我是Angular的新手，并且遇到了问题。任何人都可以帮助我弄清楚我在父组件中做错了什么。我无法在父项中获得子项引用。我已经遵循以下参考，但没有成功。
Angular 2 @ViewChild annotation returns undefined https://expertcodeblog.wordpress.com/2018/01/12/angular-resolve-error-viewchild-annotation-returns-undefined/
父母：
import { Component, OnInit, OnDestroy, ViewChild, HostListener, AfterViewInit, ViewChildren, QueryList } from '@angular/core';
import { Router, NavigationEnd, NavigationStart } from '@angular/router';
import { NavItem, NavItemType } from '../../md/md.module';
import { Subscription } from 'rxjs/Subscription';
import { Location, LocationStrategy, PathLocationStrategy, PopStateEvent } from '@angular/common';
import 'rxjs/add/operator/filter';
import { NavbarComponent } from '../../shared/navbar/navbar.component';
import PerfectScrollbar from 'perfect-scrollbar';
import { ChatService } from 'app/services/chat.service';
import swal from 'sweetalert2';
import { JitsiService } from 'app/services/jitsi.service';
import { UserService } from 'app/services/user.service';
import { ConferenceStudentComponent } from 'app/conference-student/conference-student.component';
declare const $: any;
@Component({
selector: 'app-layout',
templateUrl: './admin-layout.component.html'
})
export class AdminLayoutComponent implements OnInit, AfterViewInit {
public navItems: NavItem[];
private _router: Subscription;
private lastPoppedUrl: string;
private yScrollStack: number[] = [];
url: string;
location: Location;
@ViewChild('sidebar') sidebar: any;
@ViewChild(NavbarComponent) navbar: NavbarComponent;
@ViewChildren(ConferenceStudentComponent) stuConf: QueryList<ConferenceStudentComponent>;
constructor( private router: Router, location: Location,
private chatService: ChatService,
private jitsiService: JitsiService,
private userService: UserService
) {
this.location = location;
this.chatService.callVisibilityChange
.subscribe(callFrom => {
console.log('admin layout call from', callFrom);
if (callFrom) {
this.userService.getLoggedUserDetail()
.subscribe(loggedUser => {
if (!loggedUser) {
console.log(`Invalid token, logged user data not fetched`);
return false;
}
this.userService.getUser(callFrom['fromUser'])
.subscribe(otherUser => {
swal({
title: `${otherUser['fullName']} is calling`,
text: `Click on accept to join session`,
type: `info`,
showCancelButton: true,
cancelButtonColor: `#d33`,
cancelButtonText: `reject`,
confirmButtonColor: `#3085d6`,
confirmButtonText: `accept`
}).then((result) => {
if (result.value) {
const jitsiSessionData = {
loggedUser,
otherUser,
roomName: callFrom['roomName']
}
this.router.navigateByUrl(`/conference-student/${otherUser['_id']}`);
window.setTimeout(() => this.jitsiService.joinSession(jitsiSessionData), 10000);
} else {
console.log('user select rejected');
this.chatService.jitsiCallReject(otherUser._id, loggedUser._id, callFrom['roomName']);
}
})
});
});
}
});
}
ngOnInit() {
const elemMainPanel = <HTMLElement>document.querySelector('.main-panel');
const elemSidebar = <HTMLElement>document.querySelector('.sidebar .sidebar-wrapper');
this.location.subscribe((ev:PopStateEvent) => {
this.lastPoppedUrl = ev.url;
});
this.router.events.subscribe((event:any) => {
if (event instanceof NavigationStart) {
if (event.url != this.lastPoppedUrl)
this.yScrollStack.push(window.scrollY);
} else if (event instanceof NavigationEnd) {
if (event.url == this.lastPoppedUrl) {
this.lastPoppedUrl = undefined;
window.scrollTo(0, this.yScrollStack.pop());
}
else
window.scrollTo(0, 0);
