Flutter Container: cannot provide both a color and a decoration

Remove the color parameter from the Container and add it to the BoxDecoration:

Widget bodyWidget() {  return Container(    decoration: BoxDecoration(      color: Colors.yellow,      border: Border.all(color: Colors.black),    ),    child: Text("Flutter"),  );}

If you check the Container source code you can see that the color parameter is just used to set the BoxDecoration color if the decoration is null.

decoration = decoration ?? (color != null ? BoxDecoration(color: color) : null),

The error you got is just a helpful reminder of that. Otherwise you would get a strange override (as was apparently the case in the past) or you might not even notice the bug.

The color property is a shorthand for creating a BoxDecoration with a color field. If you are adding a box decoration, simply place the color on the BoxDecoration.

assert(color == null || decoration == null,  'Cannot provide both a color and a decoration\n'  'To provide both, use "decoration: BoxDecoration(color: color)".'),

So if you have used the BoxDecoration in the Container, then you have to remove the color parameter from the Container and add to it in the BoxDecoration

          Container(              decoration: BoxDecoration(                color: Colors.yellow,              ),           // color: Colors.yellow,          )