How to make transparent gradient?

You can try the following code :

<gradient android:startColor="#hex_of_any_color" android:endColor="#00000"/>

android:background="#00000000" android:cacheColorHint="#00000000"

this will make is transparent however, this is to make it a full transparency...

Just use an 8-digit color value, e.g. #FFF8F8F6, where the first two characters are the alpha value. FF being fully opaque, and 00 being fully transparent.