How to create a horizontal loading progress bar?

For using the new progress bar

style="?android:attr/progressBarStyleHorizontal"

for the old grey color progress bar use

style="@android:style/Widget.ProgressBar.Horizontal"

in this one you have the option of changing the height by setting minHeight

The complete XML code is:

<ProgressBar
    android:id="@+id/pbProcessing"
    style="?android:attr/progressBarStyleHorizontal"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_below="@+id/tvProcessing"
    android:indeterminateOnly="true"/>

indeterminateOnly is set to true for getting indeterminate horizontal progress bar

Just add a STYLE line and your progress becomes horizontal:

<ProgressBar
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/progress"
        android:layout_centerHorizontal="true"      
        android:layout_centerVertical="true"      
        android:max="100" 
        android:progress="45"/>

It is Widget.ProgressBar.Horizontal on my phone, if I set android:indeterminate="true"