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androidandroid-context

What is 'Context' on Android?

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.

Solution

  • 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, ...);