Why Getcontext() in Fragment Sometimes Returns Null

Why getContext() in fragment sometimes returns null?

First of all, as you can see on this link, the method onCreateView() inside the fragment's lifecycle comes after onAttach(), so you should have already a context at that point. You may wonder, why does getContext() return null then? the problem lies on where you are creating your adapter:

App.getApiService().getLatestNews().enqueue(new Callback<LatestNews>() {
        @Override
        public void onResponse(Call<LatestNews> call, Response<LatestNews> response) {
            if (response.isSuccessful() && response.body().isSuccessfull()){
                adapter = new LastNewsRVAdapter(getContext(), response.body().getData(), sideBanner);
                rvLatestNews.setAdapter(adapter);
                tvSonkuKabar.setVisibility(View.VISIBLE);
            }
        }

        @Override
        public void onFailure(Call<LatestNews> call, Throwable t) {

        }
    });

Though you are specifying a callback in onCreateView(), that does not mean the code inside that callback will run at that point. It will run and create the adapter after the network call is done. With that in mind, your callback may run after that point in the lifecycle of the fragment. What I mean is that the user can enter that screen (fragment) and go to another fragment or return to the previous one before the network request finishes (and the callback runs). If that happens, then getContext() could return null if the user leaves the fragment (onDetach() may have been called).

Besides, you can have memory leaks also, in case the activity is destroyed before your network request finishes. So you have two issues there.

My suggestions to solve those issues are:

1. in order to avoid the null pointer exception and the memory leak, you should cancel the network request when the onDestroyView() inside the fragment is being called (retrofit returns an object that can cancel the request: link).

2. Another option that will prevent the null pointer exception is to move the creation of the adapter LastNewsRVAdapter outside the callback and keep a reference to it in the fragment. Then, use that reference inside the callback to update the content of the adapter: link

Android: getContext() in Fragment returns null only when leaving over the Back Button

When pressing the back button, the fragment is no longer attached to the activity, so getContext() returns null.

You can check if your fragment is still added to the activity and then call your getSystemServicelike below

if (isAdded()) {
   getContext().getSystemService(Context.ALARM_SERVICE)
}

getContext() method returns null in fragment. Is it a good idea to keep the context in a variable? I want to understand the pros and cons

getActivity() and getContext() both will return null if your fragment is not attached to an activity/context. If they are returning null, I won't suggest using any previously stored value as the stored context may have been detached and can lead to memory leaks.

Generally, you get a context after the fragment is attached. You can store the context in the onAttach(Context) callback.

@Override
public void onAttach(Context context) {
    super.onAttach(context);
    this.context = context;
}

However, be sure to set it to null whenever the fragment gets detached to avoid memory leaks.

@Override
public void onDetach() {
    this.activity = null;
    super.onDetach();
}

There are no cons of storing the context in a variable that I can think of except you need to be careful about fragment state changes. The onDetach() call takes care of that.

getActivity() returns null in Fragment function

commit schedules the transaction, i.e. it doesn't happen straightaway but is scheduled as work on the main thread the next time the main thread is ready.

I'd suggest adding an

onAttach(Activity activity)

method to your Fragment and putting a break point on it and seeing when it is called relative to your call to asd(). You'll see that it is called after the method where you make the call to asd() exits. The onAttach call is where the Fragment is attached to its activity and from this point getActivity() will return non-null (nb there is also an onDetach() call).

Getting null object reference when using getactivity() or getcontext() from fragment to adapter

Your containerViewPager is not a part of your layout fragment_menu.

So your assignment

viewPager = (ViewPager)viewRoot.findViewById(R.id.containerViewPager);

makes viewPager null.

That results in

java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.viewpager.widget.ViewPager.setAdapter(androidx.viewpager.widget.PagerAdapter)' on a null object reference

So you need to give you viewpager a proper id like:

<androidx.viewpager.widget.ViewPager
        android:id="@+id/containerViewPager"
        android:layout_width="355dp"
        android:layout_height="455dp"
        app:layout_constraintTop_toBottomOf="@id/tabLayoutView"
        tools:layout_editor_absoluteX="8dp"/>

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