109 lines
2.7 KiB
Dart
109 lines
2.7 KiB
Dart
import 'dart:math';
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import 'dart:ui';
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import 'package:flutter/material.dart';
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import '../components/coordinate_pro.dart';
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/// create by 张风捷特烈 on 2020-03-19
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/// contact me by email 1981462002@qq.com
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/// 说明: 纸
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class Paper extends StatelessWidget {
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const Paper({super.key});
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@override
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Widget build(BuildContext context) {
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return Center(
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child: HandleWidget(),
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);
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}
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}
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class HandleWidget extends StatefulWidget {
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final double size;
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final double handleRadius;
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HandleWidget({Key? key, this.size = 160, this.handleRadius = 20.0})
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: super(key: key);
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@override
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_HandleWidgetState createState() => _HandleWidgetState();
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}
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class _HandleWidgetState extends State<HandleWidget> {
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ValueNotifier<Offset> _offset = ValueNotifier(Offset.zero);
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@override
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Widget build(BuildContext context) {
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return GestureDetector(
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onPanEnd: reset,
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onPanUpdate: parser,
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child: CustomPaint(
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size: Size(widget.size, widget.size),
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painter: _HandlePainter(
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color: Colors.green,
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handleR: widget.handleRadius,
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offset: _offset)));
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}
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reset(DragEndDetails details) {
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_offset.value = Offset.zero;
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}
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parser(DragUpdateDetails details) {
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final offset = details.localPosition;
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double dx = 0.0;
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double dy = 0.0;
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dx = offset.dx - widget.size / 2;
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dy = offset.dy - widget.size / 2;
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var rad = atan2(dx, dy);
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if (dx < 0) {
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rad += 2 * pi;
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}
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var bgR = widget.size / 2 - widget.handleRadius;
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var thta = rad - pi / 2; //旋转坐标系90度
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if (sqrt(dx * dx + dy * dy) > bgR) {
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dx = bgR * cos(thta);
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dy = -bgR * sin(thta);
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}
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_offset.value = Offset(dx, dy);
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}
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}
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class _HandlePainter extends CustomPainter {
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final _paint = Paint();
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final ValueNotifier<Offset> offset;
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final Color color;
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var handleR;
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_HandlePainter({this.handleR,required this.offset, this.color = Colors.blue})
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: super(repaint: offset) ;
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@override
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void paint(Canvas canvas, Size size) {
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canvas.clipRect(Offset.zero & size);
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final bgR = size.width / 2 - handleR;
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canvas.translate(size.width / 2, size.height / 2);
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_paint.style = PaintingStyle.fill;
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_paint.color = color.withAlpha(100);
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canvas.drawCircle(Offset(0, 0), bgR, _paint);
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_paint.color = color.withAlpha(150);
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canvas.drawCircle(
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Offset(offset.value.dx, offset.value.dy), handleR, _paint);
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_paint.color = color;
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_paint.style = PaintingStyle.stroke;
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canvas.drawLine(Offset.zero, offset.value, _paint);
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}
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@override
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bool shouldRepaint(_HandlePainter oldDelegate) =>
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oldDelegate.offset != offset ||
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oldDelegate.color != color ||
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oldDelegate.handleR != handleR;
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} |