Angular 2: Get position of HTML element

问题:

I'm trying to implement a custom directive in Angular 2 for moving an arbitrary HTML element around. So far everything is working except that I don't now how to get the initial position of the HTML element when I click on it and want to start moving. I'm binding to the top and left styles of my HTML element with those two host bindings:

/** current Y position of the native element. */
@HostBinding('style.top.px') public positionTop: number;

/** current X position of the native element. */
@HostBinding('style.left.px') protected positionLeft: number;

The problem is that both of them are undefined at the beginning. I can only update the values which will also update the HTML element but I cannot read it? Is that suppose to be that way? And if yes what alternative do I have to retrieve the current position of the HTML element.

回答1:

<div (click)="move()">xxx</div>

// get the host element
constructor(elRef:ElementRef) {}

move(ref: ElementRef) {
  console.log(this.elRef.nativeElement.offsetLeft);
}

See also https://stackoverflow.com/a/39149560/217408

回答2:

In typeScript you can get the position as follows:

@ViewChild('ElementRefName') element: ElementRef;

const {x, y} = this.element.nativeElement.getBoundingClientRect();

回答3:

in html:

<div (click)="getPosition($event)">xxx</div>

in typescript:

getPosition(event){
    let offsetLeft = 0;
    let offsetTop = 0;

    let el = event.srcElement;

    while(el){
        offsetLeft += el.offsetLeft;
        offsetTop += el.offsetTop;
        el = el.parentElement;
    }
    return { offsetTop:offsetTop , offsetLeft:offsetLeft }
}