Declaring a custom android UI element using XML

Question

How do I declare an Android UI element using XML?

Answer 1

Great reference. Thanks! An addition to it:

If you happen to have a library project included which has declared custom attributes for a custom view, you have to declare your project namespace, not the library one's. Eg:

Given that the library has the package "com.example.library.customview" and the working project has the package "com.example.customview", then:

Will not work (shows the error " error: No resource identifier found for attribute 'newAttr' in package 'com.example.library.customview'" ):

Will work: