找不到coordinatorlayout

Question

的錨這是我的佈局：

<?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: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="mybitchinapp.cortana.com.musica.MainActivity" 
    tools:showIn="@layout/app_bar_main" 
    android:weightSum="7" 
    android:orientation="vertical"> 


    <LinearLayout 
     android:layout_height="match_parent" 
     android:layout_width="match_parent" 
     android:layout_below="@+id/layout_upper" 
     android:layout_weight="3"> 
     <android.support.v7.widget.CardView 

      android:layout_width="match_parent" 
      android:layout_height="wrap_content" 
      android:id="@+id/cardview" 
      android:layout_marginRight="16dp" 
      android:layout_marginLeft="16dp" 
      android:layout_marginTop="16dp" 
      android:layout_marginBottom="16dp"> 

      <ImageView 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:id="@+id/song_imgview"/> 

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

    </LinearLayout> 

    <LinearLayout 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:layout_weight="4" 
     android:id="@+id/layout_lower" 
     android:orientation="vertical"> 

    </LinearLayout> 
    <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" 
     app:layout_anchor="@id/layout_upper" 
     app:layout_anchorGravity="bottom|right|end" 
     /> 
</android.support.design.widget.CoordinatorLayout> 

我需要我FloatingActionButton是在兩個佈局的中心。但在運行這個佈局的應用程序，堆棧跟蹤是：

 java.lang.IllegalStateException: Could not find CoordinatorLayout descendant view with id mybitchinapp.cortana.com.musica:id/layout_upper to anchor view android.support.design.widget.FloatingActionButton{b0a6a5b VFED..C.. ......I. 0,0-0,0 #7f0c0070 app:id/fab} 
                       at android.support.design.widget.CoordinatorLayout$LayoutParams.resolveAnchorView(CoordinatorLayout.java:2489) 

爲什麼不能找到錨佈局？它已在此佈局文件中定義。請幫助

Answer 1

<LinearLayout 
     android:layout_height="match_parent" 
     android:layout_width="match_parent" 
     android:layout_below="@+id/layout_upper" 
     android:layout_weight="3"> 

到

<LinearLayout 
     android:id="@+id/layout_upper" 
     android:layout_height="match_parent" 
     android:layout_width="match_parent" 
     android:layout_weight="3">