Why does current activity apply setting of previous activity?

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http://stackoverflow.com – My app has 2 activities: - Activity (1) has a button to start Activity (2), this button isn't set transparent - Activity (2) has a button that is transparent by setAlpha() My problem is sometimes, when I back to Activity (1) from Activity (2) by pressing back button, a button of Activity (1) becomes transparent same as button of Activity (2). I don't know why this problem can occur, please help me ... Thanks!!! :( (HowTos)