Resume don't clear field data

Hi All
I had a Ionic + AngularJS Android app

Inside include
page1 = page1.html (include some textbox)
page2 = page2.html (include some textbox)
index.html is $state.go(page1)

When I input text “Test” in textbox of page1.html

Then click Android hardware backbutton
My app down to background
Then I let the app go to top

But textbox of page1.html is empty

How can don’t refresh app

Thank you