The cursor and text in this picture are what I want

But my demo looks like this.The text and cursor are small and not filled
code
TextEditingController searchController = new TextEditingController();
FocusNode focusNode = new FocusNode();
// other code
TextField(
key: Key("buy_subject_input"),
autofocus: true,
focusNode: focusNode,
cursorColor: Colours.default_color,
decoration: InputDecoration(
hintText: 'search',
hintStyle: TextStyle(
color: Colours.hint_text_color,
),
prefixIcon: Icon(
Icons.search,
color: Colours.hint_text_color,
),
fillColor: Colors.white,
filled: true,
border: UnderlineInputBorder(
borderSide: BorderSide.none,
borderRadius: BorderRadius.all(Radius.circular(5)),
),
),
controller: searchController,
),
//other code
