Draggable<T>({
  Key? key,
  required this.child,
  this.feedback,
  this.data,
  this.axis,
  this.childWhenDragging,
  this.feedbackOffset = Offset.zero,
  this.dragAnchor = DragAnchor.child,
  this.affinity,
  this.onDragStarted,
  this.onDragEnd,
  this.onDraggableCanceled,
  this.maxSimultaneousDrags,
  this.canDrag = true,
  this.gestureRecognizer,
  this.dragAnchorStrategy = DefaultDragAnchorStrategy,
})

Draggable<int>(
  data: 42,
  child: Container(
    width: 100,
    height: 100,
    color: Colors.blue,
    child: Center(
      child: Text("Drag me"),
    ),
  ),
  feedback: Container(
    width: 120,
    height: 120,
    color: Colors.blue.withOpacity(0.5),
    child: Center(
      child: Text("Dragging..."),
    ),
  ),
  onDragStarted: () {
    // 拖動(dòng)開(kāi)始時(shí)執(zhí)行的操作
    print("Drag started!");
  },
  onDragEnd: (details) {
    // 拖動(dòng)結(jié)束時(shí)執(zhí)行的操作
    print("Drag ended!");
  },
);

DragTarget<T>(
  {Key? key,
  required this.builder,
  this.onWillAccept,
  this.onAccept,
  this.onLeave,
  this.hitTestBehavior = HitTestBehavior.deferToChild,
  this.feedback,
  this.child,
})

DragTarget<int>(
  builder: (BuildContext context, List<int?> candidateData, List<dynamic> rejectedData) {
    return Container(
      width: 200,
      height: 200,
      color: Colors.grey,
      child: Center(
        child: Text("Drop here"),
      ),
    );
  },
  onWillAccept: (data) {
    // 在拖動(dòng)對(duì)象進(jìn)入 DragTarget 區(qū)域時(shí)調(diào)用
    // 返回 true 表示接受拖動(dòng)對(duì)象
    return true;
  },
  onAccept: (data) {
    // 在拖動(dòng)對(duì)象被釋放到 DragTarget 區(qū)域內(nèi)時(shí)調(diào)用
    // 處理接受的拖動(dòng)數(shù)據(jù)
    print("Accepted data: $data");
  },
  onLeave: (data) {
    // 在拖動(dòng)對(duì)象離開(kāi) DragTarget 區(qū)域時(shí)調(diào)用
  },
)

import 'package:flutter/material.dart';
void main() {
  runApp(MyApp());
}
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Draggable and DragTarget Example'),
        ),
        body: MyDraggableAndDragTarget(),
      ),
    );
  }
}
class MyDraggableAndDragTarget extends StatefulWidget {
  @override
  _MyDraggableAndDragTargetState createState() => _MyDraggableAndDragTargetState();
}
class _MyDraggableAndDragTargetState extends State<MyDraggableAndDragTarget> {
  String data = 'Initial Data';
  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        Draggable<String>(
          data: 'Dragged Data',
          child: Container(
            width: 100,
            height: 100,
            color: Colors.blue,
            child: Center(
              child: Text('Drag Me'),
            ),
          ),
          feedback: Container(
            width: 100,
            height: 100,
            color: Colors.blue.withOpacity(0.5),
            child: Center(
              child: Text('Dragging...'),
            ),
          ),
          childWhenDragging: Container(
            width: 100,
            height: 100,
            color: Colors.blue.withOpacity(0.5),
          ),
        ),
        SizedBox(height: 20),
        DragTarget<String>(
          builder: (BuildContext context, List<String?> candidateData, List<dynamic> rejectedData) {
            return Container(
              width: 150,
              height: 150,
              color: Colors.grey,
              child: Center(
                child: Text('Drop Here'),
              ),
            );
          },
          onWillAccept: (data) {
            // 當(dāng)拖動(dòng)對(duì)象進(jìn)入 DragTarget 區(qū)域時(shí)調(diào)用
            // 返回 true 表示接受拖動(dòng)對(duì)象
            return true;
          },
          onAccept: (data) {
            // 當(dāng)拖動(dòng)對(duì)象被釋放到 DragTarget 區(qū)域內(nèi)時(shí)調(diào)用
            // 處理接受的拖動(dòng)數(shù)據(jù)
            setState(() {
              this.data = data ?? 'No Data';
            });
          },
          onLeave: (data) {
            // 當(dāng)拖動(dòng)對(duì)象離開(kāi) DragTarget 區(qū)域時(shí)調(diào)用
          },
        ),
        SizedBox(height: 20),
        Text('Received Data: $data'),
      ],
    );
  }
}