我面临一个非常奇怪的问题。我在* ngIf中使用了Observable来显示错误以及异步管道。
问题在于,当Observable的值更新时,DOM也不会更新。仅当我单击页面或使用键盘获得焦点时,它才会更新。
那么,我应该如何将Observable与DOM绑定?
我尝试了各种方法来使用* ngIf,如果在* ngIf中使用if绑定DOM(带有或不带有异步管道等)来绑定DOM。
这就是我在HTML中使用的方式。
<div style="font-size: 0.9rem;" *ngIf="messageInfo | async"
[ngClass]="{ 'alert': message, 'alert-success': message.type === 'success',
'alert-danger': message.type === 'error' }">{{message.text}}
<span (click)="close()" style="cursor: pointer; float: right;">
<i class="material-icons icon-20 vertical-bottom">close</i>
</span>
</div>
组件代码
export class AlertComponent implements OnInit {
message: any;
messageInfo: Observable<any>;
constructor(private alertService: AlertService) {
}
ngOnInit() {
this.messageInfo = this.alertService.getMessage();
this.messageInfo.subscribe(message => {
this.message = message;
});
}
close() {
this.alertService.close();
this.message = undefined;
}
}
服务
export class AlertService {
private subject = new BehaviorSubject<any>(null);
private keepAfterNavigationChange = false;
constructor(private router: Router) {
// clear alert message on route change
router.events.subscribe(event => {
if (event instanceof NavigationStart) {
if (this.keepAfterNavigationChange) {
// only keep for a single location change
this.keepAfterNavigationChange = false;
} else {
// clear alert
this.subject.next(null);
}
}
});
}
success(message: string, keepAfterNavigationChange = false) {
this.keepAfterNavigationChange = keepAfterNavigationChange;
this.subject.next({type: 'success', text: message});
// to hide message after 3 seconds.
setTimeout(() => {
this.close();
}, 3000);
}
error(message: string, keepAfterNavigationChange = false) {
this.keepAfterNavigationChange = keepAfterNavigationChange;
this.subject.next({type: 'error', text: message});
// to hide message after 3 seconds.
setTimeout(() => {
this.close();
}, 3000);
}
getMessage(): Observable<any> {
return this.subject.asObservable();
}
close() {
this.subject.next(null);
}
}
我以这种方式在所有其他组件中使用它:
<alert></alert>
我希望根据Observable的值更新UI,而无需单击或关注页面。不幸的是,只有当我使用鼠标或键盘专注于页面时,它才会更新。
答案 0 :(得分:0)
按照以下建议更新ngZone内部的变量: 在您的情况下应该是这样的:
public constructor(private _ngZone: NgZone) {}
this.messageInfo.subscribe(message => {
this._ngZone.run(() => {
this.message = message;
});
});
https://github.com/angular/angular/issues/7381#issuecomment-191456151
如果这不起作用,您可以尝试使用:
import { ChangeDetectorRef } from '@angular/core';
public constructor(private cdr: NgZone) {}
this.messageInfo.subscribe(message => {
this.message = message;
this.cdr.markForCheck();
});
答案 1 :(得分:0)
您可以尝试关注-
从组件中删除message
变量
并删除this.messageInfo.subscribe
行
然后像这样更新您的模板。
<div style="font-size: 0.9rem;" *ngIf="(messageInfo | async) as message"
[ngClass]="{ 'alert': message, 'alert-success': message.type === 'success',
'alert-danger': message.type === 'error' }">{{message.text}}
<span (click)="close()" style="cursor: pointer; float: right;">
<i class="material-icons icon-20 vertical-bottom">close</i>
</span>
</div>