How to make button width match parent?

I want to know that how can I set a width to match parent layout width

new Container(
  width: 200.0,
  padding: const EdgeInsets.only(top: 16.0),
  child: new RaisedButton(
    child: new Text(
      "Submit",
      style: new TextStyle(
        color: Colors.white,
      )
    ),
    colorBrightness: Brightness.dark,
    onPressed: () {
      _loginAttempt(context);
    },
    color: Colors.blue,
  ),
),

I know about little bit on Expanded widget but Expanded expands view to both direction, i dont know how to do it.

Solution 1:

Update:

With Flutter 2.0 RaisedButton is deprecated and replaced by ElevatedButton. you can use minimumSize like this:

ElevatedButton(
        style: ElevatedButton.styleFrom(
          minimumSize: Size.fromHeight(40), // fromHeight use double.infinity as width and 40 is the height
        ),
        onPressed: () {},
        child: Text('Text Of Button'),
      )

Old answer for Flutter less than 2.0:

The correct solution would be to use the SizedBox.expand widget, which enforces its child to match its parent's size.

SizedBox.expand(
  child: RaisedButton(...),
)

There are many alternatives, which allows for more or less customization:

SizedBox(
  width: double.infinity,
  // height: double.infinity,
  child: RaisedButton(...),
)

or using a ConstrainedBox

ConstrainedBox(
    constraints: const BoxConstraints(minWidth: double.infinity),
    child: RaisedButton(...),
)

Solution 2:

Container(
  width: double.infinity,
  child: RaisedButton(...),
),