How can I get the context in a fragment?
I need to use my database whose constructor takes in the context, but getApplicationContext()
and FragmentClass.this
don't work so what can I do?
Database constructor
public Database(Context ctx)
{
this.context = ctx;
DBHelper = new DatabaseHelper(context);
}
You can use getActivity()
, which returns the activity associated with a fragment
.
The activity is a context
(since Activity
extends Context
).
To do as the answer above, you can override the onAttach
method of fragment:
public static class DummySectionFragment extends Fragment{
...
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
DBHelper = new DatabaseHelper(activity);
}
}
DatabaseHelper
needed a FragmentActivity
instead of an Activity
? For example, for an Adapter
...
onAttach(Activity activity)
then you should release it in onDetach()
onAttach
method has been deprecated, Overrides deprecated method in 'android.support.v4.app.Fragment'
The easiest and most precise way to get the context of the fragment that I found is to get it directly from the ViewGroup
when you call onCreateView
method at least here you are sure not to get null for getActivity()
:
public class Animal extends Fragment {
Context thiscontext;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
thiscontext = container.getContext();
Always use the getActivity() method to get the context of your attached activity, but always remember one thing: Fragments are slightly unstable and getActivity
returns null some times, so for that, always check the isAdded() method of fragment before getting context by getActivity()
.
Previously I'm using onAttach (Activity activity)
to get context
in Fragment
Problem
The onAttach (Activity activity)
method was deprecated in API level 23.
Solution
Now to get context in Fragment
we can use onAttach (Context context)
onAttach (Context context)
Called when a fragment is first attached to its context. onCreate(Bundle) will be called after this.
Documentation
/**
* Called when a fragment is first attached to its context.
* {@link #onCreate(Bundle)} will be called after this.
*/
@CallSuper
public void onAttach(Context context) {
mCalled = true;
final Activity hostActivity = mHost == null ? null : mHost.getActivity();
if (hostActivity != null) {
mCalled = false;
onAttach(hostActivity);
}
}
SAMPLE CODE
public class FirstFragment extends Fragment {
private Context mContext;
public FirstFragment() {
// Required empty public constructor
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
mContext=context;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rooView=inflater.inflate(R.layout.fragment_first, container, false);
Toast.makeText(mContext, "THIS IS SAMPLE TOAST", Toast.LENGTH_SHORT).show();
// Inflate the layout for this fragment
return rooView;
}
}
NOTE
We can also use getActivity()
to get context
in Fragments
but getActivity()
can return null
if the your fragment
is not currently attached to a parent activity
,
The correct way is to use
requireContext()
and the example
ContextCompat.getColor(requireContext(), R.color.colorAccent),
requireContext()
is considered correct when it may throw an exception? I believe it's a harmful way to use.
@Override
public void onAttach(Activity activity) {
// TODO Auto-generated method stub
super.onAttach(activity);
context=activity;
}
requireContext() method is the simplest option
requireContext()
Example
MyDatabase(requireContext())
You could also get the context from the inflater
parameter, when overriding onCreateView
.
public static class MyFragment extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
/* ... */
Context context = inflater.getContext();
/* ... */
}
}
Another alternative approach is:
You can get the context using:
getActivity().getApplicationContext();
to get the context inside the Fragment will be possible using getActivity()
:
public Database()
{
this.context = getActivity();
DBHelper = new DatabaseHelper(this.context);
}
Be careful, to get the Activity associated with the fragment using getActivity(), you can use it but is not recommended it will cause memory leaks.
I think a better aproach must be getting the Activity
from the onAttach()
method:
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
context = activity;
}
Activity.findViewById
is just a convenience method to search for a view in that activity's registered content view (set through setContentView
). In your correct example you are calling View.findViewById
, not Activity.findViewById
, and you are invoking the method on the correct root view. Totally different problem, and obviously you won't be able to find your view in a view hiearchy that doesn't hold that view.
getContext()
came in API 23. Replace it with getActivity() everywhere in the code.
See if it fixes the error. Try to use methods which are in between the target and minimun API level, else this error will come in place.
