Make Android Edit text field allows only for selected characters

There is a simple method to make a restrict or a limit on allowed characters in Android edit text field.
Eg: Suppose that you want to make a restrict where user only allows to type  a,e,i,o,u. You can easily do this by using following line in your layout.xml file

android:digits="aeiou"

Eg: (I used edit text in relative layout)

     <EditText
         android:id="@+id/editText1"
         android:digits="aeiou"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentLeft="true"
         android:layout_alignParentTop="true"
         android:layout_marginLeft="54dp"
         android:layout_marginTop="123dp" >
         <requestFocus />
     </EditText>