Android textwatcher倒计时

Question

如何在打字过程中将textwatcher从250减少到0？ android:maxLength="250"已设置，因此不会低于0.

 et_Notes = (EditText) dialog_list.findViewById(R.id.EditText_Notes);
 tvC = (TextView)dialog_list.findViewById(R.id.TextViewCounter);

    final TextWatcher mTextEditorWatcher = new TextWatcher() {
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
        }

        public void onTextChanged(CharSequence s, int start, int before, int count) {

           tvC.setText(String.valueOf(s.length()));
        }

        public void afterTextChanged(Editable s) {

        }
    };

    et_Notes.addTextChangedListener(mTextEditorWatcher);

Answer 1

将其应用于InputFilter.LengthFilter并将限制设置为250个字符，并在方法afterTextChanged中将计数器设置为250 - 文本的长度