Transparent LinearLayout on Android

I have the folowing layout:

enter image description here

I want to make transparent the transparent_layout but i can't do it.

Already tried settings the background programmatically with the color: Color.TRANSPARENT but it seems it doesnt work.

Im using Android 2.3.3 SDK with SherlockActionBar.

Is there any way to set that layout to transparent?

How do I make Constraintlayout transparent?

If you add this line to the Constraint Layout xml it will become transparent: android:background="@android:color/transparent" . This will make the background see through and show what ever is bellow or overlapping.

Depending upon the degree of opacity you like, set the background color like

        android:background="#00ffffff"

The first two digits are for opacity level, (aka alpha) that varies from 00 to ff (fully-transparent to fully-opaque), the remaining digits are for the desired background color. If you keep first 2 digits zero (00), then whatever color you choose for the remaining digits, doesn't matter.