Android back button

-- this goes to your main.lua
local _IS_ANDROID, _IS_IOS
if platform == 'Android' then
    _IS_ANDROID = true
elseif platform == 'iPhone OS' then
    _IS_IOS = true
end

if _IS_ANDROID then
    Runtime:addEventListener('key', function (event)
            if event.keyName == 'back' and event.phase == 'down' then
                local scene = storyboard.getScene(storyboard.getCurrentSceneName())
                if scene and type(scene.backPressed) == 'function' then
                    return scene:backPressed()
                end
            end
        end);
end



-- and this goes to your storyboard scenes
function scene:backPressed()
    storyboard.gotoScene('scenes.menu', 'slideRight', 500) -- go to previous screen
    return true
end


-- But in your main menu scene you should ask the user if he wants to exit on back button press
-- I have this code:
function scene:backPressed()
    if not self.closeDialogShown then
        self.closeButton._view._onRelease()
    end
    return true
end

-- and close button in create scene:
    self.closeButton = widget.newButton{
        label = 'Exit',
        onRelease = function ()
                self.closeDialogShown = true
                native.showAlert('Exit?', 'ARE YOU SURE YOU WANT TO EXIT?', {'NO', 'YES'}, function (event)
                        self.closeDialogShown = false
                        if event.index == 2 then
                            if _IS_ANDROID then
                                native.requestExit()
                            else
                                os.exit()
                            end
                        end
                    end}
            end}