本机脚本：ListView不显示项目

Question

我正在尝试在ListView中显示聊天列表，但没有显示任何项目，我试图查看Nativescript文档，并且安装程序是这样的，但没有任何显示。 我已经尝试过使用实时数据和虚拟数据。 使用实时数据时，我可以看到它到达了。

这是我的组件代码：

XML：

<ListView
        height="90%"
        margin-bottom="50"
        padding="5"
        [items]="chat | async"
        #list
    >

        <ng-template let-item="item">
            <GridLayout columns="*" rows="auto" class="msg">
                <StackLayout
                    [class]="filter(item.uid)"
                    orientation="horizontal"
                    [horizontalAlignment]="align(item.uid)"
                >
                    <Image
                        [visibility]="showImage(item.uid)"
                        class="author-img"
                        stretch="aspectFill"
                        height="30"
                        width="30"
                        verticalAlignment="top"
                        src="~/images/k1.png"
                        col="1"
                    ></Image>
                    <Label
                        [text]="item.message"
                        class="msg_text"
                        textWrap="true"
                        verticalAlignment="top"
                    ></Label>
                </StackLayout>
            </GridLayout>
        </ng-template>
    </ListView>

打字稿：

import {
    Component,
    OnInit,
    ViewChild,
    ElementRef,
    OnChanges,
    SimpleChanges,
    NgZone,
    ChangeDetectionStrategy,
    AfterViewInit
} from '@angular/core';
import { Observable, pipe } from 'rxjs';
import { ListView } from 'tns-core-modules/ui/list-view';
import { TextField } from 'tns-core-modules/ui/text-field';
import { PageRoute, RouterExtensions } from 'nativescript-angular/router';
import { switchMap } from 'rxjs/operators';
import * as firebase from 'nativescript-plugin-firebase';
import { firestore } from 'nativescript-plugin-firebase';
import { IUser } from '~/app/_model/user';
import { IChatItem, EStatus, IMessage } from '../chat.component';
import { FirebaseService } from '~/app/shared/services/firebase.service';

@Component({
    selector: 'ns-chat-conversation',
    templateUrl: './chat-conversation.component.html',
    styleUrls: ['./chat-conversation.component.scss'],
    changeDetection: ChangeDetectionStrategy.OnPush,
})
export class ChatConversationComponent implements OnInit, OnChanges, AfterViewInit {

    public user: IUser = null;
    public chats$: Observable<IMessage[]> = null;
    public chatId: string = null;

    public processing: boolean = true;
    public list: ListView;
    public textfield: TextField;
    public chat: IChatItem = {
        user: {
            uid: '',
            name: '',
            email: '',
            userType: 0,
            institutionTitle: '',
            institutionId: null,
            fieldTitle: '',
            fieldId: null,
            level: '',
            rating: 0,
            startDate: new Date(),
            profilePictureSrc: null,
        },
        chatInfo: {
            subject: '',
            messages: [],
            status: EStatus.ACCEPTED,
            hoursLeft: 2,
            chatId: '',
        },
    };

    public chat$: Observable<IMessage[]> = null;
    public messages: IMessage[] = [];

    @ViewChild('list', { static: false }) lv: ElementRef;
    @ViewChild('textfield', { static: false }) tf: ElementRef;

    constructor(
        private _pageRoute: PageRoute,
        private ngZone: NgZone,
        private _firebaseService: FirebaseService
    ) {
        this._pageRoute.activatedRoute
            .pipe(switchMap((activatedRoute) => activatedRoute.params))
            .forEach((params) => {
                this.chatId = params.id;
            });

            firebase
                .getCurrentUser()
                .then((user) => {
                    const userDocument = firebase.firestore
                        .collection('users')
                        .doc(user.uid);

                    userDocument.get().then((doc) => {
                        this.user = {
                            uid: doc.data().uid,
                            name: doc.data().name,
                            email: doc.data().email,
                            userType: doc.data().userType,
                            institutionTitle: doc.data().institutionTitle,
                            institutionId: doc.data().institutionId,
                            fieldTitle: doc.data().fieldTitle,
                            fieldId: doc.data().fieldId,
                            level: doc.data().level,
                            rating: doc.data().rating,
                            startDate: doc.data().startDate,
                            profilePictureSrc: doc.data().profilePictureSrc,
                        };

                        this.chat$ = this._firebaseService.getChat$(
                            this.chatId,
                            this.user.uid
                        );

                        this.chats$ = this.chat$;

                        this.chat$.subscribe((dd) => {
                            this.messages = dd;
                            this.processing = false;
                        });

                    });
                })
                .catch((error) => console.log('Trouble in paradise: ' + error));

    }

    public ngOnInit(): void {}

    public ngOnChanges(simpleChanges: SimpleChanges): void {
        if ('chats$' in simpleChanges) {
            console.log('check it');
        }

}