Flutter调用Routes API而非Directions API获取高精度折线的请求示例

准备工作 #

• 确保已在Google Cloud控制台启用Routes API，并获取有效的API密钥
• 在pubspec.yaml中添加依赖（http用于发送请求，flutter_polyline_points用于解码折线）：

dependencies:
  flutter:
    sdk: flutter
  http: ^1.1.0
  flutter_polyline_points: ^1.0.0

完整实现代码 #

1. 导入依赖 #

import 'dart:convert';
import 'package:http/http.dart' as http;
import 'package:flutter_polyline_points/flutter_polyline_points.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';

2. 核心请求函数 #

// 替换为你的Google Routes API密钥
const String apiKey = 'YOUR_GOOGLE_ROUTES_API_KEY';

Future<List<LatLng>?> fetchHighPrecisionRoute() async {
  final url = Uri.parse('https://routes.googleapis.com/directions/v2:computeRoutes');
  
  // 构建请求体，指定高精度折线参数
  final requestBody = jsonEncode({
    "origin": {
      "location": {
        "latLng": {
          "latitude": 37.7749, // 起点纬度
          "longitude": -122.4194 // 起点经度
        }
      }
    },
    "destination": {
      "location": {
        "latLng": {
          "latitude": 37.3352, // 终点纬度
          "longitude": -121.8811 // 终点经度
        }
      }
    },
    "travelMode": "DRIVING",
    "polylineQuality": "HIGH_QUALITY", // 关键：开启高精度折线
    "routeModifiers": {
      "avoidTolls": false,
      "avoidHighways": false
    }
  });

  try {
    final response = await http.post(
      url,
      headers: {
        'Content-Type': 'application/json',
        'X-Goog-Api-Key': apiKey,
        // 指定返回字段，减少响应体积并符合API要求
        'X-Goog-FieldMask': 'routes.polyline.encodedPolyline'
      },
      body: requestBody,
    );

    if (response.statusCode == 200) {
      final data = jsonDecode(response.body);
      final encodedPolyline = data['routes'][0]['polyline']['encodedPolyline'];
      
      // 解码高精度折线为坐标点列表
      final polylinePoints = PolylinePoints();
      final result = polylinePoints.decodePolyline(encodedPolyline);
      return result.map((point) => LatLng(point.latitude, point.longitude)).toList();
    } else {
      print('请求失败：${response.statusCode} - ${response.body}');
      return null;
    }
  } catch (e) {
    print('请求异常：$e');
    return null;
  }
}

关键参数说明 #

• polylineQuality: "HIGH_QUALITY"：这是获取高精度折线的核心配置，Routes API会返回比Directions API更精细的路径点
• X-Goog-FieldMask：Routes API强制要求指定返回字段，这里仅请求折线相关内容，提升请求效率
• origin和destination可根据业务需求替换为动态坐标

使用示例 #

在Widget的初始化逻辑或交互事件中调用：

@override
void initState() {
  super.initState();
  fetchHighPrecisionRoute().then((routePoints) {
    if (routePoints != null) {
      // 处理路径坐标，比如在Google Maps上绘制折线
      print('获取到${routePoints.length}个高精度路径点');
    }
  });
}

内容的提问来源于stack exchange，提问作者Fayis Fazio