[英]Weird behavior when using Angular Material 2 table (Angular 2/Spring Boot backend)
继续至使用角度材料2表,以根据用户当前位置显示来自后端的结果
我编写此代码的目的是当用户进入站点时,它将尝试询问用户当前位置。 一旦我的前端获得当前的经度/纬度,它将根据用户的位置传递到后端以获取最近的餐厅,并使用角度材质表进行显示。 但是,当我在Chrome上进行测试时,我的行为很奇怪,首页不会在第一时间立即显示结果,请尝试刷新,不起作用,唯一可行的方法是切换另一个标签,然后再回到此标签,它将在角度材质表中显示结果。
这是home.component.ts的代码
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 'rxjs/add/observable/frompromise';
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'];
dataSource: ExampleDataSource | null;
constructor(http: Http) {
//this.exampleDatabase = new ExampleHttpDatabase(http, this.location);
this.dataSource = new ExampleDataSource(http);
}
ngOnInit() {
this.dataSource.connect();
}
}
export class ExampleDataSource extends DataSource<Restaurant> {
private url = 'api/search/location';
private params = new URLSearchParams();
private lat;
private lon;
constructor(private http: Http) {
super();
}
/** Connect function called by the table to retrieve one stream containing the data to render. */
connect(): Observable<Restaurant[]> {
// var location;
// if (navigator.geolocation){
// var options = {timeout: 60000};
// location = navigator.geolocation.getCurrentPosition((position)=>{
// return position;
// },(err) =>{
// console.log("Error")
// }, options);
// }
// console.log("Locations: " + location);
var result = this.getCurrentLocation().then((res) =>
{
return res;
});
return Observable.fromPromise(result);
}
disconnect() { }
getPosition = () => {
var latitude, longitude;
return new Promise((resolve, reject) => {
navigator.geolocation.getCurrentPosition((position) => {
resolve(position.coords);
}, (err) => {
reject(err);
});
})
}
async getCurrentLocation(): Promise<Restaurant[]> {
let coords = await this.getPosition();
this.lat = coords['latitude'];
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 }).map(this.extractData);
return await result.toPromise();
}
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.cityName
}
});
}
}
我不知道我做错了..有人可以帮助我吗? 有关完整代码,请参见https://github.com/zhengye1/Eatr/tree/dev
终于解决了...
我要做的只是将HomeComponent类上的ngOnInit更改为以下内容
async ngOnInit() {
await this.dataSource.connect();
}
而且有效..不知道为什么...
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