How to set shape's opacity?

Question

I already know how to set the opacity of the background image but I need to set the opacity of my shape object.

In my Android app, I have it like this:

Answer 1

use this code below as progress.xml:

where:

• "progress" is current progress before the thumb and "secondaryProgress" is the progress after thumb.
• color="#00000000" is a perfect transparency
• NOTE: the file above is from default android res and is for 2.3.7, it is available on android sources at: frameworks/base/core/res/res/drawable/progress_horizontal.xml. For newer versions you must find the default drawable file for the seekbar corresponding to your android version.

after that use it in the layout containing the xml:

you can also customize the thumb by using a custom icon seek_thumb.png:

android:thumb="@drawable/seek_thumb"