TextView.setText() showing NPE even though the id is correct inside xml layout file-CodePudding

This is my XML code (activity_homepage.xml):

 <android.support.design.widget.NavigationView
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    android:id="@ id/nav_view"
    app:headerLayout="@layout/nav_header"
    app:menu="@menu/drawer_menu"/>

nav_header.xml:

 <LinearLayout 
     xmlns:android="http://schemas.android.com/apk/res/android"
     android:orientation="vertical"
     android:layout_width="match_parent"
     android:layout_height="176dp"
     android:background="@color/design_default_color_primary_dark"
     android:gravity="bottom"
     android:padding="16dp"
     android:theme="@style/ThemeOverlay.AppCompat.Dark">

     <ImageView
         android:layout_width="68dp"
         android:layout_height="58dp"
         android:layout_marginBottom="10dp"
         android:src="@drawable/ic_action_name"/>
     <TextView
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:paddingTop="8dp"
         android:text="Null"
         android:id="@ id/user"
         android:textAppearance="@style/TextAppearance.AppCompat.Body1"
         android:paddingLeft="8dp"/>

 </LinearLayout>

And this is my java code:

@Override
TextView txt;
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_homepage);
    txt = findViewById(R.id.user);
    Bundle extras = getIntent().getExtras();
    if (extras != null) {
        String value = extras.getString("Name");
        txt.setText(value); //throws NullPointerException
    }
}

I've double checked the id, it's correct. Then why the NullPointerException?

EDIT: Tried to fetch the header from the navigation view like this:

NavigationView navigationView = findViewById(R.id.nav_view);
View header = navigationView.getHeaderView(1);
txt = header.findViewById(R.id.user);

I still get NPE in the line navigationView.getHeaderView(1);

CodePudding user response：

navigationView.getHeaderView( 0 );

How about 0 ?

CodePudding user response：

I had done such a silly mistake :p

I tried fetching the header before setContentView(). That's why I was getting NPE. The following code resolved the issue:

    setContentView(R.layout.activity_homepage);
    NavigationView navigationView = findViewById(R.id.nav_view);
    View header = navigationView.getHeaderView(0);