主要是用到了Accessibility,它是Android从API 4开始提供的一个功能，主要目的是帮助一些因为有视觉，听觉，身体障碍而无法完全使用触摸屏或铃声等的用户来使用Android的,但现在很多开发者都用它来实现一些其他功能，比如说微信抢红包，自动安装APK，强制停止应用等.实际上就是通过监视一个应用的界面元素状态的变化,来自动响应执行一些操作.(The main use of Accessibility, which is a function that Android provides from API 4, is designed to help users with visual, auditory, physical barriers that can't use Android with a touch screen or ringtone, but now many developers use it to implement some other functions, such as WeChat. Robbing red packets, installing APK automatically, forcing the application to stop, and so on. In fact, it automatically responds to some operations by monitoring the changes in the state of an applied interface element.)