如何使用Rx在Angular 2中实现可拖动的div

Question

我一直在尝试使用Angular 2来使用可拖动的div工作.我使用angular2-examples repo中的这个示例作为起点,只是真正调整代码来解释toRx()方法的删除.代码有效,但它不考虑mouseout事件.这意味着如果我单击一个Draggable div,然后慢慢移动鼠标,div将随鼠标移动.但是如果我移动鼠标的速度太快,mouseout则会发送一个mousemove事件而不是一个事件,拖动停止.

在鼠标移动到目前为止mouseout触发事件后,如何保持拖动？我已经尝试将mouseout事件流与mousemove一个事件流合并,以便将mouseout事件视为一个事件mousemove,但这不起作用.

我正在使用Angular 2.0.0-beta.12.

import {Component, Directive, HostListener, EventEmitter, ElementRef, OnInit} from 'angular2/core';
import {map, merge} from 'rxjs/Rx';

@Directive({
    selector: '[draggable]'
})
export class Draggable implements OnInit {

    mouseup = new EventEmitter();
    mousedown = new EventEmitter();
    mousemove = new EventEmitter();
    mouseout = new EventEmitter();

    @HostListener('mouseup', ['$event'])
    onMouseup(event) {
        this.mouseup.emit(event);
    }

    @HostListener('mousedown', ['$event'])
    onMousedown(event) {
        this.mousedown.emit(event);
        return false; // Call preventDefault() on the event
    }

    @HostListener('mousemove', ['$event'])
    onMousemove(event) {
        this.mousemove.emit(event);
    }

    @HostListener('mouseout', ['$event'])
    onMouseout(event) {
        this.mouseout.emit(event);
        return false; // Call preventDefault() on the event
    }

    constructor(public element: ElementRef) {
        this.element.nativeElement.style.position = 'relative';
        this.element.nativeElement.style.cursor = 'pointer';

        map;
        merge;
        this.mousedrag = this.mousedown.map(event => {
            return {
                top: event.clientY - this.element.nativeElement.getBoundingClientRect().top
                left: event.clientX - this.element.nativeElement.getBoundingClientRect().left,
            };
        })
        .flatMap(
            imageOffset => this.mousemove.merge(this.mouseout).map(pos => ({
                top: pos.clientY - imageOffset.top,
                left: pos.clientX - imageOffset.left
            }))
            .takeUntil(this.mouseup)
        );
    }

    ngOnInit() {
        this.mousedrag.subscribe({
            next: pos => {
                this.element.nativeElement.style.top = pos.top + 'px';
                this.element.nativeElement.style.left = pos.left + 'px';
            }
        });
    }
}

@Component({
    selector: 'my-app',
    template: `
        <div draggable>
            <h1>Hello, World!</h1>
        </div>
        `,
    directives: [Draggable,],
})
export class AppComponent {
}

Answer 1

我在RxJs中找到了答案如何处理文档事件.问题的关键是当鼠标悬停在该元素上时,鼠标事件仅发送到元素.所以我们确实希望mousedown事件仅限于特定元素,但我们必须跟踪全局 mousemove和mouseup事件.这是新代码.注意@HostListener装饰器的使用,onMouseup并onMousemove指定目标为document:mouseup和document:mousemove.这是全局事件通过管道传输到Rx流的方式.

HostListener的官方angular2文档没有提到这种target:eventName语法,但是这个2.0.0-alpha.24的旧dart文档确实提到了它.它似乎仍然在2.0.0-beta.12中工作.

