android - Fragment Layout not corresponding to preview -

so, first of i'm new android may dumb question, but..

i have in mainactivity layout viewpager calls fragments of different type (i have made 4-5 xml layout displaying different informations)

despite created layout basing on weighed linearlayout maximize compatibility, in preview visibility seems perfect in each device selected, once load application on phone, layout has bizarre behavior.

here example (preview vs. screenshot device)

i'm not sure made mistake, know:

1) happened

2) cause behaviour

3) how fix (a link guide welcome)

thanks much!