EditText 动态获取输入字数,限制长度

//问题最大字数private int num = 30;

etQuestion.addTextChangedListener(new TextWatcher() {    private CharSequence temp;    private int selectionStart;    private int selectionEnd;    @Override    public void beforeTextChanged(CharSequence s, int start, int count, int after) {    }    @Override    public void onTextChanged(CharSequence s, int start, int before, int count) {        temp = s;    }    @Override    public void afterTextChanged(Editable s) {        int number = num - s.length();        tvQuestionNumber.setText(number+"");        selectionStart = etQuestion.getSelectionStart();        selectionEnd = etQuestion.getSelectionEnd();        //删除多余输入的字（不会显示出来）        if (temp.length() > num) {            s.delete(selectionStart - 1, selectionEnd);            etQuestion.setText(s);        }        //设置光标在最后        etQuestion.setSelection(s.length());    }});