android - What's happening to my Fragments? -

i know there tons of questions fragments , read many, seems haven't grasped yet.

my app has 9 fragments. on 1 of them, fragment x, playing media , there shows fragment on screen, y. perform that, thought best using replace().

my relevant code:

// button clicked, goes x y getfragmentmanager().begintransaction()                 .replace(r.id.container, fragmenty)                 .commit(); 

when onbackpressed() called , fragmenty 1 returned fragmentmanager.findfragmentbyid(r.id.container):

fragmentmanager.begintransaction()                     .replace(r.id.container, fragmentx)                     .commit(); 

expected behavior: it'd remove x , add y. when going back, it'd remove y , add x.

what happened: first time go y, y shown expected, x still running hear audio playing. when go back, y disappears , seems fine. however, next time click go y, x destroyed (audio stops playing) , app gets weird, since actionbar shows , shouldn't. moreover, keep hidden fragment map gets blank after executing that.

i imagine replace() not removes current fragment, of visible fragments. doing .remove(x).add(y, "y") not show fragment.

any help?

edit: asked, fragment x can added activity different points on app, hence on different ways. they're two:

// if backpressed , current fragment fragmenttransaction.remove(fragmenta).add(r.id.container, objectfragment).commit(); 

or

// if backpressed , current fragment b (map) fragmenttransaction.hide(fragmentb).add(r.id.container, objectfragment).commit(); 

most of times must know coming , i'm going, that's why did not use addtobackstack().

i try manage adding fragment stack, using

addtobackstack(string name) method.

there helpful answer on subject here: difference between add(), replace(), , addtobackstack()