Hi Praveen,
The issue with your implementation is that you do not need the XML if you are programmatically adding the NativeExpressAdView to your layout. So you can clean up the redundant XML's AdView code.
The other issue is that you are adding a NativeExpressAdView (mAdView) into another NativeExpressAdView (adViewContainer). The parent of your NativeExpressAdView has to be a layout (RelativeLayout, et al.). So change that and you should be able to see your ad rendered, at full-width.
P.S: The default RelativeLayout from Android has all-around paddings (16dp) so you might need to remove the paddings (I did) to get the ad to show.
Vu Chau
Mobile Ads SDK Team