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 使可拖动的 div 工作 2. 我使用 this example from the angular2-examples repo 作为起点，只是真正调整代码以说明删除 toRx() 方法。该代码有效，但不考虑 mouseout 事件。这意味着如果我点击一个 Draggable div，然后慢慢移动鼠标，div 将随着鼠标移动。但是，如果我将鼠标移动得太快，则会发送 mouseout 事件而不是 mousemove 事件，并且拖动会停止。

如何在鼠标移动到触发 mouseout 事件后继续拖动？我已经尝试将 mouseout 事件流与 mousemove 事件流合并，这样 mouseout 事件就像 mousemove 事件一样被处理，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

您可以创建一个覆盖屏幕空间的大 div。首先，div 的 z-index 低于您要拖动的 div。在收到 mousedown 后，您将 div 的 z-index 更改为高于拖动元素并在此 div 上接收鼠标移动事件。您可以使用它来计算拖动元素的位置。然后，您可以停止并在收到鼠标弹起时再次发送 div。

我最近在Angular2 中编写了一个模块化的拖放框架。请试一试并提供反馈。

https://github.com/ivegotwings/ng2Draggable

但是，一旦触发 mouseout 事件，我就会停止拖动。

Answer 2

我在中找到了答案。问题的症结在于鼠标事件仅在鼠标悬停在该元素上时才发送到该元素。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 global mousemove 和 mouseup 事件。这是新代码。注意 onMouseup 和 onMousemove 上 @HostListener 装饰器的使用将目标指定为 document:mouseup 和 document:mousemove。这就是全局事件通过管道传输到 Rx 流中的方式。

official angular2 documentation for HostListener doesn't mention this target:eventName syntax, but this old dart documentation for 2.0.0-alpha.24确实提到了它。它似乎在 2.0.0-beta.12 中仍然有效。

@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 3

你可以使用这个：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

代码如下：

@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','');
        }
}

Answer 4

我对可拖动弹出窗口有同样的问题，所以我在 mousedown 上添加 mousemove 和 mouseup 事件到文档中，并在 mouseup 上删除它们。我使用动态添加和删除事件侦听器。

模板：

<div class="popup-win" (mousedown)="mousedown($event)"></div>

组件：

constructor(private elementRef: ElementRef,
        private renderer: Renderer2) {}

mousedown(event: any) {
    this.xStartElementPoint = this.curX;
    this.yStartElementPoint = this.curY;
    this.xStartMousePoint = event.pageX;
    this.yStartMousePoint = event.pageY;
    this.mousemoveEvent = this.renderer.listen("document", "mousemove", this.dragging);
    this.mouseupEvent = this.renderer.listen("document", "mouseup", this.mouseup);
}

dragging(event: any) {
     this.curX = this.xStartElementPoint + (event.pageX - this.xStartMousePoint);
     this.curY = this.yStartElementPoint + (event.pageY - this.yStartMousePoint);
}
mouseup(event: any) {
    // Remove listeners
    this.mousemoveEvent();
    this.mouseupEvent();
}

这是 Plunker 上的可运行示例。

如何使用 Rx 在 Angular 2 中实现可拖动的 div

How to implement a draggable div in Angular 2 using Rx

angular

angular2-directives

rxjs5