使用角度材質2表根據用戶當前位置顯示來自後端的結果

Question

這與Typescript getCurrent location and pass to backend to get the result and pass to Material Table data source幾乎是相同的問題，但是這個問題我只得到了如何獲取當前位置並傳遞到後端的答案，由libertyernie的答案作品。所以我問這一個...

這是問題： 我想使用Angular Material 2表來顯示餐廳（這是來自我的春季啓動後端）列表。根據他們在github上給出的教程，數據源必須是可觀察的，這是有道理的，因爲您可以對列進行排序或過濾數據。但是，當我嘗試與當前位置集成時，我不知道如何使其工作...

該方案與我鏈接的問題相同，即嘗試獲取用戶的當前位置，並且一旦它獲得（例如，lat=123和lon=123），我會將這兩個參數傳遞到我的後端地址：http://localhost:8080/api/search/location?lat=123&lon=123，這將返回一個餐廳列表，並且我需要以某種方式更改爲Observable，以使ExampleDataSource中的connect()函數有效。

下面的代碼是我已經嘗試過的，但是我失敗了，數據源沒有任何迴應。

import { Component, OnInit } from '@angular/core'; 
import { Http, Response, URLSearchParams } from '@angular/http'; 
import { DataSource } from '@angular/cdk'; 
import { BehaviorSubject } from 'rxjs/BehaviorSubject'; 
import { Observable } from 'rxjs/Observable'; 
import 'rxjs/add/operator/startWith'; 
import 'rxjs/add/observable/merge'; 
import 'rxjs/add/operator/map'; 
import { Restaurant } from '../restaurant/restaurant'; 
import { Category } from '../category/category'; 
import { RestaurantService } from '../restaurant/restaurant.service'; 


@Component({ 
    selector: 'app-home', 
    templateUrl: './home.component.html', 
    styleUrls: ['./home.component.css'] 
}) 
export class HomeComponent implements OnInit { 
    displayedColumns = ['Id', 'Name', 'Category', 'Address', 'City']; 
    exampleDatabase: ExampleHttpDatabase | null; 
    dataSource: ExampleDataSource | null; 
    location: CurrentLocation | null; 
    lat: any; 
    lon: any; 
    result: Promise<any>; 

    constructor(http: Http) { 
    this.exampleDatabase = new ExampleHttpDatabase(http); 
    this.dataSource = new ExampleDataSource(this.exampleDatabase); 
    this.location = new CurrentLocation(http); 
    } 

    ngOnInit() { 
    this.result = this.location.getCurrentLocation(this.lat, this.lon); 
    this.result.then(function(result){ 
     console.log(result._body); 
    }) 
    console.log(this.lat, this.lon); 
    this.dataSource.connect(); 
    } 
} 

export class ExampleHttpDatabase { 
    private restaurantUrl = 'api/restaurant'; // URL to web API 
    getRestaurants(): Observable<Restaurant[]> { 
    var result = this.http.get(this.restaurantUrl) 
     .map(this.extractData); 
    result.toPromise(); 
    return result; 
    } 

    extractData(result: Response): Restaurant[] { 
    return result.json().map(restaurant => { 
     return { 
     id: restaurant.id, 
     name: restaurant.restaurant_name, 
     category: restaurant.category.map(c => c.categoryName).join(','), 
     address: restaurant.address.address, 
     city: restaurant.address.city.city_name 
     } 
    }); 
    } 
    constructor(private http: Http) { } 
} 

export class CurrentLocation { 
    constructor(private http: Http) { } 
    private lat: any; 
    private lon: any; 
    private params = new URLSearchParams(); 
    private url = 'api/search/location'; 


    getPosition =() => { 
    var latitude, longitude; 
    return new Promise((resolve, reject) => { 
     navigator.geolocation.getCurrentPosition((position) => { 
     resolve(position.coords); 
     }, (err) => { 
     reject(err); 
     }); 
    }) 
    } 
    async getCurrentLocation(lat, lon): Promise<any> { 
    let coords = await this.getPosition(); 
    lat = this.lat = coords['latitude']; 
    lon = this.lon = coords['longitude']; 
    this.params.set('lat', this.lat); 
    this.params.set('lon', this.lon); 
    var result = this.http.get(this.url, { search: this.params }); 
    return await result.toPromise(); 
    } 
} 

export class ExampleDataSource extends DataSource<Restaurant> { 
    constructor(private _exampleDatabase: ExampleHttpDatabase) { 
    super(); 
    } 

    /** Connect function called by the table to retrieve one stream containing the data to render. */ 
    connect(): Observable<Restaurant[]> { 
    return this._exampleDatabase.getRestaurants(); 
    } 

    disconnect() { } 
} 

的完整代碼也Github上：https://github.com/zhengye1/Eatr/tree/dev

Answer 1

最後，我可以得到顯示到首頁的信息，但怪異的行爲情況發生，請訪問以下鏈接：Weird behavior when using Angular Material 2 table (Angular 2/Spring Boot backend)