Where is scrollbar in listView?

问题

In the .xml file, a layout written shows as follow, pls check up,

<RelativeLayout xmlns:tools="http://schemas.android.com/tools"
 xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="wrap_content"
 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"
 tools:context=".SecondActivity" >

<ListView
    android:id="@+id/listView1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginLeft="15dp"
    android:layout_toRightOf="@+id/button1a"
    android:background="@color/dodgerblue"
    android:entries="@array/Planets"
    android:paddingRight="@dimen/activity_vertical_margin"
    android:scrollbarStyle="insideInset"
    android:scrollbars="vertical" >

</ListView>

<TextView
    android:id="@+id/textView2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/textView1"
    android:layout_below="@+id/textView1"
    android:layout_marginTop="16dp"
    android:text="@string/Medium_Text"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:textColor="@color/green" />
</RelativeLayout>

Build gets through, But when run in emulator, there is no scrollbar in the listview, what's matter?

<string-array name="Planets">  
    <item>Mercury</item>  
    <item>Venus</item>  
    <item>Earth</item>  
    <item>Mars</item>  
    <item>Jupiter</item>  
    <item>Saturn</item>  
    <item>Uranus</item>  
    <item>Neptune</item>  
    <item>Pluto</item>                 
    <item>Moon</item>
    <item>Satellite</item>

</string-array>

this is array data. and can add more data bellow.

来源：https://stackoverflow.com/questions/20471731/where-is-scrollbar-in-listview