ImageProcess/Archive/lib/widget/touch_bubble.dart

import 'package:flutter/material.dart';

import 'animated_touch_bubble_part.dart';

class TouchBubble extends StatefulWidget {
  TouchBubble({
    required this.size,
    required this.onDrag,
    required this.onDragFinished,
  });

  final double size;
  final Function onDrag;
  final Function onDragFinished;

  @override
  _TouchBubbleState createState() => _TouchBubbleState();
}

class _TouchBubbleState extends State<TouchBubble> {
  bool dragging = false;

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
        behavior: HitTestBehavior.opaque,
        onPanStart: _startDragging,
        onPanUpdate: _drag,
        onPanCancel: _cancelDragging,
        onPanEnd: (_) => _cancelDragging(),
        child: Container(
            width: widget.size,
            height: widget.size,
            decoration: BoxDecoration(
                color: Colors.transparent,
                borderRadius: BorderRadius.circular(widget.size / 2)),
            child: AnimatedTouchBubblePart(
              dragging: dragging,
              size: widget.size,
            )));
  }

  void _startDragging(DragStartDetails data) {
    setState(() {
      dragging = true;
    });
    widget
        .onDrag(data.localPosition - Offset(widget.size / 2, widget.size / 2));
  }

  void _cancelDragging() {
    setState(() {
      dragging = false;
    });
    widget.onDragFinished();
  }

  void _drag(DragUpdateDetails data) {
    if (!dragging) {
      return;
    }

    widget.onDrag(data.delta);
  }
}