Flutter TextField设置高度并且自动换行，圆角边框去除下划线

核心代码

  child: new TextField(
                    controller: _mnemonicController,
                    keyboardType: TextInputType.multiline,
                    maxLines: 10,
                    minLines: 1,

          Container(
                  margin: EdgeInsets.only(left: 18.0, right: 18.0, top: 15),
                  height: 150,
                  width: MediaQuery.of(context).size.width,
                  decoration: new BoxDecoration(
                      border: new Border.all(
                          color: ColorsBase.color_gray_broder, width: 0.5),
                      borderRadius: new BorderRadius.circular((10.0))),

                  child: new TextField(
                    controller: _mnemonicController,
                    keyboardType: TextInputType.multiline,
                    maxLines: 10,
                    minLines: 1,
                    onChanged: (value) {
    
                      setState(() {
    });
                    },
                    autofocus: false,
                    decoration: InputDecoration(
                      enabledBorder: new UnderlineInputBorder(
                        borderSide: BorderSide.none,
                      ),
                      focusedBorder: new UnderlineInputBorder(
                        borderSide: BorderSide.none,
                      ),
                      contentPadding:
                          EdgeInsets.symmetric(vertical: 10, horizontal: 10),
                      hintText:
                          S.of(context).string_wallet_enter_mnemonic,
                      hintStyle: TextStyle(fontSize: 13,color: ColorsBase.text_gray),
                      counterText: '',
                    ),
                  ),
                ),