}
});
this._router = this.router.events.filter(event => event instanceof NavigationEnd).subscribe((event: NavigationEnd) => {
elemMainPanel.scrollTop = 0;
elemSidebar.scrollTop = 0;
});
const html = document.getElementsByTagName('html')[0];
if (window.matchMedia(`(min-width: 960px)`).matches && !this.isMac()) {
let ps = new PerfectScrollbar(elemMainPanel);
ps = new PerfectScrollbar(elemSidebar);
html.classList.add('perfect-scrollbar-on');
}
else {
html.classList.add('perfect-scrollbar-off');
}
this._router = this.router.events.filter(event => event instanceof NavigationEnd).subscribe((event: NavigationEnd) => {
this.navbar.sidebarClose();
});
this.navItems = [
{ type: NavItemType.NavbarLeft, title: 'Dashboard', iconClass: 'fa fa-dashboard' },
{
type: NavItemType.NavbarRight,
title: '',
iconClass: 'fa fa-bell-o',
numNotifications: 5,
dropdownItems: [
{ title: 'Notification 1' },
{ title: 'Notification 2' },
{ title: 'Notification 3' },
{ title: 'Notification 4' },
{ title: 'Another Notification' }
]
},
{
type: NavItemType.NavbarRight,
title: '',
iconClass: 'fa fa-list',
dropdownItems: [
{ iconClass: 'pe-7s-mail', title: 'Messages' },
{ iconClass: 'pe-7s-help1', title: 'Help Center' },
{ iconClass: 'pe-7s-tools', title: 'Settings' },
'separator',
{ iconClass: 'pe-7s-lock', title: 'Lock Screen' },
{ iconClass: 'pe-7s-close-circle', title: 'Log Out' }
]
},
{ type: NavItemType.NavbarLeft, title: 'Search', iconClass: 'fa fa-search' },
{ type: NavItemType.NavbarLeft, title: 'Account' },
{
type: NavItemType.NavbarLeft,
title: 'Dropdown',
dropdownItems: [
{ title: 'Action' },
{ title: 'Another action' },
{ title: 'Something' },
{ title: 'Another action' },
{ title: 'Something' },
'separator',
{ title: 'Separated link' },
]
},
{ type: NavItemType.NavbarLeft, title: 'Log out' }
];
}
ngAfterViewInit() {
this.runOnRouteChange();
this.stuConf.changes.subscribe((comp: QueryList<ConferenceStudentComponent>) => {
console.log(`student component`, comp);
})
}
public isMap() {
if (this.location.prepareExternalUrl(this.location.path()) === '/maps/fullscreen') {
return true;
} else {
return false;
}
}
runOnRouteChange(): void {
if (window.matchMedia(`(min-width: 960px)`).matches && !this.isMac()) {
const elemSidebar = <HTMLElement>document.querySelector('.sidebar .sidebar-wrapper');
const elemMainPanel = <HTMLElement>document.querySelector('.main-panel');
let ps = new PerfectScrollbar(elemMainPanel);
ps = new PerfectScrollbar(elemSidebar);
ps.update();
}
}
isMac(): boolean {
let bool = false;
if (navigator.platform.toUpperCase().indexOf('MAC') >= 0 || navigator.platform.toUpperCase().indexOf('IPAD') >= 0) {
bool = true;
}
return bool;
}
}
孩子：
import { Component, OnInit } from '@angular/core';
import { ActivatedRoute, ParamMap } from '@angular/router';
import '../../vendor/jitsi/external_api.js';
import { JitsiService } from 'app/services/jitsi.service.js';
import { UserService, UserSchema } from 'app/services/user.service.js';
import swal from 'sweetalert2';
declare var JitsiMeetExternalAPI: any;
declare const $: any;
@Component({
selector: "app-conference-student-cmp",
templateUrl: "conference-student.component.html"
})
export class ConferenceStudentComponent implements OnInit {
roomName: string;
tutor: UserSchema
student: UserSchema;
domain: string;
options: any;
api: any;
hasActiveRoom: boolean;
tutorId: string;
conferenceJoined: boolean;
constructor(
private route: ActivatedRoute,
