Flutter - Overlay card widget on a container

Question

In flutter, is it possible to place a part of a card on another container? In CSS, we would set margin-top to a negative value or use translate property. In flutter as we ca

Answer 1

To do this,You Implement Positioned of the card using Stack widget in Flutter.

Stack class is useful if you want to overlap several children in a simple way,

Positioned widget that controls where a child of a Stack is positioned.

Note: Stack paints its children in order with the first child being at the bottom.

Answer 2

Here is running example with overlay:

class _MyHomePageState extends State<MyHomePage> {
     double _width = 0.0;
     double _height = 0.0;

     @override
     Widget build(BuildContext context) {
      _width = MediaQuery.of(context).size.width;
      _height = MediaQuery.of(context).size.height;
      return Scaffold(
       backgroundColor: Colors.white,
       body: Stack(
        children: <Widget>[
          // The containers in the background and scrollable
         getScrollableBody(),

         // This container will work as Overlay
         getOverlayWidget()
        ],
      ),
   );
 }

 Widget getOverlayWidget() {
   return new Container(
     alignment: Alignment.bottomCenter,
     child: new Container(
      height: 100.0,
      width: _width,
      color: Colors.cyan.withOpacity(0.4),
     ),
   );
 }
 Widget getScrollableBody() {
  return SingleChildScrollView(
    child: new Column(
      children: <Widget>[
        new Container(
         height: _height * .65,
         color: Colors.yellow,
       ),
       new Container(
         height: _height * .65,
         color: Colors.brown,
       ),
       new Container(
        margin: EdgeInsets.only(bottom: 100.0),
        height: _height * .65,
        color: Colors.orange,
       ),
     ],
   ),
  );
 }
}

Here is Result of code: Scrollable Body under customised Bottom Bar

Answer 3

Yes, you can acheive it with a Stack widget. You can stack a card over the background and provide a top or bottom padding.

A simple example would look like:

class StackDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Stack(
      children: <Widget>[
        // The containers in the background
        new Column(
          children: <Widget>[
            new Container(
              height: MediaQuery.of(context).size.height * .65,
              color: Colors.blue,
            ),
            new Container(
              height: MediaQuery.of(context).size.height * .35,
              color: Colors.white,
            )
          ],
        ),
        // The card widget with top padding, 
        // incase if you wanted bottom padding to work, 
        // set the `alignment` of container to Alignment.bottomCenter
        new Container(
          alignment: Alignment.topCenter,
          padding: new EdgeInsets.only(
              top: MediaQuery.of(context).size.height * .58,
              right: 20.0,
              left: 20.0),
          child: new Container(
            height: 200.0,
            width: MediaQuery.of(context).size.width,
            child: new Card(
              color: Colors.white,
              elevation: 4.0,
            ),
          ),
        )
      ],
    );
  }
}

The output of the above code would look something like:

Hope this helps!