Android中Context到底是什么以及用法

　　这是Stackoverflow上一位网友的回答：

　　原地址：http://stackoverflow.com/questions/3572463/what-is-context-in-android

As the name suggests, its the context of current state of the application/object. It lets newly created objects understand what has been going on. Typically you call it to get information regarding another part of your program (activity, package/application)

You can get the context by invoking getApplicationContext(), getContext(), getBaseContext() or this (when in the activity class).

Typical uses of context:

• Creating New objects: Creating new views, adapters, listeners:

  1 TextView tv = new TextView(getContext());
  2 ListAdapter adapter = new SimpleCursorAdapter(getApplicationContext(), ...);

• Accessing Standard Common Resources: Services like LAYOUT_INFLATER_SERVICE, SharedPreferences:

  1 context.getSystemService(LAYOUT_INFLATER_SERVICE)
  2 getApplicationContext().getSharedPreferences(*name*, *mode*);

• Accessing Components Implicitly: Regarding content providers, broadcasts, intent

　　　　getApplicationContext().getContentResolver().query(uri, ...);