private jitsiService: JitsiService,
private userService: UserService
) { }
ngOnInit() {
this.conferenceJoined = false;
// this.domain = "jitsi.liquidclouds.in";
this.domain = 'meet.jit.si';
this.route.paramMap.subscribe((params: ParamMap) => this.tutorId = params.get('id'));
this.userService
.getLoggedUserDetail()
.subscribe(student => {
// store student
this.student = student;
this.userService.getUser(this.tutorId)
.subscribe((tutor: UserSchema) => {
// store tutor
this.tutor = tutor;
const obj = { tutorId: this.tutor['_id'], studentId: this.student['_id'] };
this.jitsiService.getActiveRoomForStudent(obj).subscribe(resp => {
if (resp && resp['result'] && resp['result']['roomName']) {
this.hasActiveRoom = true;
this.roomName = resp['result']['roomName'];
}
});
});
});
}
joinSession() {
this.options = {
roomName: this.roomName,
width: 800,
height: 500,
parentNode: document.querySelector('#jitsiVideo'),
configOverwrite: {},
interfaceConfigOverwrite: {
// filmStripOnly: true,
TOOLBAR_BUTTONS: [
'microphone', 'camera', 'closedcaptions', 'desktop', 'fullscreen',
'hangup', 'profile', 'chat', 'recording'
],
}
};
this.api = new JitsiMeetExternalAPI(this.domain, this.options);
this.api.executeCommand('displayName', this.student['fullName']);
this.api.addEventListeners({
readyToClose: this.unload,
participantLeft: this.handleParticipantLeft,
participantJoined: this.handleParticipantJoined,
videoConferenceJoined: this.handleVideoConferenceJoined,
videoConferenceLeft: this.handleVideoConferenceLeft
});
this.conferenceJoined = true;
}
unload = () => {
if (this.api instanceof JitsiMeetExternalAPI) {
this.api.dispose();
}
$('#jitsiVideo').html('');
this.conferenceJoined = false;
this.hasActiveRoom = false;
}
handleParticipantLeft = (arg) => {
this.jitsiService.getJitsiDetailByParticipantId(arg.id)
.subscribe(async roomDetail => {
if (!roomDetail) {
console.log(`No room is joined by the participant id: ${arg.id}`);
return false;
} else {
const participantDetail = roomDetail['participants'].filter(el => el.jitsiParticipantId === arg.id)[0];
if (participantDetail) {
switch (participantDetail.type) {
case 'manager':
console.log('Left participant is manager');
break;
case 'supervisor':
console.log('Left participant is supervisor');
break;
case 'student':
console.log('Left participant is student');
break;
case 'tutor':
console.log('Left participant is tutor');
this.api.dispose();
this.conferenceJoined = false;
this.hasActiveRoom = false;
alert('Tutor left the session.');
break;
default:
console.log('Left participant is not a valid type');
break;
}
}
}
});
}
handleParticipantJoined = (arg) => {
console.log('participant joined: ', arg, this.api);
}
handleVideoConferenceJoined = (arg) => {
const obj = {
participantId: arg.id,
roomName: arg.roomName,
tutorId: this.tutor['_id'],
studentId: this.student['_id'],
studentJoined: 'yes',
joineeType: 'student',
}
// save new room
this.jitsiService.updateJitsiRoomForStudent(obj);
}
handleVideoConferenceLeft = (arg) => {
}
}
admin-layout.componet.html
<div class="wrapper">
<div class="sidebar" data-color="rose" data-background-color="white" data-image="./assets/img/sidebar-1.jpg">
<app-sidebar-cmp></app-sidebar-cmp>
<div class="sidebar-background" style="background-image: url(assets/img/sidebar-1.jpg)"></div>
</div>
<div class="main-panel">
<router-outlet></router-outlet>
<div *ngIf="!isMap()">
<app-footer-cmp></app-footer-cmp>
</div>
</div>
<app-fixedplugin></app-fixedplugin>
</div>