Does FragmentTabHost need TabWidget to be defined explicitly

Question

I'm trying to implement an Activity with 3 tabs on it. I decided to use FragmentTabHost for this purpose. I've found some code examples with following layout file:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <android.support.v4.app.FragmentTabHost
        android:id="@android:id/tabhost"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <TabWidget 
            android:id="@android:id/tabs"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal"/>
    </android.support.v4.app.FragmentTabHost>

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

But I was surprised when understood that previous code sample works the same way without TabWidget:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <android.support.v4.app.FragmentTabHost
        android:id="@android:id/tabhost"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
    </android.support.v4.app.FragmentTabHost>

    <FrameLayout 
        android:id="@+id/realtabcontent"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        />

</LinearLayout>

I just see my tabs as intended. According to the source code for FragmentTabHost, it creates TabWidget by itself if could not find it in the hierarchy of views. So I wonder if I should declare TabWidget explicitly in my layout file or not.

Answer 1

Well, the behavior that you describe is not documented, so there's a slight risk of regression if they drop this feature someday. Of course, having the TabWidget child is also undocumented, since the documentation for FragmentTabHost sucks.

You might also put the TabWidget in your layout if you want declarative control, via XML attributes, of some aspects of the TabWidget rendering.

Otherwise, though, if the default generated TabWidget works for you, you are welcome to use it.