[英]Angular 4 @HostBinding('attr.id') does not work (undefined)
[英]Angular 2 does not detect changes for @HostBinding
我使用@HostBinding
與Chrome的拖放API一起設置一個類,如下所示:
@Directive({ selector: '[sortable-article]' })
export class SortableArticleComponent {
@HostBinding('class.dragged-element')
isDraggedArticle: boolean = false;
constructor(elRef: ElementRef, private ref: ChangeDetectorRef, private appRef: ApplicationRef, private dndService: ArticleDndService) {
this.el = elRef.nativeElement;
Observable.fromEvent(this.el, 'dragstart').subscribe(e => this.onDragStart(<DragEvent> e));
Observable.fromEvent(this.el, 'drop').subscribe(e => this.onDrop(<DragEvent> e));
}
onDragStart(event: DragEvent) {
this.isDraggedArticle = true;
}
onDrop(event: DragEvent) {
event.preventDefault();
this.isDraggedArticle = false;
}
}
發生的事情是,更多次然后不是, isDraggedArticle
類沒有從元素中移除,我也不知道為什么。 我嘗試添加
this.ref.detectChanges();
this.appRef.tick();
到onDrop方法(其中ref
是一個ChangeDetectorRef
和appRef
是ApplicationRef
),但它並不能幫助。
Ich認為我找到了解決問題的方法: drop
事件不是在已拖動的項目上觸發的,而是在放置到其上的項目上觸發的。 這意味着this.isDraggedArticle = false
在drop回調中設置this.isDraggedArticle = false
,我需要在dragend
回調中進行設置:
@Directive({ selector: '[sortable-article]' })
export class SortableArticleComponent {
@HostBinding('class.dragged-element')
isDraggedArticle: boolean = false;
constructor(elRef: ElementRef, private ref: ChangeDetectorRef, private appRef: ApplicationRef, private dndService: ArticleDndService) {
this.el = elRef.nativeElement;
Observable.fromEvent(this.el, 'dragstart').subscribe(e => this.onDragStart(<DragEvent> e));
Observable.fromEvent(this.el, 'dragend').subscribe(e => this.onDragEnd(<DragEvent> e));
}
onDragStart(event: DragEvent) {
this.isDraggedArticle = true;
}
onDragEnd(event: DragEvent) {
this.isDraggedArticle = false;
}
}
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