Align view on top of a LinearLayout

How to align a view over a linear layout? (In the bottom left).

I want the blue ball to look like this:

However,thewayI'mtryingtodoitlookslikethis:

Layoutxml:

<?xmlversion="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:Font="http://schemas.android.com/apk/res-auto"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:id="@+id/notificationItemLayout"
        android:background="@drawable/layout_border"
        android:layout_marginLeft="20dp">

    <com.mmp.customview.DefaultTextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        Font:isLight="true"
        android:id="@+id/notificationDataTextView"
        tools:text="Message log 1/7/2017"
        android:layout_marginTop="8dp" />

        <com.mmp.customview.DefaultTextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            Font:isLight="true"
            android:textSize="17sp"
            android:textColor="#A9D3E7"
            android:id="@+id/notificationTextView"
            tools:text="Message log 1/7/2017"
            android:paddingTop="15dp"
            android:paddingLeft="15dp"
            android:paddingRight="15dp"
            android:paddingBottom="10dp"
            android:layout_marginTop="8dp" />

    </LinearLayout>

    <com.mmp.customview.NotificationIconView
        android:layout_width="50dp"
        android:layout_height="50dp"
        android:layout_alignBottom="@+id/notificationItemLayout"
        android:layout_alignLeft="@+id/notificationItemLayout"
        android:layout_centerHorizontal="true"
        android:id="@+id/notificationIcon" />

</RelativeLayout>