Float Action Button does not get fixed at the footer with Collapsing Actionbar/Toolbar

Question

I have a Fragment with Coordinator layout, recyclerview and a Float Action Button, and in the view that calls this Fragment has a tablayout that hides and appears as you go up or down the Recycler view, I have tried several ways to leave Fab fixed in the footer, but anyway it always rises when slips the view Recycler

follows below the code of Fragment:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/frmLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context="br.com.julioantonini.meuchat.ContatosFragment">


<android.support.v7.widget.RecyclerView
    android:id="@+id/recyclerContatos"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"/>

<android.support.design.widget.FloatingActionButton
    android:id="@+id/fab"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="bottom|end"
    android:layout_marginBottom="70dp"
    android:layout_marginRight="10dp"
    android:layout_marginEnd="10dp"
    app:elevation="1dp"
    app:srcCompat="@drawable/ic_action_add"
    app:layout_anchor="@id/recyclerContatos"
    app:layout_anchorGravity="bottom|right|end"/>

and below the code of Activity:

<?xml version="1.0" encoding="utf-8"?>

<android.support.design.widget.AppBarLayout
    android:id="@+id/appbar"
    android:layout_height="wrap_content"
    android:layout_width="match_parent">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        app:layout_scrollFlags="scroll|enterAlways"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary" />


    <android.support.design.widget.TabLayout
        android:id="@+id/tab_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        app:tabIndicatorColor="@color/colorTab"/>

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


<android.support.v4.view.ViewPager
    android:id="@+id/viewPager"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_below="@id/appbar"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"/>

Answer 1

If you have no problem putting your FAB in activity, you can do it this way:

...
<android.support.v4.view.ViewPager
    android:id="@+id/viewPager"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_below="@id/appbar"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"/>
<android.support.design.widget.FloatingActionButton
    android:id="@+id/fab"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="bottom|end"
    android:layout_marginBottom="70dp"
    android:layout_marginRight="10dp"
    android:layout_marginEnd="10dp"
    app:elevation="1dp"
    app:srcCompat="@drawable/ic_action_add"
    app:layout_anchor="@id/viewPager"
    app:layout_anchorGravity="bottom|right|end"/>

What changes here is that the layout_anchor of your FAB is no longer the RecyclerView and becomes the ViewPager. In addition to, of course, removing the FAB of the layout of your fragment and move on to the activity.