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lib/cases/paper/paper.dart

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+import 'dart:math';
+import 'dart:ui';
+
+import 'package:flutter/material.dart';
+import 'color_selector.dart';
+import 'conform_dialog.dart';
+
+import 'model.dart';
+import 'paper_app_bar.dart';
+import 'stork_width_selector.dart';
+
+class Paper extends StatefulWidget {
+  const Paper({Key? key}) : super(key: key);
+
+  @override
+  State<Paper> createState() => _PaperState();
+}
+
+class _PaperState extends State<Paper>  with AutomaticKeepAliveClientMixin {
+
+  @override
+  bool get wantKeepAlive => true;
+
+
+  List<Line> _lines = []; // 线列表
+
+  int _activeColorIndex = 0; // 颜色激活索引
+  int _activeStorkWidthIndex = 0; // 线宽激活索引
+
+  // 支持的颜色
+  final List<Color> supportColors = [
+    Colors.black,
+    Colors.red,
+    Colors.orange,
+    Colors.yellow,
+    Colors.green,
+    Colors.blue,
+    Colors.indigo,
+    Colors.purple,
+    Colors.pink,
+    Colors.grey,
+    Colors.redAccent,
+    Colors.orangeAccent,
+    Colors.yellowAccent,
+    Colors.greenAccent,
+    Colors.blueAccent,
+    Colors.indigoAccent,
+    Colors.purpleAccent,
+    Colors.pinkAccent,
+  ];
+
+  // 支持的线粗
+  final List<double> supportStorkWidths = [1, 2, 4, 6, 8, 10];
+
+  List<Line> _historyLines = [];
+
+  void _back() {
+    Line line = _lines.removeLast();
+    _historyLines.add(line);
+    setState(() {});
+  }
+
+  void _revocation() {
+    Line line = _historyLines.removeLast();
+    _lines.add(line);
+    setState(() {});
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: PaperAppBar(
+        onClear: _showClearDialog,
+        onBack: _lines.isEmpty ? null : _back,
+        onRevocation: _historyLines.isEmpty ? null : _revocation,
+      ),
+      body: Stack(
+        children: [
+          GestureDetector(
+            onPanStart: _onPanStart,
+            onPanUpdate: _onPanUpdate,
+            child: CustomPaint(
+              painter: PaperPainter(lines: _lines),
+              child: ConstrainedBox(constraints: const BoxConstraints.expand()),
+            ),
+          ),
+          Positioned(
+            bottom: 0,
+            width: MediaQuery.of(context).size.width,
+            child: Row(
+              children: [
+                Expanded(
+                  child: ColorSelector(
+                    supportColors: supportColors,
+                    activeIndex: _activeColorIndex,
+                    onSelect: _onSelectColor,
+                  ),
+                ),
+                StorkWidthSelector(
+                  supportStorkWidths: supportStorkWidths,
+                  color: supportColors[_activeColorIndex],
+                  activeIndex: _activeStorkWidthIndex,
+                  onSelect: _onSelectStorkWidth,
+                ),
+              ],
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+
+  void _showClearDialog() {
+    String msg = "您的当前操作会清空绘制内容，是否确定删除!";
+    showDialog(
+        context: context,
+        builder: (ctx) => ConformDialog(
+              title: '清空提示',
+              conformText: '确定',
+              msg: msg,
+              onConform: _clear,
+            ));
+  }
+
+  void _clear() {
+    _lines.clear();
+    Navigator.of(context).pop();
+    setState(() {});
+  }
+
+  void _onPanStart(DragStartDetails details) {
+    _lines.add(Line(
+      points: [details.localPosition],
+      strokeWidth: supportStorkWidths[_activeStorkWidthIndex],
+      color: supportColors[_activeColorIndex],
+    ));
+  }
+
+  void _onPanUpdate(DragUpdateDetails details) {
+    Offset point = details.localPosition;
+    double distance = (_lines.last.points.last - point).distance;
+    if (distance > 5) {
+      _lines.last.points.add(details.localPosition);
+      setState(() {});
+    }
+  }
+
+  void _onSelectStorkWidth(int index) {
+    if (index != _activeStorkWidthIndex) {
+      setState(() {
+        _activeStorkWidthIndex = index;
+      });
+    }
+  }
+
+  void _onSelectColor(int index) {
+    if (index != _activeColorIndex) {
+      setState(() {
+        _activeColorIndex = index;
+      });
+    }
+  }
+
+}
+
+class PaperPainter extends CustomPainter {
+  PaperPainter({
+    required this.lines,
+  }) {
+    _paint = Paint()
+      ..style = PaintingStyle.stroke
+      ..strokeCap = StrokeCap.round;
+  }
+
+  late Paint _paint;
+  final List<Line> lines;
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    for (int i = 0; i < lines.length; i++) {
+      drawLine(canvas, lines[i]);
+    }
+  }
+
+  ///根据点位绘制线
+  void drawLine(Canvas canvas, Line line) {
+    _paint.color = line.color;
+    _paint.strokeWidth = line.strokeWidth;
+    canvas.drawPoints(PointMode.polygon, line.points, _paint);
+  }
+
+  @override
+  bool shouldRepaint(CustomPainter oldDelegate) => true;
+}