flutter去掉输入框最大字数显示
https://blog.csdn.net/u012482065/article/details/89017510

new TextField(
    maxLength:11 ,
    enabled:widget.phone == null?true:false,
    keyboardType: TextInputType.number,
    decoration: InputDecoration(
        counterText: "",  // 此处控制最大字符是否显示
        hintText: widget.phone == null ? '手机号' : widget.phone,
        hintStyle: TextStyle(
            fontSize: 14,
            color: AppColors.colorGrayText,
        ),
        border: InputBorder.none,
    ),
    controller: _phoneContro,   
);