即使使用了NestedScrollView，ToolBar也無法徹底滾動屏幕

我希望TabLayout保持在屏幕中，滾動時ToolBar不在屏幕上，但ToolBar始終有一部分保留在屏幕中。我在互聯網上搜索了一些代碼並運行它們，但它們具有相同的結果。即使使用了NestedScrollView，ToolBar也無法徹底滾動屏幕

<?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:fitsSystemWindows="true" 
tools:context="com.ihandy.a2014011385.MainActivity"> 

<android.support.design.widget.AppBarLayout 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:theme="@style/AppTheme.AppBarOverlay"> 

    <android.support.v7.widget.Toolbar 
     android:id="@+id/toolbar" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:background="?attr/colorPrimary" 
     app:popupTheme="@style/AppTheme.PopupOverlay" 
     app:layout_scrollFlags="scroll|enterAlwaysCollapsed"/> 

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

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

<android.support.v4.widget.NestedScrollView 
    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:paddingBottom="@dimen/activity_vertical_margin" 
    android:paddingLeft="@dimen/activity_horizontal_margin" 
    android:paddingRight="@dimen/activity_horizontal_margin" 
    android:paddingTop="@dimen/activity_vertical_margin" 
    app:layout_behavior="@string/appbar_scrolling_view_behavior" 
    tools:context="com.ihandy.a2014011385.MainActivity" 
    tools:showIn="@layout/app_bar_main"> 

    <LinearLayout 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:orientation="vertical"> 

     <TextView 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content" 
      android:text="@string/large_text"/> 
    </LinearLayout> 

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

<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_margin="@dimen/fab_margin" 
    android:src="@android:drawable/ic_dialog_email" /> 

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

和Java代碼

TabLayout channels = (TabLayout)findViewById(R.id.channels_tabs); 
channels.setTabMode(TabLayout.MODE_SCROLLABLE); 
channels.addTab(channels.newTab().setText("123")); 
channels.addTab(channels.newTab().setText("123")); 
channels.addTab(channels.newTab().setText("123"));

這是效果現在