如何收听EditText？

如何收听EditText？

文本观察器的示例代码

your_edittext.addTextChangedListener(new InputValidator());    private class InputValidator implements TextWatcher {        public void afterTextChanged(Editable s) {        } public void beforeTextChanged(CharSequence s, int start, int count,     int after) {        } public void onTextChanged(CharSequence s, int start, int before,     int count) {        }        }    }