active application suddenly come in foreground after undefined time

I have created an android application (let us call it cecile),

when i launch this application (when cecile become active), i switch to any other application (may be web browser, google...) and work within this apps, suddenly the application that i have created (cecile) suddenly move from background to foreground. I don't know what i did (may be the pushNotification )that cause this unexpected behaviour in my own application (the behaviour of moving my active application suddenly from background to foreground without i am clicking on).

Someone has any idea about this bug?