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In Android programming, what exactly
is a Context
class and what is it used
for?
I read about it on the href="https://d.android.com/reference/android/content/Context"
rel="noreferrer">developer site, but I am unable to understand it
clearly.
Putting it
simply:
As the name suggests, it's
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 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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