Flutter - How create Container with width match parent?

Question

I use this simple widget in my Flutter app:

  FlatButton(
   child: Column(
          children: <Widget>[
            Image.asset(assets, height: 40, width: 40),
            Text('Title'),
            //my color line
            Container(
              height: 5,
              width: ?,
              color: Colors.blue[800],
            )
          ],
        )
  )

I need color line (in buttom), with width match parent. but I don’t know how to do it.

Answer 1

Container(
    height: 5,
    width: double.infinity,
    color: Colors.blue[800],
)

Answer 2

Use IntrinsicWidth

 FlatButton(
   child: IntrinsicWidth(
   child: Column(
          mainAxisSize: MainAxisSize.min,
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: <Widget>[
            Image.asset(assets, height: 40, width: 40),
            Text('Title'),
            //my color line
            Container(
              height: 5,
              width: ?,
              color: Colors.blue[800],
            )
          ],
        ))
  )

Some cheatsheet

Answer 3

Two ways of doing this

ConstrainedBox:

It Creates a widget that imposes additional constraints on its child, which internally uses SingleChildRenderObjectWidget to add constraints over the child widget.

ConstrainedBox(
        constraints:
            const BoxConstraints(minWidth: double.infinity, maxHeight: 10),
        child: Container(
          color: Colors.blue,
        ),
      ),

SizedBox:

SizedBox simply creates a box with a given width/height and doesn't allow the child to go beyond given dimensions. It also used SingleChildRenderObjectWidget to decide the child render area

SizedBox(
        width: double.infinity,
        height: 5,
        // height: double.infinity,
        child: Container(
          color: Colors.blue,
        ),
      ),