how to exactly take x and y value of screen in flutter code example

Example 1: get position of a widget in screen flutter

@override  void initState() {    WidgetsBinding.instance.addPostFrameCallback(_afterLayout);    super.initState();  } _afterLayout(_) {    _getSizes();    _getPositions();  }

Example 2: get position of a widget in screen flutter

//creating Key for red panelGlobalKey _keyRed = GlobalKey();...//set key    Flexible(             flex: 2,             child: Container(               key: _keyRed,               color: Colors.red,             ),     ),