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通过 Amazon Location Service，把 ES 用于 iOS

Tangram ES 是一个 C++ 库，用于使用 OpenGL ES 根据矢量数据渲染 2D 和 3D 地图。它是 Tangram 的原生对应部分。

使用来自的地图时，专为使用 Tilezen 架构而设计的七巧板风格在很大程度上与 Amazon Location 兼容。HERE其中包括：

本指南介绍如何使用名为 Cinnabar 的 Tangram 风格将 iOS 版 Tangram ES 与 Amazon Location 集成。此示例作为 Amazon Location Service 示例存储库的一部分提供GitHub。

虽然其他 Tangram 风格最好搭配编码地形信息的栅格图块，但 Amazon Location 尚不支持此功能。

构建应用程序：初始化

初始化应用程序：

构建应用程序：添加依赖项

要添加依赖关系，您可以使用依赖关系管理器，例如 CocoaPods：

构建应用程序：配置

将以下键和值添加到 Info.plist 以配置应用程序并禁用遥测：

构建应用程序： ContentView 布局

要渲染地图，请编辑 ContentView.swift：

这还会设置地图的初始中心点。

import SwiftUI
import TangramMap
 
struct ContentView: View {
    var body: some View {
        MapView()
            .cameraPosition(TGCameraPosition(
                                center: CLLocationCoordinate2DMake(49.2819, -123.1187),
                                zoom: 10,
                                bearing: 0,
                                pitch: 0))
            .edgesIgnoringSafeArea(.all)
            .overlay(
                Text("© 2020 HERE")
                    .disabled(true)
                    .font(.system(size: 12, weight: .light, design: .default))
                    .foregroundColor(.black)
                    .background(Color.init(Color.RGBColorSpace.sRGB, white: 0.5, opacity: 0.5))
                    .cornerRadius(1),
                alignment: .bottomTrailing)
    }
}
 
struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

构建应用程序：请求转换

创建一个名为的新 Swift 文件，AWSSignatureV4URLHandler.swift其中包含以下类定义，用于拦截 AWS 请求并使用签名版本 4 对其进行签名。这将在七巧板MapView中注册为URL处理者。

import AWSCore
import TangramMap
 
class AWSSignatureV4URLHandler: TGDefaultURLHandler {
    private let region: AWSRegionType
    private let identityPoolId: String
    private let credentialsProvider: AWSCredentialsProvider
 
    init(region: AWSRegionType, identityPoolId: String) {
        self.region = region
        self.identityPoolId = identityPoolId
        self.credentialsProvider = AWSCognitoCredentialsProvider(regionType: region, identityPoolId: identityPoolId)
        super.init()
    }
 
    override func downloadRequestAsync(_ url: URL, completionHandler: @escaping TGDownloadCompletionHandler) -> UInt {
        if url.host?.contains("amazonaws.com") != true {
            // not an AWS URL
            return super.downloadRequestAsync(url, completionHandler: completionHandler)
        }
 
        // URL-encode spaces, etc.
        let keyPath = String(url.path.dropFirst())
        guard let keyPathSafe = keyPath.addingPercentEncoding(withAllowedCharacters: .urlPathAllowed) else {
            print("Invalid characters in path '\(keyPath)'; unsafe to sign")
            return super.downloadRequestAsync(url, completionHandler: completionHandler)
        }
 
        // sign the URL
        let endpoint = AWSEndpoint(region: region, serviceName: "geo", url: url)
        let requestHeaders: [String: String] = ["host": endpoint!.hostName]
        let task = AWSSignatureV4Signer
            .generateQueryStringForSignatureV4(
                withCredentialProvider: credentialsProvider,
                httpMethod: .GET,
                expireDuration: 60,
                endpoint: endpoint!,
                keyPath: keyPathSafe,
                requestHeaders: requestHeaders,
                requestParameters: .none,
                signBody: true)
        task.waitUntilFinished()
 
        if let error = task.error as NSError? {
            print("Error occurred: \(error)")
        }
 
        if let result = task.result {
            // have Tangram fetch the signed URL
            return super.downloadRequestAsync(result as URL, completionHandler: completionHandler)
        }
 
        // fall back to an unsigned URL
        return super.downloadRequestAsync(url, completionHandler: completionHandler)
    }
}

构建应用程序：地图视图

地图视图负责初始化实例 AWSSignatureV4Delegate 和配置底层 MGLMapView，底层视图获取资源并渲染地图。它还处理将属性字符串从样式描述符的来源传播回 ContentView。

创建一个名为 MapView.swift 的新 Swift 文件，其中包含以下 struct 定义：

import AWSCore
import TangramMap
import SwiftUI
 
struct MapView: UIViewRepresentable {
    private let mapView: TGMapView
 
    init() {
        let regionName = Bundle.main.object(forInfoDictionaryKey: "AWSRegion") as! String
        let identityPoolId = Bundle.main.object(forInfoDictionaryKey: "IdentityPoolId") as! String
        let mapName = Bundle.main.object(forInfoDictionaryKey: "MapName") as! String
        let sceneURL = URL(string: Bundle.main.object(forInfoDictionaryKey: "SceneURL") as! String)!
 
        let region = (regionName as NSString).aws_regionTypeValue()
 
        // rewrite tile URLs to point at AWS resources
        let sceneUpdates = [
            TGSceneUpdate(path: "sources.mapzen.url",
                          value: "https://maps.geo.\(regionName).amazonaws.com/maps/v0/maps/\(mapName)/tiles/{z}/{x}/{y}")]
 
        // instantiate a TGURLHandler that will sign AWS requests
        let urlHandler = AWSSignatureV4URLHandler(region: region, identityPoolId: identityPoolId)
 
        // instantiate the map view and attach the URL handler
        mapView = TGMapView(frame: .zero, urlHandler: urlHandler)
 
        // load the map style and apply scene updates (properties modified at runtime)
        mapView.loadScene(from: sceneURL, with: sceneUpdates)
    }
 
    func cameraPosition(_ cameraPosition: TGCameraPosition) -> MapView {
        mapView.cameraPosition = cameraPosition
 
        return self
    }
 
    // MARK: - UIViewRepresentable protocol
 
    func makeUIView(context: Context) -> TGMapView {
        return mapView
    }
 
    func updateUIView(_ uiView: TGMapView, context: Context) {
    }
}

运行此应用程序会以您选择的样式显示全屏地图。此示例作为 Amazon Location Service 示例存储库的一部分提供GitHub。