damndaniel2612 :
I wanted to have the Text of a TextView changed to whatever the username of the active user is, but the method updateUI() always returns this error:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.cocko.industries.einkaufshelfer.shopper, PID: 18704
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.cocko.industries.einkaufshelfer.shopper/com.cocko.industries.einkaufshelfer.shopper.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' 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 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at com.cocko.industries.einkaufshelfer.shopper.MainActivity.updateUI(MainActivity.java:203)
at com.cocko.industries.einkaufshelfer.shopper.MainActivity.onCreate(MainActivity.java:76)
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)
So what's the problem? It seems to me as if the TextView can't be found and is therefore null. But why? And how can I fix that? Below you can find the MainActivity class with the onCreate and updateUI method and the fragment that I used.
public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {
private DrawerLayout drawer;
private NavigationView nav_view;
private FirebaseAuth mAuth;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
mAuth = FirebaseAuth.getInstance();
nav_view = findViewById(R.id.nav_view);
nav_view.setNavigationItemSelectedListener(this);
drawer = findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(this, drawer, toolbar, R.string.nav_drawer_open, R.string.nav_drawer_close);
drawer.addDrawerListener(toggle);
toggle.syncState();
try {
Intent intent = getIntent();
if (intent.getStringExtra("activity").equals("register")) {
getSupportFragmentManager().beginTransaction().replace(R.id.framgment_container, new UserprofileFragment()).commit();
}
} catch (NullPointerException noIntentExtra) {
getSupportFragmentManager().beginTransaction().replace(R.id.framgment_container, new AssignmentsFragment()).commit();
}
if (mAuth.getCurrentUser() != null){
updateUI();
}
}
And the updateUI function is as follows.
public void updateUI() {
TextView textView = findViewById(R.id.textview_assignemntsheader);
textView.setText("Test");
}
Here's the layout for my fragment, that is fragment_assignments.xml:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="@+id/textview_assignemntsheader"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:text="@string/textview_assigmentsHeader"
android:textAlignment="center"
android:textAppearance="@style/TextAppearance.AppCompat.Display1"
android:textStyle="bold"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<ScrollView
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_marginStart="8dp"
android:layout_marginTop="16dp"
android:layout_marginEnd="8dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/textview_assignemntsheader">
<LinearLayout
android:id="@+id/linearlayout_assignments"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
</LinearLayout>
</ScrollView>
</androidx.constraintlayout.widget.ConstraintLayout>
And the layout for my activity is activity_main.xml:
<?xml version="1.0" encoding="utf-8"?>
<androidx.drawerlayout.widget.DrawerLayout 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:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context=".MainActivity"
tools:openDrawer="start">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<androidx.appcompat.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="@color/colorPrimary"
android:elevation="4dp"
android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />
<FrameLayout
android:id="@+id/framgment_container"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
<com.google.android.material.navigation.NavigationView
android:id="@+id/nav_view"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
app:headerLayout="@layout/nav_header"
app:menu="@menu/menu" />
</androidx.drawerlayout.widget.DrawerLayout>
oussama-zaoui :
you can't find your textView in MainActivity because it is not in the main_activity.xml, so updateUI should be in UserProfile Fragment.
in OnCreateView
try this :
View view = inflater.inflate(R.layout.fragment_assignments, container,false);
TextView text=view.findViewById(R.id.textview_assignemntsheader);
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