Question

I am trying to make a listview in android but i got some troubles.

This is the code:

public class MainActivity extends Activity
{
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        String[] items = {"red", "blue", "green"};

        ListView listView = (ListView) findViewById(R.id.list);
        listView.setAdapter(new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1, items));
    }
}

And this the xml file:

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

    <Button
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:text="Agregar Tarea"
        android:id="@+id/btn" />

    <ListView
        android:layout_width="match_parent"
        android:layout_height="wrap_content" 
        android:layout_below="@+id/list" />

</RelativeLayout>

The logcat says that there is a NullPointerException in line 21, this line:

ListView listView = (ListView) findViewById(R.id.list);

But I dont know why 🙁

I want to do the list view this way becouse if I use listactivity the header/footers is not fixed.

Answer 1

Try change this

android:layout_below="@+id/list"

to this:

android:id="@+id/list"