Question

when i implements textwatcher, a error occur

Syntax error on token "implements", extends expected

my code is

import android.text.TextWatcher;
public interface Testing implements TextWatcher{

}

why i need to use extends?

Answer 1

You’re not implementing TextWatcher – you’re creating a new interface which extends it.

So you would write:

public interface Testing extends TextWatcher

or

public class Testing implements TextWatcher

You haven’t said what you’re really trying to do, so we can’t tell whether you should actually be declaring a class, or just declaring a new interface which extends TextWatcher.

See section 9.1.3 of the JLS for more details of declaring one interface to extend another.