问题描述
In Android programming, what exactly is a Context class and what is it used for?
I read about it on the developer site, but I am unable to understand it clearly.
Putting it simply:
As the name suggests, it's the context of the 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 and package/application).
You can get the context by invoking getApplicationContext(), getContext(), getBaseContext() or this (when in a class that extends from Context, such as the Application, Activity, Service and IntentService classes).
Typical uses of context:
Creating new objects: Creating new views, adapters, listeners:
TextView tv = new TextView(getContext()); ListAdapter adapter = new SimpleCursorAdapter(getApplicationContext(), ...);Accessing standard common resources: Services like LAYOUT_INFLATER_SERVICE, SharedPreferences:
context.getSystemService(LAYOUT_INFLATER_SERVICE) getApplicationContext().getSharedPreferences(*name*, *mode*);Accessing components implicitly: Regarding content providers, broadcasts, intent
getApplicationContext().getContentResolver().query(uri, ...);
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