What is different between getContext and getActivity from Fragment in support library?
AndroidAndroid Problem Overview
What is different between getContext()
and getActivity()
from Fragment
in support library?
Do they always return the same object? (activity associated with current fragment)
Android Solutions
Solution 1 - Android
In most cases there is no difference but ...
So originally Fragments
were hosted in FragmentsActivity
and back then to get Context
one called getActivity()
.
Just checked the sources and Fragments
now can be hosted by anyone implementing FragmentHostCallback interface. And this changed in Support Library version 23, I think.
When using newer version of Support Library, when Fragment
is not hosted by an Activity
you can get different objects when calling getActivity()
and getContext()
.
When you call getActivity()
you get an Activity
which is a Context
as well.
But when you call getContext
you will get a Context
which might not be an Activity
.
Solution 2 - Android
So far, the only provided implementation of FragmentHostCallback
(in the OS and the support library) always returns the same value for both getContext()
and getActivity()
.
However, the other constructors of FragmentHostCallback
suggest that in future implementations, we may get:
- A null
Activity
and a non-nullContext
which is not anActivity
. This looks improbable but we can imagine that fragments could be used outside Activities in the future, or be fully sandboxed. - A non-null
Activity
and a non-nullContext
which is not the same instance as theActivity
. For example,Context
could be aContextThemeWrapper
.
Conclusion: when you can, use getContext()
. When you need Activity-specific calls, use getActivity()
.
Solution 3 - Android
Activity is a subclass of Context. Activity has also Window elements and access to UI methods, Context doesn't. However, in the majority of the cases, it's the same if you need only the Context.
Solution 4 - Android
getContext():- Returns the context the view is currently running in. Usually the currently active Activity. getContext()
is not defined in an Activity. It's used in a View (or View subclass) to get a reference to the enclosing context (an Activity).
getActivity():- This method gives the context of the Activity. You can use it is like the yourActivity.this
. getActivity() is normally used in fragments to get the context of the activity in which they are inserted or inflated.
Solution 5 - Android
getContext() - Returns the context view only current running activity.
getActivity()- Return the Activity this fragment is currently associated with.
getActivity()
can be used in a Fragment for getting the parent Activity of the Fragment .
Solution 6 - Android
You can use getActivity()
, which returns the activity associated with a fragment. The activity is a context (since Activity extends Context).
getActivity()
can return null if it is called before onAttach of the respective fragment. Context provides information about the Actvity or Application to newly created components. Relevant Context should be provided to newly created components (whether application context or activity context). Since Activity is a subclass of Context, one can use this to get that activity's context.
getContext()
Returns the context view only current running activity.
Solution 7 - Android
> Returns the context view only current running activity.
> Return the Activity this fragment is currently associated with.
Solution 8 - Android
/**
* Return the {@link Context} this fragment is currently associated with.
*/
public Context getContext() {
return mHost == null ? null : mHost.getContext();
}
/**
* Return the {@link FragmentActivity} this fragment is currently associated with.
* May return {@code null} if the fragment is associated with a {@link Context}
* instead.
*/
final public FragmentActivity getActivity() {
return mHost == null ? null : (FragmentActivity) mHost.getActivity();
}
from source code, we can find that when a fragment is attached to an Activity, getContext returns null. While getActivity returns null when a fragment is attached to context instead