Using below Layout code you can create a Radial Gradient, Here I have created a Gradient.xml layout by using shape and gradient property. By using GradientDrawer we can make smooth transition between two or three colors in liner, radial or sweep pattern. The below exampel layout will clearly describe you to make Radial Gradient.

Step(1)-MainActivity-

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

Step(2)-Actvity_Main layout-

<RelativeLayout 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: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=".MainActivity" >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:text="@string/hello_world"
        android:background="@drawable/gradient"
         />

</RelativeLayout>

Step(3)- Create Gradient.xml layout

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="oval"
    android:useLevel="false" >

    <gradient
        android:centerColor="#000000"
        android:endColor="#ffffff"
        android:gradientRadius="300"
        android:startColor="#ffffff"
        android:type="radial"
        android:useLevel="false" />

</shape>