We have in our project a keyboard with "Key" elements, this Key elements have attributes such as android:codes="119", android:keyLabel="w" and so on.
My question is how can I include an custom attribute like a "android:alternativeKeyLabel" to do something else.
You can create custom attributes for your own classes that extend View or a subclass. The process is documented in the "Creating a View Class" section of the Android Dev Guide under the heading "Define Custom Attributes":
https://developer.android.com/training/custom-views/create-view#customattr
android:keyLabel is one of many XML attribute used by the Keyboard.Key class for each key on your keyboard. android:keyLabel is what you want to label the key with (like a "w" as in above). The attributes are pre-defined for the class. The "w" isn't but android:keyLabel is. If you could create android:alternativeKeyLabel what would you expect the class to do with it? I think maybe you should try to explain further what you are trying to accomplish.
