Question

Android下Context，Activity，Application之间有什么区别

Answer 1

Context，中文直译为“上下文”，SDK中对其说明如下：
Interface to global information about an application environment. This is an abstract class whose implementation
is provided by the Android system. It allows access to application-specific resources and classes, as well as up-calls
for application-level operations such as launching activities, broadcasting and receiving intents, etc。
从上可知一下三点即：

1、它描述的是一个应用程序环境的信息，即上下文。
2、该类是一个抽象(abstract class)类，Android提供了该抽象类的具体实现类(后面咱们会讲到是ContextIml类)。
3、通过它咱们可以获取应用程序的资源和类，也包括一些应用级别操作，例如：启动一个Activity，发送广播，接受Intent信息等。