Whitespace below CoordinatorLayout in DrawerLayout

Question

I am trying to implement a layout with a CollapsingToolbarLayout inside a DrawerLayout. The whole acitivty_main.xml looks like this:

<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/activity_main__drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <!-- The CoordinatorLayout is used to coordinate (rly) scroll events between different views -->
    <android.support.design.widget.CoordinatorLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <!-- The AppBar (everything above the scrolling content) -->
        <android.support.design.widget.AppBarLayout
            android:layout_height="wrap_content"
            android:layout_width="match_parent"
            android:id="@+id/activity_main__app_bar"
            android:fitsSystemWindows="true"
            app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

            <android.support.design.widget.CollapsingToolbarLayout
                android:id="@+id/activity_main__collapsing_toolbar"
                android:layout_width="match_parent"
                android:layout_height="@dimen/appbar_size_expanded"
                android:minHeight="?attr/actionBarSize"
                app:expandedTitleMarginEnd="16dp"
                app:expandedTitleMarginStart="72dp"
                app:expandedTitleMarginBottom="32dp"
                app:expandedTitleTextAppearance="@style/ExpandedAppBarTitle"
                app:contentScrim="?attr/colorPrimary"
                app:layout_scrollFlags="scroll|exitUntilCollapsed">

                <android.support.v7.widget.Toolbar
                    android:id="@+id/activity_main__toolbar"
                    android:layout_height="?attr/actionBarSize"
                    android:layout_width="match_parent"
                    android:fitsSystemWindows="true"
                    android:background="?attr/colorPrimary"
                    app:layout_collapseMode="pin"
                    app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />

            </android.support.design.widget.CollapsingToolbarLayout>

        </android.support.design.widget.AppBarLayout>

        <!-- The scrolling content view -->
        <android.support.v4.widget.NestedScrollView
            android:id="@+id/activity_main__content_layout"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:background="#CCC333"
            app:layout_behavior="@string/appbar_scrolling_view_behavior" />

        <!-- The add button -->
        <android.support.design.widget.FloatingActionButton
            android:id="@+id/activity_main__floating_action_button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="16dp"
            android:src="@drawable/ic_add_white_24dp"
            android:clickable="true"
            app:layout_anchor="@+id/activity_main__app_bar"
            app:layout_anchorGravity="bottom|right|end"
            app:borderWidth="0dp"
            app:elevation="@dimen/fab_elevation" />

    </android.support.design.widget.CoordinatorLayout>

    <!-- The navigation drawer -->
    <android.support.design.widget.NavigationView
        android:id="@+id/activity_main__navigation_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:background="@android:color/white"
        app:menu="@menu/menu_drawer"
        app:headerLayout="@layout/drawer_navigation_header" />

</android.support.v4.widget.DrawerLayout>

The layout and app structure is loosely based on this tutorial by codepath, where I have changed the FrameLayout for a NestedScrollView (even though the effect appears with both).

Now the view I intend to use for the actual content has some weird padding (I have used a background color to clarify where it is actually rendered):

Where did I mess up?

Answer 1

Try to remove the : exitUntilCollapsed

Into CollapsingToolbarlayout you have now this code

app:layout_scrollFlags="scroll"

Answer 2

Where did I mess up?

It's Design Library's fault. Layouts "shorter" than screen height cause gaps, misbehaviour in collapsing/unfolding <CollapsingToolbarLayout> (i.e. you need to drag outside of collapsed area to unfold it again etc, etc, etc. It's just quite buggy at the moment or writing this answer (it will, hopefully be fixed some day, but I got no clue when this is going to happen).