Body size & margins not being respected inside NestedScrollView

Question

I'm trying to understand why on the code bellow "Containers" in this case as an example, fills in the entire space, even though the have constraints or sizes.

return Scaffold(
      
      body: SafeArea(
        child: NestedScrollView(
          physics: BouncingScrollPhysics(),
          headerSliverBuilder: (context, innerBoxIsScrolled) {
            return <Widget>[];
          },
          body: Container(
            constraints: BoxConstraints(
              maxHeight: 100,
              minWidth: 100,
            ),
            color: Colors.red,
            height: 100,
            width: 100,
            child: Container(
              constraints: BoxConstraints(
                maxHeight: 50,
                minWidth: 50,
              ),
              color: Colors.yellow,
              height: 50,
              width: 50,
              child: Text('a'),
            ),
          ),
        ),
      ),
    );

Solution

You can add a Column over the entire page to control the size of each Container

You can try this:

 return Scaffold(

  body: SafeArea(
    child: NestedScrollView(
      physics: BouncingScrollPhysics(),
      headerSliverBuilder: (context, innerBoxIsScrolled) {
        return <Widget>[];
      },
      body: Column(
        children: [
          Container(

            color: Colors.red,
            height: 100,
            width: 100,
            child: Container(
              
              margin: EdgeInsets.all(25.0),
              color: Colors.yellow,
              height: 50,
              width: 50,
              child: Text('a'),
            ),
          ),
        ],
      ),
    ),
  ),
);