How to make corner radius in android

I am trying to make a gridview which will have an image and text beneath it with corner radius effect. So far it seems not possible. Here is my Activity xml which is holding the gridview:

<ScrollView
    android:layout_width="match_parent"
    android:fillViewport="true"
    android:layout_height="match_parent">
    <GridView
        android:id="@+id/gridview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:columnWidth="140dp"
        android:padding="5dp"
        android:layout_marginTop="10dp"
        android:numColumns="auto_fit"
        android:verticalSpacing="5dp"
        android:horizontalSpacing="5dp"
        android:stretchMode="columnWidth"
        android:gravity="center"/>
</ScrollView>

Here is the adapter xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              xmlns:app="http://schemas.android.com/apk/res-auto"
              android:orientation="vertical"
              android:layout_height="wrap_content"
              android:padding="2dp"
              android:layout_margin="20dp"
              android:background="@drawable/grid_corner_radius"
              android:layout_width="wrap_content">
    <ImageView
        android:layout_width="200dp"
        android:background="@drawable/cat_life"
        android:layout_height="160dp"/>

    <TextView
        android:layout_width="200dp"
        android:layout_height="40dp"
        android:id="@+id/credit_textView"
        android:gravity="center"
        android:text="Life"
        android:textColor="#FFFFFF"
        android:background="@color/colorPrimary"
        android:textSize="15dp"/>
</LinearLayout>    

And finally here is the corner radius magic code:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape xmlns:android="http://schemas.android.com/apk/res/android" >
            <solid android:color="#C0C0C0"></solid>
            <corners android:radius="15dp"></corners>
        </shape>
    </item>
</selector>

And the output is as under:

See the image's sharp rectangle edge is visible. What could be the possible solution?