您可以将圆角添加到TextField的装饰参数内TextField

new TextField(
  decoration: new InputDecoration(
      border: new OutlineInputBorder(
        borderRadius: const BorderRadius.all(
          const Radius.circular(10.0),
        ),
      ),
      filled: true,
      hintStyle: new TextStyle(color: Colors.grey[800]),
      hintText: "Type in your text",
      fillColor: Colors.white70),
)