Flutter RawMaterialButton 常量相对大小

我怎么做才能让原material 按钮的大小与我的设备相对.

我想让主页中的按钮具有恒定的宽度，而不管其中的文本有多大，并且该宽度应该与屏幕大小相关.

Container(
                margin: EdgeInsets.all(10),
                child: FittedBox(
                  child: RawMaterialButton(
                    width: 150px,
                    fillColor: const Color(0xFF411F97),
                    padding: const EdgeInsets.fromLTRB(50, 10, 50, 10),
                    shape: const RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(20),)),
                    child: const Text("San Francisco Area", style: TextStyle(fontSize: 50, color: Colors.white,), textAlign: TextAlign.center,),
                    //Sends user to weather list view
                    onPressed: () {
                      Navigator.push(
                        context,
                        MaterialPageRoute(builder: (context) => WeatherList(title: "San Francisco Metro Area", cityNames: sfaNames,)),
                      );
                    },
                  ),
                ),
                //Box shadow is essentially made here for the botton
                decoration: BoxDecoration(
                  color: Colors.teal,
                  borderRadius: BorderRadius.circular(20),
                  boxShadow: const [
                    BoxShadow(
                      color: Colors.black26,
                      offset: Offset(10, 10), // Shadow position
                    ),
                  ],
                )
            ),