Since API level 23 there is getContext()
but if you want to support older versions you can use getActivity().getApplicationContext()
while I still recommend using the support version of Fragment
which is android.support.v4.app.Fragment
.
For Kotlin you can use context
directly in fragments. But in some cased you will find an error like
Type mismatch: inferred type is Context? but Context was expected
for that you can do this
val ctx = context ?: return
textViewABC.setTextColor(ContextCompat.getColor(ctx, android.R.color.black))
In kotlin just use activity
instead of getActivity()
getActivity()
is a child of Context so that should work for you
Use fragments from Support Library -
android.support.v4.app.Fragment
and then override
void onAttach (Context context) {
this.context = context;
}
This way you can be sure that context will always be a non-null value.
You have different options:
If your minSDK <= 21, then you can use getActivity(), since this is a Context.
If your minSDK is >=23, then you can use getContext().
If you don't need to support old versions then go with getContext()
.
safe way to get context in fragment
if(isAdded){
requireActivit();//this is your context
}
You can use the getActivity() method to get context or You can use getContext() method .
View root = inflater.inflate(R.layout.fragment_slideshow, container, false);
Context c = root.getContext();
I hope it helps!
Ideally, you should not need to use globals. The fragment has different notifications, one of them being onActivityCreated. You can get the instance of the activity in this lifecycle event of the fragment.
Then: you can dereference the fragment to get activity, context or applicationcontext as you desire:
this.getActivity()
will give you the handle to the activity this.getContext()
will give you a handle to the context this.getActivity().getApplicationContext()
will give you the handle to the application context. You should preferably use the application context when passing it on to the db.
The simple way is to use getActivity()
. But I think the major confusion of using the getActivity()
method to get the context here is a null pointer exception.
For this, first check with the isAdded()
method which will determine whether it's added or not, and then we can use the getActivity()
to get the context of Activity.
You can call getActivity()
or,
public void onAttach(Context context) {
super.onAttach(context);
this.activity = (CashActivity) context;
this.money = this.activity.money;
}
public class MenuFragment extends Fragment implements View.OnClickListener {
private Context mContext;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
FragmentMenuBinding binding=FragmentMenuBinding.inflate(inflater,container,false);
View view=binding.getRoot();
mContext=view.getContext();
return view;
}
}
I think you can use
public static class MyFragment extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Context context = getActivity.getContext();
}
}
I need context for using arrayAdapter IN fragment, when I was using getActivity error occurs but when i replace it with getContext it works for me
listView LV=getView().findViewById(R.id.listOFsensors);
LV.setAdapter(new ArrayAdapter<String>(getContext(),android.R.layout.simple_list_item_1 ,listSensorType));
On you fragment
((Name_of_your_Activity) getActivity()).helper
On Activity
DbHelper helper = new DbHelper(this);
Inside fragment for kotlin sample would help someone
textViewStatus.setTextColor(ContextCompat.getColor(context!!, R.color.red))
if you use databinding;
bindingView.textViewStatus.setTextColor(ContextCompat.getColor(context!!, R.color.red))
Where bindingView is initialized in onCreateView like this
private lateinit var bindingView: FragmentBookingHistoryDetailBinding
bindingView = DataBindingUtil.inflate(inflater, R.layout.your_layout_xml, container, false)
You can use getActivity(), which returns the activity associated with a fragment. The activity is a context (since Activity extends Context).
be careful: getActivity() can return null if it is called before onAttach of the respective fragment.
2.or
The easiest and most precise way to get the context of the fragment that I found is to get it directly from the ViewGroup when you call onCreateView method at least here you are sure not to get null for getActivity():
public class Animal extends Fragment {
Context thiscontext;
@Override
public View onCreateView(LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState)
{
thiscontext = container.getContext();
//...
//...
//...
}
In Kotlin you can use this: requireActivity().applicationContext
Success story sharing
getActivity().getApplicationContext()
in an instance variable when the fragment is created and then use that context whenever you want inside the fragment class. That context will survive fragment detachments.getActivity
has always been available. It'sgetContext
which was added in API 23.