigationView with an animation.

It seems that NavigationView and DrawerLayout don't provide a method to get the actual scroll position (getScrollY() and getScrollX() always return 0) and so I can't do that.

How can I scroll to top with an animation?

<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     android:id="@+id/drawer_layout"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:fitsSystemWindows="true">

     <!-- My content -->

     <android.support.design.widget.NavigationView
         android:id="@+id/navigation"
         android:layout_width="wrap_content"
         android:layout_height="match_parent"
         android:layout_gravity="start"
         app:headerLayout="@layout/navigation_view_header"
         app:menu="@menu/my_navigation_items" />
 </android.support.v4.widget.DrawerLayout>

Answer 1

you need to scroll the NavigationMenuView.

In the below code, it will scroll to top when click on any item in menu

 NavigationView navigationView;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);
}

@Override
public boolean onNavigationItemSelected(MenuItem item) {
        //here will scroll to top
((NavigationMenuView)navigationView.getChildAt(0)).smoothScrollToPosition(0);

        return true;
    }

EDIT: If you want to protect against possible changes down the road, you can use reflection here, like so:

// try to scroll to the top of the navigation menu, if possible
if (navigationView.getChildCount() > 0) {
    View childView = navigationView.getChildAt(0);
    try {
        Method scroll = childView.getClass().getMethod("smoothScrollToPosition", int.class);
        scroll.invoke(childView, 0);
    } catch (NoSuchMethodException |
            SecurityException |
            IllegalAccessException |
            InvocationTargetException e) {
        Log.d(TAG, "smoothScrollToPosition", e);
    }
}