如何解決ClassCastException異常的LinearLayout.LayoutParams VS CoordinatorLayout.LayoutParams

Question

我試圖創建一個FloatingActionButton像this，但是當我運行應用程序有以下錯誤

java.lang.ClassCastException: android.widget.LinearLayout$LayoutParams cannot be cast to android.support.design.widget.CoordinatorLayout$LayoutParams 
                   at android.support.design.widget.FloatingActionButton$Behavior.isBottomSheet(FloatingActionButton.java:597) 
                   at android.support.design.widget.FloatingActionButton$Behavior.onDependentViewChanged(FloatingActionButton.java:589) 
                   at android.support.design.widget.FloatingActionButton$Behavior.onDependentViewChanged(FloatingActionButton.java:528) 

這裏是我的layout.xml文件

<android.support.design.widget.CoordinatorLayout 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:app="http://schemas.android.com/apk/res-auto" 
    xmlns:fresco="http://schemas.android.com/apk/res-auto" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent"> 

    <android.support.v4.widget.NestedScrollView 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:id="@+id/discoverRView" 
     app:layout_behavior="@string/appbar_scrolling_view_behavior"> 

     <LinearLayout 
      android:layout_width="match_parent" 
      android:orientation="vertical" 
      android:layout_height="wrap_content"> 
      <LinearLayout 
       android:layout_width="match_parent" 
       android:layout_height="wrap_content" 
       android:id="@+id/description_layout" 
       android:padding="8dp" 
       android:background="@color/colorPrimaryDark" 
       android:orientation="vertical"> 

       <TextView 
        android:layout_width="match_parent" 
        android:layout_margin="5dp" 
        android:layout_height="wrap_content" 
        android:textStyle="bold" 
        android:textColor="@color/color_white_light" /> 
       <TextView 
        android:layout_width="match_parent" 
        android:layout_margin="4dp" 
        android:layout_height="match_parent" 
        android:lines="5" 
        android:scrollHorizontally="true" 
        android:ellipsize="end" 
        android:textColor="@color/color_event_text" 
        android:textAppearance="?android:attr/textAppearanceLarge" 
        android:textSize="15sp" 
        android:id="@+id/textView2" /> 
      </LinearLayout> 
      <LinearLayout 
       android:layout_width="match_parent" 
       android:layout_height="30dp" 
       android:background="@color/red_color" 
       android:id="@+id/fr_youare_at"> 

       <TextView 
        android:paddingLeft="12dp" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:id="@+id/you_are_at" 
        android:layout_gravity="center_vertical|left" 
        android:textColor="@android:color/white" 
        android:text="Interested" 
        android:textStyle="bold" /> 
      </LinearLayout> 
     </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_margin="16dp" 
     android:clickable="true" 
     android:src="@android:drawable/ic_menu_search" 
     app:layout_anchor="@id/description_layout" 
     app:layout_anchorGravity="bottom|right|end"/> 
</android.support.design.widget.CoordinatorLayout> 

我在做什麼錯？

Answer 1

我已經解決了它，佈局調用app:layout_anchor標籤必須是CoordinatorLayout