Getting nullpointerexception even after giving right reference. Please see details

Question

I'm trying to set the name and email in NavigationView after fetching it from the database.

Here's how I have given reference of NavigationView in onCreate() method:

navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);

But, I'm still getting this error: Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.support.design.widget.NavigationView.getHeaderView(int)' on a null object reference at com.abc.xyz.MainActivity.fetchDataFromProviderProvided(MainActivity.java:689)

Here's fetchDataFromProviderProvided() method:

public void fetchDataFromProviderProvided() {
        if (authData != null) {
            swipeRefreshLayout.setRefreshing(false);
            if (authData.getProvider().equals("google")) {
                fetchDataFromGoogle();
            } else if (authData.getProvider().equals("facebook")) {
                onFacebookAccessTokenChange(AccessToken.getCurrentAccessToken());
            } else {

                // DO SOMETHING TO FETCH USER'S NAME

                String Uid = authData.getUid();

                Log.d("Uid:", Uid);

                Firebase userNameRef = mFirebaseRef.child(Uid + "/userName");

                Log.d("userName", String.valueOf(userNameRef));

                emailImage = (String) authData.getProviderData().get("profileImageURL");

                // error on the line below
                View imageView = navigationView.getHeaderView(0);
                //
                userImage = (ImageView) imageView.findViewById(R.id.userImage);

                new emailProfilePicAsync().execute(authData.getUid());

                View nameView = navigationView.getHeaderView(0);
                userName = (TextView) nameView.findViewById(R.id.userName);

                userNameRef.addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {
                        userName.setText(String.valueOf(dataSnapshot.getValue()));
                    }

                    @Override
                    public void onCancelled(FirebaseError firebaseError) {

                    }
                });

                emailName = userNameText;
                emailEmail = (String) authData.getProviderData().get("email");

                View emailView = navigationView.getHeaderView(0);
                userEmail = (TextView) emailView.findViewById(R.id.userEmail);
                userEmail.setText(emailEmail);

//                System.out.println(post.getUserName());
//                System.out.println(post.getUserEmail());
            }

            dataLoadingCompleteProgressDialog = ProgressDialog.show(MainActivity.this, "",
                    "Fetching user's info...", true);

            if (dataLoadingCompleteProgressDialog.isShowing()) {
                Handler handler = new Handler();
                handler.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        checkIfDataIsFetched();
                        dataLoadingCompleteProgressDialog.dismiss();
                    }
                }, 5500);
            }

        } else {

        }
    }

Here's activity_main.xml file's code:

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
    android:id="@+id/drawer_layout"
    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"
    android:fitsSystemWindows="true"
    tools:openDrawer="start">

    <include
        layout="@layout/app_bar_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

    <android.support.design.widget.NavigationView
        android:id="@+id/nav_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:fitsSystemWindows="true"
        app:headerLayout="@layout/nav_header_main"
        app:menu="@menu/activity_main_drawer"/>

</android.support.v4.widget.DrawerLayout>

Here's complete stacktrace:

FATAL EXCEPTION: main
                                                                               Process: com.abc.xyz, PID: 19072
                                                                               java.lang.RuntimeException: Unable to start activity ComponentInfo{com.abc.xyz/com.abc.xyz.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.support.design.widget.NavigationView.getHeaderView(int)' on a null object reference
                                                                                   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
                                                                                   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
                                                                                   at android.app.ActivityThread.-wrap11(ActivityThread.java)
                                                                                   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
                                                                                   at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                                   at android.os.Looper.loop(Looper.java:148)
                                                                                   at android.app.ActivityThread.main(ActivityThread.java:5417)
                                                                                   at java.lang.reflect.Method.invoke(Native Method)
                                                                                   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
                                                                                Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.support.design.widget.NavigationView.getHeaderView(int)' on a null object reference
                                                                                   at com.abc.xyz.MainActivity.fetchDataFromProviderProvided(MainActivity.java:694)
                                                                                   at com.abc.xyz.MainActivity.onCreate(MainActivity.java:217)
                                                                                   at android.app.Activity.performCreate(Activity.java:6237)
                                                                                   at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
                                                                                   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
                                                                                   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
                                                                                   at android.app.ActivityThread.-wrap11(ActivityThread.java) 
                                                                                   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
                                                                                   at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                                   at android.os.Looper.loop(Looper.java:148) 
                                                                                   at android.app.ActivityThread.main(ActivityThread.java:5417) 
                                                                                   at java.lang.reflect.Method.invoke(Native Method) 
                                                                                   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                                                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 

Please let me know what's wrong here.

Sorry, for bad formatting of the question. I'm still a beginner here.

Answer 1

Add this line:

View header = navigationView.getHeaderView(0);

navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
View header = navigationView.getHeaderView(0);

Answer 2

Make sure, you Initialise the navigationView before the call for method fetchDataFromProviderProvided() is done.

To prevent such Mistakes, and for better Maintainability of code make use of the ButterKnife library. This is pretty simple to use.

in onCreate() method call Butterknife.bind() and to initialise any View Objects do the following :

@Bind(R.id.nav_view)
NavigationView navigationView;

Hope this helps.

Reference Butterknife