Stopping a FAB from changing its size

Question

I've anchored a floating action button to a collapsing toolbar. When my activity starts my FAB is a normal size and anchored to the bottom right.

When I collapse the toolbar the FAB disappears.

I'd prefer to keep the FAB and not have it disappear when the toolbar collapses. I'm not sure how to do this. Can anyone help me with how to do that?

My layout:

 <android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/background_light"
    android:fitsSystemWindows="true">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/main.appbar"
        android:layout_width="match_parent"
        android:layout_height="300dp"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
        android:fitsSystemWindows="true"
        >
        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/main_collapsing"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_scrollFlags="scroll|exitUntilCollapsed"
            app:contentScrim="?attr/colorPrimary"
            >

            <ImageView
                android:id="@+id/photo"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:scaleType="centerCrop"
                android:fitsSystemWindows="true"
                app:layout_collapseMode="parallax"
                />

            <android.support.v7.widget.Toolbar
                android:id="@+id/main.toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
                app:layout_collapseMode="pin"
                />
        </android.support.design.widget.CollapsingToolbarLayout>
    </android.support.design.widget.AppBarLayout>

    <android.support.v4.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"
        >

        <TextView
            android:id="@+id/article_body"
            style="?android:attr/textAppearanceMedium"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:padding="16dp"
            android:textSize="20sp"
            android:lineSpacingMultiplier="@fraction/detail_body_line_spacing_multiplier" />
    </android.support.v4.widget.NestedScrollView>

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/share_fab"
        android:stateListAnimator="@anim/fab_state_list_anim"
        android:background="@drawable/add_fab_background"
        android:layout_marginRight="@dimen/fab_margin"
        android:layout_width="56dp"
        android:layout_height="56dp"
        android:src="@drawable/ic_share"
        android:elevation="@dimen/fab_elevation"
        android:contentDescription="@string/action_share"
        app:layout_anchor="@id/main.appbar"
        app:layout_anchorGravity="bottom|right|end"/>

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

Answer 1

try this make small change in your FloatingActionButton

<android.support.design.widget.FloatingActionButton
        android:id="@+id/share_fab"
        android:stateListAnimator="@anim/fab_state_list_anim"
        android:background="@drawable/add_fab_background"
        android:layout_marginRight="@dimen/fab_margin"
        android:layout_width="56dp"
        android:layout_height="56dp"
        android:src="@drawable/ic_share"
        android:elevation="@dimen/fab_elevation"
        android:contentDescription="@string/action_share"
        app:layout_anchor="@id/main_collapsing"
        app:layout_anchorGravity="bottom|right|end"/>