tanlongsheng
2 years ago
3 changed files with 186 additions and 4 deletions
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import 'dart:convert'; |
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import 'dart:math'; |
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import 'dart:math' as math; |
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import 'package:flutter/material.dart'; |
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import 'package:http/http.dart' as http; |
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class ChatNavigationCard extends StatefulWidget { |
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final Map? data; |
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final bool isDarkMode; |
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const ChatNavigationCard(this.data, this.isDarkMode, {super.key}); |
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@override |
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State<ChatNavigationCard> createState() => _ChatNavigationCardState(); |
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} |
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class _ChatNavigationCardState extends State<ChatNavigationCard> { |
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final String apiKey = '8bde023b7e5e00f321ea17929f10fbae'; |
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LatLng startPoint = LatLng(116.397428, 39.90923); // 起点坐标 |
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LatLng endPoint = LatLng(116.397026, 39.903303); // 终点坐标 |
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@override |
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void initState() { |
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super.initState(); |
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_getMapUrl(); |
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} |
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Future<String> _getMapUrl() async { |
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// 1. 获取路径数据 |
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final route = await _fetchRouteData(); |
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// 2. 解析并简化路径 |
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List<LatLng> simplified = _simplifyPath(route, epsilon: 0.0001); |
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// 3. 计算地图参数 |
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final zoom = _calculateAutoZoom(simplified); |
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// 4. 生成静态地图URL |
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return _buildStaticMapUrl(simplified, zoom); |
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} |
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Future<List<LatLng>> _fetchRouteData() async { |
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final url = 'https://restapi.amap.com/v3/direction/driving?' |
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'origin=${startPoint.lng},${startPoint.lat}&' |
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'destination=${endPoint.lng},${endPoint.lat}&' |
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'key=$apiKey'; |
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final response = await http.get(Uri.parse(url)); |
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if (response.statusCode == 200) { |
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final data = json.decode(response.body); |
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return _parsePolyline(data['route']['paths'][0]['steps']); |
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} |
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throw Exception('Failed to load route'); |
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} |
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List<LatLng> _parsePolyline(List<dynamic> steps) { |
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final List<LatLng> path = []; |
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for (final step in steps) { |
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final points = (step['polyline'] as String).split(';'); |
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for (final point in points) { |
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final coords = point.split(',').map(double.parse).toList(); |
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path.add(LatLng(coords[0], coords[1])); |
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} |
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} |
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return path; |
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} |
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List<LatLng> _simplifyPath(List<LatLng> points, {double epsilon = 0.0001}) { |
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return douglasPeucker(points, epsilon); |
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} |
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int _calculateAutoZoom(List<LatLng> points, |
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{int mapWidth = 1024, int mapHeight = 512}) { |
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if (points.isEmpty) return 15; // 默认缩放级别 |
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// 1. 计算坐标范围 |
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double minLng = double.infinity; |
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double maxLng = -double.infinity; |
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double minLat = double.infinity; |
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double maxLat = -double.infinity; |
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for (final p in points) { |
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final lng = p.lng; |
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final lat = p.lat; |
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minLng = math.min(minLng, lng); |
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maxLng = math.max(maxLng, lng); |
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minLat = math.min(minLat, lat); |
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maxLat = math.max(maxLat, lat); |
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} |
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// 3. 计算缩放级别（基于Leaflet算法改进） |
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const worldWidth = 256; // 高德瓦片尺寸 |
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const worldHeight = 256; |
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const zoomMax = 18; // 高德最大缩放级别 |
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double latRad(double lat) { |
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final sin = math.sin(lat * math.pi / 180); |
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return math.log((1 + sin) / (1 - sin)) / 2; |
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} |
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final latFraction = (latRad(maxLat) - latRad(minLat)) / math.pi; |
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final lngDiff = maxLng - minLng; |
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final lngFraction = ((lngDiff < 0) ? (lngDiff + 360) : lngDiff) / 360; |
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final latZoom = |
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math.log((mapHeight / worldHeight) / latFraction) / math.ln2; |
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final lngZoom = math.log((mapWidth / worldWidth) / lngFraction) / math.ln2; |
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return math.min(math.min(latZoom, lngZoom).floor(), zoomMax); |
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} |
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String _buildStaticMapUrl(List<LatLng> path, int zoom) { |
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final pathParam = path.map((p) => '${p.lng},${p.lat}').join(';'); |
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return 'https://restapi.amap.com/v3/staticmap?' |
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'zoom=$zoom&' |
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'size=1024*512&' |
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'paths=10,0x0000ff,1,,:$pathParam&' |
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'markers=mid,,A:${startPoint.lng},${startPoint.lat}|' |
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'mid,,B:${endPoint.lng},${endPoint.lat}&' |
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'key=$apiKey'; |
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} |
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List<LatLng> douglasPeucker(List<LatLng> points, double epsilon) { |
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if (points.length < 3) return points; |
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double maxDistance = 0; |
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int index = 0; |
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for (int i = 1; i < points.length - 1; i++) { |
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double d = _perpendicularDistance(points[i], points.first, points.last); |
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if (d > maxDistance) { |
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index = i; |
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maxDistance = d; |
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} |
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} |
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if (maxDistance > epsilon) { |
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return [ |
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...douglasPeucker(points.sublist(0, index + 1), epsilon), |
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...douglasPeucker(points.sublist(index), epsilon).skip(1) |
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]; |
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} |
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return [points.first, points.last]; |
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} |
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double _perpendicularDistance(LatLng point, LatLng start, LatLng end) { |
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final area = (end.lng - start.lng) * (point.lat - start.lat) - |
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(end.lat - start.lat) * (point.lng - start.lng); |
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final length = |
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sqrt(pow(end.lng - start.lng, 2) + pow(end.lat - start.lat, 2)); |
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return area.abs() / length; |
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} |
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@override |
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Widget build(BuildContext context) { |
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return Column( |
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children: [ |
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FutureBuilder( |
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future: _getMapUrl(), |
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builder: (BuildContext context, AsyncSnapshot snapshot) { |
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if (snapshot.hasData) { |
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return Image.network(snapshot.data); |
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} |
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return const CircularProgressIndicator(); |
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}, |
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), |
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], |
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); |
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} |
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} |
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class LatLng { |
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final double lat; |
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final double lng; |
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LatLng(this.lng, this.lat); // 高德使用经度在前纬度在后的格式 |
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} |
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