折叠工具栏布局不工作

我的目标是滚动viewpager时 ConstraintLayout 必须关闭并将标签粘在下面吗 app_barTop

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 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:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/white">

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

    </android.support.v4.view.ViewPager>

    <android.support.design.widget.AppBarLayout
        android:id="@+id/app_barTop"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@android:color/white">

        <android.support.design.widget.AppBarLayout
            android:id="@+id/app_bar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@android:color/white">

            <include layout="@layout/status_bar" />

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                android:elevation="@dimen/toolbarElevation"
                app:contentInsetStart="0dp"
                tools:ignore="UnusedAttribute">

                <RelativeLayout
                    android:layout_width="match_parent"
                    android:layout_height="match_parent">

                    <ImageView
                        android:id="@+id/img_plus"
                        android:layout_width="?attr/actionBarSize"
                        android:layout_height="?attr/actionBarSize"
                        android:layout_alignParentEnd="true"
                        android:scaleType="center"
                        android:src="@drawable/fab_plus"
                        android:tint="@color/app_color"
                        tools:ignore="ContentDescription" />

                    <ImageView
                        android:id="@+id/img_message"
                        android:layout_width="?attr/actionBarSize"
                        android:layout_height="?attr/actionBarSize"
                        android:scaleType="center"
                        android:src="@drawable/icon_message"
                        tools:ignore="ContentDescription" />

                    <ImageView
                        android:id="@+id/img_search"
                        android:layout_width="?attr/actionBarSize"
                        android:layout_height="?attr/actionBarSize"
                        android:layout_toStartOf="@id/img_plus"
                        android:scaleType="center"
                        android:src="@drawable/icon_search"
                        tools:ignore="ContentDescription" />

                    <TextView
                        android:id="@+id/toolbar_title"
                        android:layout_width="wrap_content"
                        android:layout_height="match_parent"
                        android:layout_toEndOf="@id/img_message"
                        android:layout_toStartOf="@id/img_search"
                        android:fontFamily="sans-serif-medium"
                        android:gravity="center_vertical"
                        android:text="@string/vouch"
                        android:textColor="@color/action_bar_color"
                        android:textSize="18sp" />

                </RelativeLayout>

            </android.support.v7.widget.Toolbar>

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

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/collapsing_toolbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:layout_scrollFlags="scroll|exitUntilCollapsed">

            <android.support.constraint.ConstraintLayout 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:layout_width="match_parent"
                android:layout_height="wrap_content">

                <Button
                    android:id="@+id/btn_view_contacts"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_marginBottom="8dp"
                    android:layout_marginEnd="8dp"
                    android:layout_marginStart="8dp"
                    android:layout_marginTop="8dp"
                    android:text="View Contacts"
                    android:textAllCaps="false"
                    app:layout_constraintBottom_toBottomOf="parent"
                    app:layout_constraintEnd_toEndOf="parent"
                    app:layout_constraintHorizontal_bias="0.1"
                    app:layout_constraintStart_toStartOf="parent"
                    app:layout_constraintTop_toTopOf="parent" />

                <Button
                    android:id="@+id/btn_edit_profile"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_marginBottom="8dp"
                    android:layout_marginEnd="8dp"
                    android:layout_marginStart="8dp"
                    android:layout_marginTop="8dp"
                    android:text="Edit Profile"
                    android:textAllCaps="false"
                    app:layout_constraintBottom_toBottomOf="parent"
                    app:layout_constraintEnd_toEndOf="parent"
                    app:layout_constraintHorizontal_bias="0.9"
                    app:layout_constraintStart_toStartOf="parent"
                    app:layout_constraintTop_toTopOf="parent" />

            </android.support.constraint.ConstraintLayout>

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

        <android.support.design.widget.TabLayout
            android:id="@+id/tabLayout"
            android:layout_width="match_parent"
            android:layout_height="?android:attr/actionBarSize"
            android:layout_gravity="bottom"
            android:background="@android:color/transparent"
            app:layout_scrollFlags="scroll|enterAlways"
            app:tabGravity="fill"
            app:tabIndicatorColor="@android:color/holo_orange_dark"
            app:tabMaxWidth="0dp"
            app:tabMode="fixed"
            app:tabSelectedTextColor="@android:color/black"
            app:tabTextAppearance="@android:style/TextAppearance.Widget.TabWidget"
            app:tabTextColor="@android:color/black" />

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


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