Null Pointer Exception for button in fragment

Question

I have been trying to set an OnClickListener in a fragment, for a button in my activity's layout. However, I keep getting a null pointer exception when using findViewById() for the button. I think I am correctly using getActivity().findViewById() correctly, because I use it for R.id.chipGroup (which is from the same LinearLayout as the button) elsewhere in my code and it works fine.

In the Fragment:

public View onCreateView(@NonNull LayoutInflater inflater,
                             @Nullable ViewGroup container,
                             @Nullable Bundle savedInstanceState) {

        View layout = inflater.inflate(R.layout.fragment_maps, container, false);

        Button connButton = (Button)getActivity().findViewById(R.id.connections_button);
        connButton.setOnClickListener(this::onClick);

        return layout;
}

Activity XML

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MapActivity">

    <ScrollView
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/location_editText">

        <LinearLayout
            android:id="@+id/map_linearLayout"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">

            <com.google.android.material.chip.ChipGroup
                android:id="@+id/chipGroup"
                android:layout_width="match_parent"
                android:layout_height="match_parent" />

            <Button
                android:id="@+id/connections_button"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="Add a Connection" />

        </LinearLayout>
    </ScrollView>

Log

     Caused by: android.view.InflateException: Binary XML file line #72 in com.example.app3:layout/activity_map: Binary XML file line #72 in com.example.app3:layout/activity_map: Error inflating class fragment
     Caused by: android.view.InflateException: Binary XML file line #72 in com.example.app3:layout/activity_map: Error inflating class fragment
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
        at com.example.app3.MapsFragment.onViewCreated(MapsFragment.java:175)
        at androidx.fragment.app.FragmentManagerImpl.ensureInflatedFragmentView(FragmentManagerImpl.java:1144)
        at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:851)
        at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:1133)
        at androidx.fragment.app.FragmentManagerImpl.addFragment(FragmentManagerImpl.java:1393)
        at androidx.fragment.app.FragmentManagerImpl.onCreateView(FragmentManagerImpl.java:3205)
        at androidx.fragment.app.FragmentController.onCreateView(FragmentController.java:134)
        at androidx.fragment.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:357)
        at androidx.fragment.app.FragmentActivity.onCreateView(FragmentActivity.java:336)
        at android.view.LayoutInflater.tryCreateView(LayoutInflater.java:1067)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:995)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:959)
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:1121)
        at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1082)
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:1124)
        at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1082)
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:1124)
        at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1082)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:680)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:532)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:479)
        at androidx.appcompat.app.AppCompatDelegateImpl.setContentView(AppCompatDelegateImpl.java:696)
        at androidx.appcompat.app.AppCompatActivity.setContentView(AppCompatActivity.java:170)
        at com.example.app3.MapActivity.onCreate(MapActivity.java:27)
        at android.app.Activity.performCreate(Activity.java:8000)
        at android.app.Activity.performCreate(Activity.java:7984)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3422)
2021-05-06 19:44:50.450 11225-11225/com.example.app3 E/AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)

Sajad Hosseini · Answer 1 · 2021-05-06T23:52:15.927

0

Replace this:

Button connButton = (Button)getActivity().findViewById(R.id.connections_button);

with

Button connButton = (Button)layout.findViewById(R.id.connections_button);

And be sure you import fragment v4:

import android.support.v4.app.Fragment;

edited May 06 '21 at 23:52

answered May 06 '21 at 23:28

Sajad Hosseini

135
8

If your app is open source please attach your link. – Sajad Hosseini May 06 '21 at 23:31
It is not open source, is there any particular part of the app that you want me to add? – user May 06 '21 at 23:40
Log after inflate and be sure your fragment works fine. – Sajad Hosseini May 06 '21 at 23:43
the fragment works if i remove those two lines about the button – user May 06 '21 at 23:47
Update answer please check again. – Sajad Hosseini May 06 '21 at 23:53
Would importing androidx.fragment.app.Fragment not work? If im not mistaken, androidx replaced the older packages – user May 07 '21 at 00:01
Yeah, androidx is ok. Check this link [link](https://stackoverflow.com/questions/19874882/android-view-inflateexception-binary-xml-file-error-inflating-class-fragment?page=1&tab=oldest#tab-top) – Sajad Hosseini May 07 '21 at 00:07
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/232063/discussion-between-sajad-hosseini-and-user). – Sajad Hosseini May 07 '21 at 00:23

score 0 · Answer 2 · answered May 06 '21 at 23:31

0

The Activity has not been created yet. Try to move findViewById and setOnClickListener to onViewCreated.

answered May 06 '21 at 23:31

hata

11,633
6
46
69

I still get the same message in the logcat: Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference – user May 06 '21 at 23:35

user · Answer 3 · 2021-05-07T00:29:31.317

I don't know why, but putting a new OnClickListener in the OnMapReadyCallback seems to work.

 private OnMapReadyCallback callback = new OnMapReadyCallback() {
        @Override
        public void onMapReady(GoogleMap gMap) {
               Button connButton = getActivity().findViewById(R.id.connections_button);
               connButton.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    connButton.setText("works");
                }
            });
        }
}

Null Pointer Exception for button in fragment

3 Answers3