swift app切换至后台的检测

@objc func applicationWillResignActive() {

        if(self.isViewLoaded && (self.view.window != nil)){

            print("进入后台")

        }

    }

    @objc func applicationDidBecomeActive() {

        if(self.isViewLoaded && (self.view.window != nil)){

            print("进入前台")

        }

    }