Flutter: Draggable and DragTarget Annotated

flutter_dragtarget_hover.dart

import 'package:flutter/material.dart';

/// Inspiration for how the DragTarget hovering works goes to:
/// Stack Overflow A: https://stackoverflow.com/a/53981607/638153
/// Stack Overflow Q: https://stackoverflow.com/questions/53979586/flutter-dragtarget-on-hover

final Color darkBlue = Color.fromARGB(255, 18, 32, 45);

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: MyWidget(),
        ),
      ),
    );
  }
}

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    Widget helloText(String showText, Color showColor) => Container(
        child: Text(showText, style: Theme.of(context).textTheme.headline4),
        width: 150,
        height: 150,
        color: showColor);

    return Row(
        mainAxisAlignment: MainAxisAlignment.spaceAround,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          Expanded(
            child:
                Column(mainAxisAlignment: MainAxisAlignment.center, children: [
              Draggable<int>(
                data: 1,
                maxSimultaneousDrags: 1,
                child: helloText("D-1-C", Colors.red),
                feedback: helloText("D-1-F", Colors.pink),
                childWhenDragging: helloText("D-1-CwD", Colors.amber),
              ),
              Draggable(
                data: 2,
                maxSimultaneousDrags: 1,
                child: helloText("D-2-C", Colors.yellow),
                feedback: helloText("D-2-F", Colors.green),
                childWhenDragging: helloText("D-2-CwD", Colors.deepPurple),
              ),
              Draggable(
                data: 3,
                maxSimultaneousDrags: 1,
                child: helloText("D-3-C", Colors.blue),
                feedback: helloText("D-3-F", Colors.orange),
                childWhenDragging: helloText("D-3-CwD", Colors.deepOrange),
              ),
            ]),
          ),
          Container(
            height: 300,
            width: 300,
            color: Colors.white,
            child: DragTarget<int>(
              builder: (context, List<int> data, rejectedData) {
                print("builder: $data");
                if (data.isNotEmpty) {
                  if (data[0] == 1) {
                    return Container(
                      height: 100,
                      width: 100,
                      color: Colors.white,
                      child: helloText("DT-C #1", Colors.green),
                    );
                  }
                  return Container(
                    height: 100,
                    width: 100,
                    color: Colors.white30,
                    child: helloText("DT-C #2 or #3", Colors.lightBlue),
                  );
                }
                return Container(
                  height: 100,
                  width: 100,
                  color: Colors.white54,
                  child: helloText("DT-C", Colors.purple),
                );
              },
              onAccept: (data) {
                print(data);
              },
              onWillAccept: (data) => true,
              onLeave: (data) {},
            ),
          ),
        ]);
  }
}