Settext issue in ViewPager particular version - 5.1.1 android?

I am building android application where I am using Custom ViewPager. The Problem is explain below in the following steps:

1. When I open new activity of ViewPager and click on any button and setText any particular value to it. It's working fine.
2. Problem occurs when I swipe left-right and then click on button to setText on particular TextView; the value gets set as I can toast the value of TextView using getText. But the value does not change in the UI. For exmaple - I swipe any page and now the TextView contains my current position as 2. If I click button and try to do setText(position++) and toast the value, the incremented value is shown in the toast
3. But still TextView showing 2.

This issue is coming particular in 5.1.1.