How to create transparent triangle with border on diagonal sides only?

Question

I need to draw below triangle with border on diagonal sides only.

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >
    <item>
        <vector
            android:width="400px"
            android:height="400px"
            android:viewportWidth="400.0"
            android:viewportHeight="400.0">

            <path
                android:fillColor="#0000FF"
                android:pathData="M0,0 L0,100 L50,50 z"/>

            <path
                android:pathData="M0,0 l50,0"
                android:strokeColor="@android:color/redColor"
                android:strokeWidth="1" />
        </vector>
    </item>
</layer-list>

Have been trying with that code but here what I get, the red line not even drawn!

Anyone can give me idea how to do it?