Android: Adding static header to the top of a ListActivity

findViewById() only works to find subviews of the object View. It will not work on a layout id.

You'll have to use layout inflater to convert the xml to it's corresponding View components. Something like this:

ListView lv = getListView();
LayoutInflater inflater = getLayoutInflater();
View header = inflater.inflate(R.layout.header, lv, false);
lv.addHeaderView(header, null, false);

I'm not sure why your code wasn't just throwing an error. findViewById() was probably just returning null, and so no header was added to your list.

Here is the simpliest sollution:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
 xmlns:android="http://schemas.android.com/apk/res/android"
 android:orientation="vertical"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent"
 android:background="@color/background">
 <include layout="@layout/actionbar"/>
   <ListView
    android:id="@+id/tasklist_TaskListView"
    android:layout_width="fill_parent"
    android:layout_height="0dip"
    android:layout_weight="1"
    android:textColor="@color/baseFont"/>
   <include layout="@layout/bottombar"/>
</LinearLayout>

or

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
 xmlns:android="http://schemas.android.com/apk/res/android"
 android:orientation="vertical"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent"
 android:background="@color/background">
   <Button 
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"/>
   <ListView
    android:id="@+id/tasklist_TaskListView"
    android:layout_width="fill_parent"
    android:layout_height="0dip"
    android:layout_weight="1"
    android:textColor="@color/baseFont"/>
   <Button 
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"/>

</LinearLayout>

instead of button you can add another horizontal linear layout