navigationView setText fatal exception on a null object reference

Question

Ok, so i have been looking around for a solution to this problem and all the solutions I have found are not working. I am trying to change the text of my Sign In Button in my navigationView to Sign Out/Sign In depending on if they are logged in or not and then sending them off to sign in or out if they press the button. For some reason my app is crashing with a fatal exception on a null object reference(some of the Log below). What am I doing wrong?

I created "signInOutText();" so i could try placing it in different spots, it is currently in onResume but i have tried in onCreate as well and originally had it all in onResume. Hopefully I am just overlooking something simple. I cropped out some of my code from MainActivity.java below so it was not so long but let me know if you need to see the full thing.

MainActivity.java

public class MainActivity extends AppCompatActivity {

//Defining Variables
private Toolbar toolbar;
private NavigationView navigationView;
private DrawerLayout drawerLayout;
String category;
MenuItem mPreviousMenuItem;

private ProgressDialog mProgressDialog;

String providerId,uid,name,email;
Uri photoUrl;

private static final String TAG = "MainActivity";

// set name of your preferences list
private static String MY_PREFERENCES = "Settings";
String userNameLoad, emailLoad, profileLoad;
TextView usernameTextView, emailTextView, signInTextView;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // Initializing Toolbar and setting it as the actionbar
    toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    //Initializing NavigationView
    navigationView = (NavigationView) findViewById(R.id.navigation_view);


    //Setting Navigation View Item Selected Listener to handle the item click of the navigation menu
    navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {

        // This method will trigger on item Click of navigation menu
        @Override
        public boolean onNavigationItemSelected(MenuItem menuItem) {

            menuItem.setCheckable(true);
            menuItem.setChecked(true);
            if (mPreviousMenuItem != null) {
                mPreviousMenuItem.setChecked(false);
            }
            mPreviousMenuItem = menuItem;

            //Closing drawer on item click
            drawerLayout.closeDrawers();


            //Check to see which item was being clicked and perform appropriate action
            switch (menuItem.getItemId()){

                //Replacing the main content with fragments                    
                case R.id.home:
                    //code for button
                    break;
                case R.id.cat1:
                    //code for button
                    break;
                case R.id.signIn:                        
                    signInOut();
                    break;
                default:                        
                    break;
            }               

            return true;
        }
    });

    // Initializing Drawer Layout and ActionBarToggle
    drawerLayout = (DrawerLayout) findViewById(R.id.drawer);
    ActionBarDrawerToggle actionBarDrawerToggle = new ActionBarDrawerToggle(this,drawerLayout,toolbar,R.string.openDrawer, R.string.closeDrawer){

        @Override
        public void onDrawerClosed(View drawerView) {
            // Code here will be triggered once the drawer closes as we dont want anything to happen so we leave this blank
            super.onDrawerClosed(drawerView);
        }

        @Override
        public void onDrawerOpened(View drawerView) {
            // Code here will be triggered once the drawer open as we don't want anything to happen so we leave this blank

            super.onDrawerOpened(drawerView);
        }
    };

    //Setting the actionbarToggle to drawer layout
    drawerLayout.setDrawerListener(actionBarDrawerToggle);

    //calling sync state is necessary or else your hamburger icon wont show up
    actionBarDrawerToggle.syncState();
}

private void signInOutText() {

    //Initializing NavigationView
    navigationView = (NavigationView) findViewById(R.id.navigation_view);
    //Get header xml from navigationView
    View header = navigationView.getHeaderView(0);

    //Check if user logged in, change sign in sign out button to correct text
    FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
    if (user != null) {
        signInTextView = (TextView) header.findViewById(R.id.signIn);
        signInTextView.setText(R.string.sign_out);
    } else {
        signInTextView = (TextView) header.findViewById(R.id.signIn);
        signInTextView.setText(R.string.sign_in);
    }
}

private void signInOut(){ 
    //TODO add Code .... if logged in logout
    Intent intent = new Intent(MainActivity.this, ChooserActivity.class);
    startActivity(intent);
    finish();

}

public void setActionBarTitle(String title) {
    if(getSupportActionBar() != null){
        getSupportActionBar().setTitle(title);
    }
}

@Override
public void onResume() {
    super.onResume();
    // Set title
    setActionBarTitle(getString(R.string.app_name));
    signInOutText();
}

}

Log

Unable to resume activity {com.test.app/com.test.app.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void
android.widget.TextView.setText(int)' on a null object reference
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:4156)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:4250)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3361)
at android.app.ActivityThread.access$1100(ActivityThread.java:222)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1795)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7229)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(int)' on a null object reference
at com.test.app.MainActivity.signInOutText(MainActivity.java:203)
at com.test.app.MainActivity.onResume(MainActivity.java:307)
at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1286)
at android.app.Activity.performResume(Activity.java:6987)
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:4145)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:4250) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3361) 
at android.app.ActivityThread.access$1100(ActivityThread.java:222) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1795) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:158) 
at android.app.ActivityThread.main(ActivityThread.java:7229) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)

activity_main.xml

<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/drawer"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context=".MainActivity">

<LinearLayout
    android:layout_height="match_parent"
    android:layout_width="match_parent"
    android:orientation="vertical">
    <include
        layout="@layout/toolbar"
        />
    <FrameLayout
        android:id="@+id/frame"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    </FrameLayout>

</LinearLayout>

<android.support.design.widget.NavigationView
    android:id="@+id/navigation_view"
    android:layout_height="match_parent"
    android:layout_width="wrap_content"
    android:layout_gravity="start"
    app:headerLayout="@layout/header"
    app:menu="@menu/drawer"
    />

menu/drawer.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">

    <group android:id="@+id/drawer_group"
        android:checkable="true">


        <item
            android:id="@+id/home"
            android:checked="false"
            android:icon="@drawable/ic_home_black_24dp"
            android:title="@string/home_string" />
    </group>

    <group android:id="@+id/group_cat"
        android:checkable="true">

        <item
            android:id="@+id/menuCategories"
            android:title="@string/categories_string"
            android:layout_gravity="bottom">

            <menu>

                <item
                    android:id="@+id/cat1"
                    android:checked="false"
                    android:icon="@drawable/ic_inbox_black"
                    android:title="@string/cat1_string" />

            </menu>

        </item>

    </group>


    <group android:id="@+id/group_signInOut"
        android:checkable="true">

        <item
            android:id="@+id/signIn"
            android:checked="false"
            android:icon="@drawable/ic_power_settings_new_black_24dp"
            android:title="@string/sign_in" />

    </group>

</menu>

Thanks for the help!

Answer 1

Ok, so I realized that I was trying to update a menu "item" and not a textView so that made a big difference. Here is the code I used in my signInOutText() to get it to work:

private void signInOutText() {

        // get menu from navigationView
        Menu menu = navigationView.getMenu();

        // find MenuItem you want to change
        MenuItem nav_signIn = menu.findItem(R.id.signIn);

        //Check if user logged in, change sign in/out button to correct text
        FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
        if (user != null) {
            nav_signIn.setTitle(R.string.sign_out);
        } else {
            nav_signIn.setTitle(R.string.sign_in);
        }
    }

I hope it helps someone! Thanks for the help!