[android] Your content must have a ListView whose id attribute is 'android.R.id.list'

I have created an xml file like this:

<?xml version="1.0" encoding="utf-8"?>
<ListView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/list" >
</ListView>

and an activity:

public class ExampleActivity extends ListActivity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {   
        super.onCreate(savedInstanceState);
        setContentView(R.layout.mainlist);
    }
}

As you see, I have not done anything else. But I'am getting the error:

Your content must have a ListView whose id attribute is 'android.R.id.list'

Even though I have the android:id="@+id/list" line in my xml.

What is the problem?

You should have one listview in your mainlist.xml file with id as @android:id/list

<ListView
    android:id="@android:id/list"
    android:layout_height="wrap_content"
    android:layout_height="fill_parent"/>

<ListView android:id="@android:id/list"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"/>

this should solve your problem

Exact way I fixed this based on feedback above since I couldn't get it to work at first:

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<ListView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@android:id/list"
>
</ListView>

MainActivity.java:

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

preferences.xml:

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" >
<PreferenceCategory
    android:key="upgradecategory"
    android:title="Upgrade" >
    <Preference
        android:key="download"
        android:title="Get OnCall Pager Pro"
        android:summary="Touch to download the Pro Version!" />
</PreferenceCategory>
</PreferenceScreen>

One other thing that affected me: If you have multiple test devices, make sure you are making changes to the layout used by the device. In my case, I spent a while making changes to xmls in the "layout" directory until I discovered that my larger phone (which I switched to halfway through testing) was using xmls in the "layout-sw360dp" directory. Grrr!

<ListView android:id="@id/android:list"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:drawSelectorOnTop="false"
        android:scrollbars="vertical"/>

Inherit Activity Class instead of ListActivity you can resolve this problem.

public class ExampleActivity extends Activity  {

    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.mainlist);
    }
}