Question

我做了一些服务，一些观察者需要订阅才能获得一些数据。问题是服务不在构造函数中，因此永远不会创建实例！如何强制或有其他方法来做到这一点？我正在使用IONIC2框架的Event。我可以在构造函数中添加Class，即使我不使用它，但也许有一个最好的解决方案。提前谢谢。

import {Injectable } from "@angular/core";
import {log, PRIORITY_INFO, PRIORITY_ERROR} from "./log";
import { BackgroundGeolocation } from 'ionic-native';
import Timer = NodeJS.Timer;
import {Platform, Events} from "ionic-angular";

@Injectable()
export class BackgroundGeolocationService {

    trackerInterval: Timer;
    locations: any;

    constructor(private platform: Platform, public trace: log, private events: Events) {
        this.trace.info('create BackgroundGeolocationService');

        if (this.platform.is('android')) {
            this.platform.ready().then(() => {

                this.trace.info(`platform android ready` );

                // BackgroundGeolocation is highly configurable. See platform specific configuration options
                let config = {
                    interval: 1000,
                    locationTimeout: 100,
                    desiredAccuracy: 10,
                    stationaryRadius: 20,
                    distanceFilter: 30,
                    debug: true, //  enable this hear sounds for background-geolocation life-cycle.
                    stopOnTerminate: false // enable this to clear background location settings when the app terminates
                };

                BackgroundGeolocation.configure((location) => {
                    this.trace.info(`configure  ${location.latitude},${location.longitude}`);

                    this.setCurrentLocation(location);
                    this.startTrackingInterval();

                    // IMPORTANT:  You must execute the finish method here to inform the native plugin that you're finished,
                    // and the background-task may be completed.  You must do this regardless if your HTTP request is successful or not.
                    // IF YOU DON'T, ios will CRASH YOUR APP for spending too much time in the background.
                    //BackgroundGeolocation.finish(); // FOR IOS ONLY

                }, (error) => {
                    this.trace.error(error);
                }, config);

                // Turn ON the background-geolocation system.  The user will be tracked whenever they suspend the app.
                BackgroundGeolocation.start();

            }).catch(err => {
                this.trace.error(err);
            });

        }
    }

    startTrackingInterval(): void {
        this.trackerInterval = setInterval(() => { this.refreshLocations(); }, 2000);
    }

    refreshLocations(): void {
        BackgroundGeolocation.getLocations().then(locations => {
            this.locations = locations;
            if (locations.length != 0) {
                this.setCurrentLocation(locations[locations.length-1]);
            }
        }).catch(error => {
            this.trace.error(`BackgroundGeolocationService error ${error}`);
        });
    }

    startTracker(): void {
        BackgroundGeolocation.deleteAllLocations();
        BackgroundGeolocation.start();
    }

    setCurrentLocation(location: {latitude:string, longitude:string}) {
        this.events.publish('BackgroundGeolocationService:setCurrentLocation', location);
    }

    stopTracking(): void {
        clearInterval(this.trackerInterval);
        BackgroundGeolocation.getLocations().then(locations => {
            this.locations = locations;
            if (locations.length != 0) {
                this.setCurrentLocation(locations[locations.length-1]);
            }
        }).catch(error => {
            this.trace.error(error);
        });
        BackgroundGeolocation.stop();
    }
}

Answer 1

您可以通过添加依赖于它的APP_INITIALIZER提供程序来强制执行它

{ provide: APP_INITIALIZER,
      useFactory: (config: BackgroundGeolocationService) => () => Promise.resolve(null),
      deps: [BackgroundGeolocationService], 
      multi: true }

如何强制angular2创建提供程序的实例？

1 个答案: