滑动栏效果

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

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="200dp">

        <android.support.design.widget.CollapsingToolbarLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:theme="@style/Theme.AppCompat.DayNight.DarkActionBar"
            app:layout_scrollFlags="scroll|exitUntilCollapsed"
            android:background="@android:color/white">
            <!-- 。。。顶部布局。。。-->

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

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

    <!--
         android:fillViewport="true"
         在ScrollView中嵌套 viewpager
        必须设置android:fillViewport="true"
    -->

    <android.support.v4.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:fillViewport="true"
        app:layout_behavior="@string/appbar_scrolling_view_behavior">
        <!--  。。。底部布局。。。-->
        <!--只能有一个直接子布局-->
        
    </android.support.v4.widget.NestedScrollView>
</android.support.design.widget.CoordinatorLayout>