Textview value reset when fragment changes

Question

I have 3 fragments: [A], [B] and [C].
Fragment [A] has a text view and a button that can change the value of the text view.

Stutation 1: textview with attribute: android:textIsSelectable="true" .
Stand on [A], change the value of the text field from "Hello World" to "1", go to [C] and go back to [A], the value of the text view is "1".
Image: Stutation 1

Plasterer 2: text image with attribute: android:textIsSelectable="false" .
Stand on [A], change the value of the text field from "Hello World" to "1", goto [C] and go back to [A], the value of textview has changed to the default value "Hello World".
Image: Stutation 2

Can you tell me why?
Is this a structure error?
Thank you very much!