@Directive({
    selector: '[draggable]'
})
export class Draggable implements OnInit {

    mouseup = new EventEmitter<MouseEvent>();
    mousedown = new EventEmitter<MouseEvent>();
    mousemove = new EventEmitter<MouseEvent>();

    mousedrag: Observable<{top, left}>;

    @HostListener('document:mouseup', ['$event'])
    onMouseup(event: MouseEvent) {
        this.mouseup.emit(event);
    }

    @HostListener('mousedown', ['$event'])
    onMousedown(event: MouseEvent) {
        this.mousedown.emit(event);
        return false; // Call preventDefault() on the event
    }

    @HostListener('document:mousemove', ['$event'])
    onMousemove(event: MouseEvent) {
        this.mousemove.emit(event);
    }

    constructor(public element: ElementRef) {
        this.element.nativeElement.style.position = 'relative';
        this.element.nativeElement.style.cursor = 'pointer';

        this.mousedrag = this.mousedown.map(event => {
            return {
                top: event.clientY - this.element.nativeElement.getBoundingClientRect().top
                left: event.clientX - this.element.nativeElement.getBoundingClientRect().left,
            };
        })
        .flatMap(
            imageOffset => this.mousemove.map(pos => ({
                top: pos.clientY - imageOffset.top,
                left: pos.clientX - imageOffset.left
            }))
            .takeUntil(this.mouseup)
        );
    }

    ngOnInit() {
        this.mousedrag.subscribe({
            next: pos => {
                this.element.nativeElement.style.top = pos.top + 'px';
                this.element.nativeElement.style.left = pos.left + 'px';
            }
        });
    }
}

Answer 2

你可以用这个: npm install ng2draggable

使用[ng2-draggable]="true",别忘了="true"

你可以在这里找到它

https://github.com/cedvdb/ng2draggable

这是代码:

@Directive({
  selector: '[ng2-draggable]'
})
export class Draggable implements OnInit{
    topStart:number=0;
    leftStart:number=0;
    _allowDrag:boolean = true;
    md:boolean;

    constructor(public element: ElementRef) {}

        ngOnInit(){
          // css changes
          if(this._allowDrag){
            this.element.nativeElement.style.position = 'relative';
            this.element.nativeElement.className += ' cursor-draggable';
          }
        }

        @HostListener('mousedown', ['$event'])
        onMouseDown(event:MouseEvent) {
          if(event.button === 2)
            return; // prevents right click drag, remove his if you don't want it
          this.md = true;
          this.topStart = event.clientY - this.element.nativeElement.style.top.replace('px','');
          this.leftStart = event.clientX - this.element.nativeElement.style.left.replace('px','');
        }

        @HostListener('document:mouseup')
        onMouseUp(event:MouseEvent) {
          this.md = false;
        }

        @HostListener('document:mousemove', ['$event'])
        onMouseMove(event:MouseEvent) {
          if(this.md && this._allowDrag){
            this.element.nativeElement.style.top = (event.clientY - this.topStart) + 'px';
            this.element.nativeElement.style.left = (event.clientX - this.leftStart) + 'px';
          }
        }

        @HostListener('touchstart', ['$event'])
        onTouchStart(event:TouchEvent) {
          this.md = true;
          this.topStart = event.changedTouches[0].clientY - this.element.nativeElement.style.top.replace('px','');
          this.leftStart = event.changedTouches[0].clientX - this.element.nativeElement.style.left.replace('px','');
          event.stopPropagation();
        }

        @HostListener('document:touchend')
        onTouchEnd() {
          this.md = false;
        }

        @HostListener('document:touchmove', ['$event'])
        onTouchMove(event:TouchEvent) {
          if(this.md && this._allowDrag){
            this.element.nativeElement.style.top = ( event.changedTouches[0].clientY - this.topStart ) + 'px';
            this.element.nativeElement.style.left = ( event.changedTouches[0].clientX - this.leftStart ) + 'px';
          }
          event.stopPropagation();
        }

        @Input('ng2-draggable')
        set allowDrag(value:boolean){
          this._allowDrag = value;
          if(this._allowDrag)
            this.element.nativeElement.className += ' cursor-draggable';
          else
            this.element.nativeElement.className = this.element.nativeElement.className
                                                    .replace(' cursor-draggable','');
        }
}