Android: How to Create a Modal Progress "Wheel" Overlay?

Not sure if there is a better way, but you could get the spinner wheel on its own by using a ProgressBar and setting it to be interdeterminate. If you are using an AbsoluteLayout you can put it over other views. This layout should demonstrate this method with XML:

<?xml version="1.0" encoding="utf-8"?>
<AbsoluteLayout android:id="@+id/AbsoluteLayout"
    android:layout_width="fill_parent" android:layout_height="fill_parent"
    xmlns:android="http://schemas.android.com/apk/res/android">
    <ProgressBar android:id="@+id/ProgressBar"
        android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:indeterminate="true" android:indeterminateOnly="true"
        android:isScrollContainer="true" android:layout_x="100dip"
        android:layout_y="10dip" android:soundEffectsEnabled="true"></ProgressBar>
    <TextView android:layout_width="fill_parent"
        android:layout_height="wrap_content" android:text="@string/hello"
        android:layout_gravity="center_horizontal" android:gravity="center_horizontal"
        android:layout_y="25dip" />
</AbsoluteLayout>

In order to create a full screen progress on a darkened background I use a FrameLayout and set the visibility of the RelativeLayout to VISIBLE when required or GONE when the long operation is done:

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

    <ScrollView 
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

        <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentTop="true"
        android:orientation="vertical"
        android:padding="3dip" >

            <!-- Your regular UI here -->

    </LinearLayout>
   </ScrollView>

   <RelativeLayout
       android:id="@+id/relativelayout_progress"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       android:visibility="gone"
       android:background="#aa000022" >

       <ProgressBar 
           android:layout_centerInParent="true"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:indeterminateOnly="true" />

    </RelativeLayout>
</FrameLayout>

Klarth's solution worked for me, thanks!

In my case I used the layout_gravity for center placement of the progress_indicator, rather than using explicit coordinates.

    <ProgressBar android:id="@+id/pb"
        android:layout_width="40dp" 
        android:layout_height="40dp"
        android:indeterminate="true" 
        android:indeterminateOnly="true"
        android:isScrollContainer="true" 
        android:layout_gravity="center_vertical|center_horizontal"
        android:soundEffectsEnabled="false"
        />