DecoratedBox | DecoratedBoxTransistion in Flutter

A widget that paints a Decoration either before or after its child paints.

Container insets its child by the widths of the borders; DecoratedBox does not.

DecoratedBox is commonly used with BoxDecoration.
you can watch the video at

DecoratedBox({Key? key, required Decoration decoration, DecorationPosition position, Widget? child})

DecoratedBox(
        decoration: BoxDecoration(
          gradient: RadialGradient(
            center: Alignment(-0.5, -0.6),
            radius: 0.15,
            colors: <Color>[
              Color(0xFFEEEEEE),
              Color(0xFF111133),
            ],
            stops: <double>[0.9, 1.0],
          ),
        ),
        position: DecorationPosition.background,
        child: FlutterLogo(size: 400));

position determines whether the decoration should be at foreground or background to the child.
The above decoration created a full moon with dark night background of FlutterLogo()

DecoratedBoxTransistion

Declare it in a statefulwidget and declare the DecorationTween.

final DecorationTween decorationTween = DecorationTween(
      begin: BoxDecoration(
        gradient: RadialGradient(
          center: Alignment(-0.5, -0.6),
          radius: 0.15,
          colors: <Color>[
            Color(0xFFEEEEEE),
            Color(0xFF111133),
          ],
          stops: <double>[0.9, 1.0],
        ),
      ),
      end: BoxDecoration(
        gradient: RadialGradient(
          center: Alignment(-0.5, -0.6),
          radius: 0.15,
          colors: <Color>[
            Colors.orange,
            Colors.cyan,
          ],
          stops: <double>[0.9, 1.0],
        ),
      ));

Declare and intialize AnimationController

  AnimationController _controller;
  @override
  void initState() {
    super.initState();
    _controller =
        AnimationController(vsync: this, duration: Duration(seconds: 5))
          ..repeat(reverse: true);
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

finally return DecorationBoxTransistion

child: DecoratedBoxTransition(
          position: DecorationPosition.background,
          decoration: decorationTween.animate(_controller),
          child: Container(
              width: 800,
              height: 1000,
              padding: EdgeInsets.all(10),
              child: Container()),),