My android app killed when the back is press

i would like to know why my app is killed when i press the back button on my android phone

it is because the pages are loaded via ajax and the main app does not change. if you hit the button your phone will jump to the previous page … i put this little code in my js code. that kills the history and so yout button has no page to jump to…

// History killer
history.pushState(null, null, location.href);
    window.onpopstate = function () {

it was google map plugin which was causing that