Flutter AppBar添加白色边框

Question

Trying to create a custom navigation bar at the top of the screen. Currently with the below code I'm getting a white border around my nav bar. Anyway to fix this? I've evaluated it's not the actual header as if it's in the body of the scaffold it fits 100% to the size.

Widget build(BuildContext context) {
Widget body = Body();
Widget header = Header();

return new Scaffold(

    appBar: new PreferredSize(
      preferredSize: Size(1000.0, 1000.0),
      child: new Card(
        child: header
      )),
    body: ListView(
      children: [
        body
      ],
    )
  );

Answer 1

Card widget by default sets all its margins to 4.0. Override that value in your build method and you should be good:

child: new Card(
  margin: EdgeInsets.zero,
  child: header
)