您能告诉我为什么以下功能在首次加载时有很大的延迟?在第二次正常的时间。同样的延迟也在实际设备上。请参见附带的视频。
注意:这里的问题是firebase绑定 this.eventData.getEventList().on('value', snapshot => {}
时,当我删除它时,一切正常。你知道如何做不同的操作吗?
视频: 有关此问题的视频
.html
<ion-card *ngFor="let event of eventList" (click)="goToEventDetail(event.id)" color="secondary">
<ion-card-content>
<p>Event Name: <strong>{{event?.name}}</strong></p>
<p>Ticket: <strong>${{event?.price}}</strong></p>
<p>Cost: <strong>${{event?.cost}}</strong></p>
<p>Date: <strong>{{event?.date}}</strong></p>
</ion-card-content>
</ion-card>
.ts
import { Component } from '@angular/core';
import { NavController } from 'ionic-angular';
import { EventDetailPage } from '../event-detail/event-detail';
import { EventData } from '../../providers/event-data';
@Component({
selector: 'page-event-list',
templateUrl: 'event-list.html',
})
export class EventListPage {
public eventList: any;
constructor(public navCtrl: NavController, public eventData: EventData) {
}
ionViewDidEnter() {
this.eventData.getEventList().on('value', snapshot => {
let rawList = [];
snapshot.forEach(snap => {
rawList.push({
id: snap.key,
name: snap.val().name,
price: snap.val().price,
cost: snap.val().cost,
date: snap.val().date
});
});
this.eventList = rawList;
});
}
}
提供者.ts
import { Injectable } from '@angular/core';
import firebase from 'firebase';
@Injectable()
export class EventData {
public currentUser: any;
public eventList: any;
constructor() {
this.currentUser = firebase.auth().currentUser.uid;
this.eventList = firebase.database().ref('userProfile/' + this.currentUser + '/eventList');
}
getEventList(): any {
return this.eventList;
}
}
似乎未检测到变化。尝试将push
包装到NgZone::run()
中。
首先,导入ngzone:
import { NgZone } from '@angular/core';
然后,在构造函数上注入:
constructor(public zone: NgZone /* ... other injections ... */) {
// constructor code ...
}
然后使用运行函数将数据推入数组:
snapshot.forEach(snap => {
this.zone.run(() => {
rawList.push({
id: snap.key,
name: snap.val().name,
price: snap.val().price,
cost: snap.val().cost,
date: snap.val().date
});
});
});
我不确定这是否对您有用,但值得一试。