Android custom keyboard shift key

How can i implement the Shift key functionality for android custom keyboard, i want to change the keys from caps to small and small to caps while clicking the Shift key, for me it is coming but while typing the messages texts are only in smalls, and also i need separate background for each key, for this purpose me implemented android:keyicon instead of android:keylabel attribute but while doing this the problem will arise when changing to small from caps by pressing he Shift key, any idea please help, thanks very much for your efforts