Ionic2“ionViewDidEnter”方法第一次很慢

Question

你能告诉我为什么下面的功能在首次加载时会有很大的延迟吗？第二次正常。实际设备上也有同样的延迟。请看附件视频。

注意： 这里的问题是 firebase bind this.eventData.getEventList().on('value', snapshot => {} 当我删除它时一切正常。你知道怎么做吗？

视频： Video about this issue

.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;
    });
  }
}

provider.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;
  }

}

Answer 1

似乎没有检测到更改。尝试将您的 push 包装成 NgZone::run()。

首先，导入 NgZone：

import { NgZone } from '@angular/core';

然后，注入你的构造函数：

constructor(public zone: NgZone /* ... other injections ... */) {
    // constructor code ...
}

然后使用run函数将数据压入数组：

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
        });
    });
});

我不确定这是否适合你，但值得一试。