Android支持FragmentTabs示例中的两个框架布局支持4Demos

Question

我是Android中的新片段，我指的是片段演示示例为supprotv4兼容性库提供的。

任何人都可以解释为什么Android Support4Demos的FragmentTabs.java示例中有两个框架布局(@+android:id/realtabcontent , @android:id/tabcontent)。

FragmentTabs.java调用setContentView(R.layout.fragment_tabs);方法和以下是相同的布局文件。

fragment_tabs.xml

<TabHost xmlns:android="http://schemas.android.com/apk/res/android" 
     android:id="@android:id/tabhost" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" > 

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

      <TabWidget 
       android:id="@android:id/tabs" 
       android:layout_width="match_parent" 
       android:layout_height="wrap_content" 
       android:layout_weight="0" 
       android:orientation="horizontal" /> 

      <FrameLayout 
       android:id="@android:id/tabcontent" 
       android:layout_width="0dp" 
       android:layout_height="0dp" 
       android:layout_weight="0" /> 

      <FrameLayout 
       android:id="@+android:id/realtabcontent" 
       android:layout_width="match_parent" 
       android:layout_height="0dp" 
       android:layout_weight="1" /> 
     </LinearLayout> 

    </TabHost> 

在此先感谢

Answer 1

通过例子去后，我发现下面的评论中FragmentsTabs.java

/** 
* This is a helper class that implements a generic mechanism for 
* associating fragments with the tabs in a tab host. It relies on a trick. 
* Normally a tab host has a simple API for supplying a View or Intent that 
* each tab will show. This is not sufficient for switching between 
* fragments. So instead we make the content part of the tab host 0dp high 
* (it is not shown) and the TabManager supplies its own dummy view to show 
* as the tab content. It listens to changes in tabs, and takes care of 
* switch to the correct fragment shown in a separate content area whenever 
* the selected tab changes. 
*/