NativeScript 8.2 :如何使用CLHeading trueHeading获取方向

Question

，我正在尝试使用CLHeading trueHeading在我的本地文本应用程序中获得方向，但是它总是返回为null。locationservice.ts

​

import { Injectable } from "@angular/core";

@Injectable()
export class LocationService {

    private iosLocManager: CLLocationManager;
    private locManagerDelegate: LocationMangerDelegate;
    
    constructor() {
        this.iosLocManager = new CLLocationManager();
        this.locManagerDelegate = new LocationMangerDelegate();
        this.iosLocManager.desiredAccuracy = 3;
        this.iosLocManager.distanceFilter = 0.1;
        this.iosLocManager.delegate = this.locManagerDelegate;
    }


     getDirection(): number {
        return this.locManagerDelegate.currentHeading;
    }

    startUpdatingHeading(): void {
       this.locManagerDelegate.currentHeading = null;
      this.iosLocManager.startUpdatingHeading();
    }

    stopUpdatingHeading(): void {
      this.iosLocManager.stopUpdatingHeading();
    }
}

export class LocationMangerDelegate extends NSObject implements CLLocationManagerDelegate {
    public static ObjCProtocols = [CLLocationManagerDelegate];

    currentHeading: number;

    locationManagerDidUpdateHeading(locationManager: CLLocationManager, heading: CLHeading): void {
     this.currentHeading = heading.trueHeading;
    }
    
}

​

组件

​

constructor(private locationService: LocationService) {    
  this.locationService.startUpdatingHeading();
  }
  
  
  GetDirection(): void {
       let direction = this.locationService.getDirection();
    }

​

如何获得trueHeading的值，或者如何在NativeScript IOS中获得方向？

Package.json

​

{
  "dependencies": {
    "@angular/animations": "~13.2.0",
    "@angular/common": "~13.2.0",
    "@angular/compiler": "~13.2.0",
    "@angular/core": "~13.2.0",
    "@angular/forms": "~13.2.0",
    "@angular/http": "7.2.16",
    "@angular/platform-browser": "~13.2.0",
    "@angular/platform-browser-dynamic": "~13.2.0",
    "@angular/router": "~13.2.0",
    "base-64": "^0.1.0",
    "cross-env": "^5.2.0",
    "lodash": "^4.17.11",
    "@nativescript/angular": "^13.0.0",
    "@nativescript/appversion": "2.0.0",
    "@nativescript/camera": "5.0.10",
    "nativescript-couchbase": "^1.0.18",
    "@nativescript/email": "2.0.5",
    "@nativescript/geolocation": "8.0.2",
    "nativescript-phone": "3.0.3",
    "nativescript-screen-orientation": "^2.0.0",
    "nativescript-theme-core": "~1.0.4",
    "reflect-metadata": "~0.1.13",
    "rxjs": "~7.5.0",
    "rxjs-compat": "^6.4.0",
    "utf8": "^3.0.0",
    "zone.js": "~0.11.5",
    "@nativescript/core": "~8.2.0"
  },
  "devDependencies": {
    "@angular/compiler-cli": "~13.2.0",
    "@nativescript/schematics": "~0.5.0",
    "@ngtools/webpack": "~13.2.0",
    "@nativescript/webpack": "5.0.6",
    "@angular-devkit/build-angular": "~13.2.0",
    "@nativescript/ios": "8.2.1",
    "@nativescript/types": "8.1.1",
    "typescript": "~4.5.5"
  },
  "readme": "NativeScript Application",
  "main": "./src/main.ts"
}

​

Reference.d.ts

​

/// <reference path="./node_modules/@nativescript/types/index.d.ts" /> 

​

Info.plist

​

      <key>UIRequiredDeviceCapabilities</key>
          <array>
            <string>magnetometer</string>
            <string>gps</string>
            <string>location-services</string>
     </array>
     <key>NSLocationWhenInUseUsageDescription</key>
     <string>Description</string>
     <key>NSLocationAlwaysAndWhenInUseUsageDescription</key>
     <string>Description</string>
     <key>NSLocationAlwaysUsageDescription</key>
     <string>Description</string>

​

我怎样才能从CLHeading trueHeading那里得到方向？它总是返回null？我少了什么？

Answer 1

检查文档：

只有在为相应的位置管理器对象启用位置更新时，此属性才包含有效值。由于正北的位置不同于磁北在地球表面的位置，核位置需要设备的当前位置来计算这一属性的值。