Android viewpager自动轮播和小圆点联动效果

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  xmlns:tools="http://schemas.android.com/tools"  android:layout_width="match_parent"  android:layout_height="match_parent"  android:orientation="vertical" >  <RelativeLayout    android:layout_width="match_parent"    android:layout_height="200dp" >    <android.support.v4.view.ViewPager      android:id="@+id/main_vp"      android:layout_width="match_parent"      android:layout_height="200dp" >    </android.support.v4.view.ViewPager>    <LinearLayout      android:id="@+id/ll_doc"      android:layout_width="match_parent"      android:layout_height="40dp"      android:layout_alignParentBottom="true"      android:gravity="center"      android:orientation="horizontal" >    </LinearLayout>  </RelativeLayout>  <LinearLayout    android:layout_width="match_parent"    android:layout_height="100dp" >  </LinearLayout>  <LinearLayout    android:layout_width="match_parent"    android:layout_height="80dp" >  </LinearLayout>  <GridView    android:id="@+id/main_gv"    android:layout_width="match_parent"    android:layout_height="match_parent"     android:numColumns="2"    >  </GridView></LinearLayout>