Question

I have a layout called view.xml which contains a View called view_related. Basically, in my dictionary app, if there are related words to an entry, I will replace view_related with a LinearLayout that contains a header “Related entries” and a bunch of TextViews representing every related word.

I keep getting a NullPointerException everytime I’m adding a TextView to the LinearLayout in my Activity‘s onCreate() method, and I don’t understand why though my code looks pretty straightforward.

view.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <TextView android:id="@+id/view_header"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="12pt"
        android:textColor="#fff"
        android:textStyle="bold"
        android:background="#990011"
        android:padding="10dp"
        android:text="lalala word"
        />

    <ScrollView android:id="@+id/view_description"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/view_header">
        <LinearLayout android:id="@+id/view_description_content"
            android:orientation="vertical"
            android:layout_width="match_parent"
            android:layout_height="wrap_content">
            <TextView android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:padding="20dp"
                android:text="@string/demo_definition"
                />
                <!-- THIS WILL BE REPLACED -->
            <View android:id="@+id/view_related"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"></View>
        </LinearLayout>
    </ScrollView>

</RelativeLayout>

view_related.xml, the LinearLayout that will replace the View element in view.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/view_related_entries"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
    <TextView android:id="@+id/view_related_header"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="5dp"
        android:textColor="#fff"
        android:textStyle="bold"
        android:textSize="7pt"
        android:background="#000"
        android:text="Related entries"
        />
    <LinearLayout android:id="@+id/view_related_list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        >
    </LinearLayout>
</LinearLayout>

And finally, the onCreate method, which for now assumes the related entries are “Hello” and “Goodbye:”

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.view);

    LinearLayout ll = (LinearLayout) findViewById(R.id.view_related_list);
    TextView tv = new TextView(this);
    tv.setText("Hello");
    ll.addView(tv); // NULL POINTER EXCEPTION

    tv = new TextView(this);
    tv.setText("Goodbye");
    ll.addView(tv);

    LayoutInflater li = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
    View view = findViewById(R.id.view_related);
    ViewGroup parent = (ViewGroup) view.getParent();
    int index = parent.indexOfChild(view);
    parent.removeView(view);
    View llview = li.inflate(R.id.view_related_entries, parent, false);
    parent.addView(llview, index);
}

Answer 1

the line (LinearLayout ll = (LinearLayout) findViewById(R.id.view_related_list);) will search for view_related_list in view.xml, as in the line before that is the view you are using..

You need to inflate view_related.xml first and then get the view from it..