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);
}
This question is related to
java
android
android-fragments
android-context
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
.
With API 29+ on Kotlin, I had to do
activity?.applicationContext!!
An example would be
ContextCompat.getColor(activity?.applicationContext!!, R.color.colorAccent),
@Override
public void onAttach(Activity activity) {
// TODO Auto-generated method stub
super.onAttach(activity);
context=activity;
}
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();
Another alternative approach is:
You can get the context using:
getActivity().getApplicationContext();
requireContext() method is the simplest option
requireContext()
Example
MyDatabase(requireContext())
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));
You have different options:
getActivity()
, since this is a Context
.getContext()
.If you don't need to support old versions then go with getContext()
.
to get the context inside the Fragment will be possible using getActivity()
:
public Database()
{
this.context = getActivity();
DBHelper = new DatabaseHelper(this.context);
}
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;
}
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)
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();
}
}
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);
}
}
On you fragment
((Name_of_your_Activity) getActivity()).helper
On Activity
DbHelper helper = new DbHelper(this);
In kotlin just use activity
instead of getActivity()
getActivity()
is a child of Context so that should work for you
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()
.
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.
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.
You can call getActivity()
or,
public void onAttach(Context context) {
super.onAttach(context);
this.activity = (CashActivity) context;
this.money = this.activity.money;
}
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();
/* ... */
}
}
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)
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;
}
}
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
,
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.
getContext() method helps to use the Context of the class in a fragment activity.
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))
You can use 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!
getActivity()
or getContext
in Fragment.Documentation
/**
* Return the {@link FragmentActivity} this fragment is currently associated with.
* May return {@code null} if the fragment is associated with a {@link Context}
* instead.
*
* @see #requireActivity()
*/
@Nullable
final public FragmentActivity getActivity() {
return mHost == null ? null : (FragmentActivity) mHost.getActivity();
}
and
/**
* Return the {@link Context} this fragment is currently associated with.
*
* @see #requireContext()
*/
@Nullable
public Context getContext() {
return mHost == null ? null : mHost.getContext();
}
Check always if(getActivity!=null)
because it can be null when fragment is not attached to activity. Sometimes doing long operation in fragment (like fetching data from rest api) takes some time. and if user navigate to another fragment. Then getActivity will be null. And you will get NPE if you did not handle it.
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.
Also you can use:
inflater.getContext();
but I would prefer to use
getActivity()
or
getContext
Source: Stackoverflow.com