如何在颤动的大小框中添加两个参数？

Question

I wanted to change the size of the raised Button.. So i created a sized box and added width and height as I wanted and wrapped the raised button inside the sized box... After I did that the button sticks to the left corner only.. So I used the align widget to keep it in center but since I made to child under the sized box it became an error.. So how to rectify this?!

SizedBox(
               width: 100.0,
               height: 50.0,
                 child: Align(
                 alignment: Alignment.center,
               ),
               child: RaisedButton(
               child: Center(child: Text("Sign Up", style: TextStyle(color: Colors.white.withOpacity(.7)),)),
                  color: Colors.blue[800],
              onPressed: () {
               Navigator.push(
                context, 
               MaterialPageRoute(builder: (context)=> UserPage()));
               }
              ),
             )

Answer 1

try like this,

     SizedBox(
          height: 50.0,              
          child: Row(
            mainAxisSize: MainAxisSize.min,
            children: <Widget>[
              RaisedButton(
                  child: Center(
                      child: Text(
                    "Sign Up",
                    style: TextStyle(color: Colors.white.withOpacity(.7)),
                  )),
                  color: Colors.blue[800],
                  onPressed: () {
                    Navigator.push(context,
                        MaterialPageRoute(builder: (context) => UserPage()));
                  }),
            ],
          ),
        )

Answer 2

Simply wrap with center widget

Center(
  child: SizedBox(
             width: 100.0,
             height: 50.0,                  
             child: RaisedButton(
             child: Center(child: Text("Sign Up", style: TextStyle(color: Colors.white.withOpacity(.7)),)),
                color: Colors.blue[800],
            onPressed: () {

             }
            )
    ),
)