How can I put a widget above another widget in Flutter?

@overrideWidget build(BuildContext context) {// TODO: implement buildreturn new Container(  width: 150.0,  height: 150.0,  child: new Stack(children: <Widget>[    new Container(      alignment: Alignment.center,      color: Colors.redAccent,      child: Text('Hello'),    ),    new Align(alignment: Alignment.bottomRight,      child: FloatingActionButton(        child: new Icon(Icons.add),          onPressed: (){}),    )  ],  ),);}

You can use the Stack widget.

Stack(  children: [    /*your_widget_1*/,    /*your_widget_2*/,  ],);

             Stack(                alignment: Alignment.topRight,                children: <Widget>[                  Padding(                    padding: const EdgeInsets.all(8.0),                    child: ClipRRect(                      child: Image.network(                        image,                        height: 150,                        width: 100,                        fit: BoxFit.fitHeight,                      ),                      borderRadius: new BorderRadius.circular(8.0),                    ),                  ),                  new Align(alignment: Alignment.topRight,                    child:ClipRRect(                      borderRadius: BorderRadius.only(                          bottomRight: Radius.circular(30),                          bottomLeft: Radius.circular(30),                          topRight: Radius.circular(30)),                      child: RaisedButton(                        elevation: 1,                        color: Color(0xFF69C86C),                        child: Text(                          "Name",                          style: TextStyle(color: Colors.white),                        ),                        onPressed: () {},                      ),                    ),                  )                ],              ),