firebase - Android navigation blank view on navigate between fragment

Question

I create 2 fragment with drawer navigation

1. add travel
2. view travels

My Problem is when I open the "view travels" screen its seems ok, and I see the list of travels. but when I open the "add travel fragment" I see the page but the navigation bar does not shown. and after click on "Back" I show the navigation but while clicking the "view travels" I get a blank view without the list of data.

My 2 questions is: 1- what the reason that the navigation does not shown on the "add travel" page 2- What can be the reason that after show single fragment the other is blank. (maybe its because those 2 fragment share same modelview)

Thanks Here is some screenshots:

Answer 1

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