Angular Drag and Drop Directives Overview

    The Ignite UI for Angular Drag and Drop directives enable dragging of elements around the page. The supported features include free dragging, using a drag handle, drag ghost, animations and multiple drop strategies.

    Angular Drag and Drop Example

    Drag and drop icon to reposition it.

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    Getting Started with Ignite UI for Angular Drag and Drop

    To get started with the Ignite UI for Angular Drag and Drop directives, first you need to install Ignite UI for Angular. In an existing Angular application, type the following command:

    ng add igniteui-angular
cmd

    For a complete introduction to the Ignite UI for Angular, read the getting started topic.

    The next step is to import the IgxDragDropModule in your app.module.ts file.

    // app.module.ts

...
import { IgxDragDropModule } from 'igniteui-angular';
// import { IgxDragDropModule } from '@infragistics/igniteui-angular'; for licensed package

@NgModule({
    ...
    imports: [..., IgxDragDropModule],
    ...
})
export class AppModule {}
typescript

    Alternatively, as of 16.0.0 you can import the IgxDragDirective and IgxDropDirective as standalone dependencies, or use the IGX_DRAG_DROP_DIRECTIVES token to import the component and all of its supporting components and directives.

    // home.component.ts

import { IGX_DRAG_DROP_DIRECTIVES } from 'igniteui-angular';
// import { IGX_DRAG_DROP_DIRECTIVES } from '@infragistics/igniteui-angular'; for licensed package

@Component({
    selector: 'app-home',
    template: `
    <div igxDrag>Drag me</div>
    <div igxDrop>Drop here</div>
    `,
    styleUrls: ['home.component.scss'],
    standalone: true,
    imports: [IGX_DRAG_DROP_DIRECTIVES]
    /* or imports: [IgxDragDirective, IgxDropDirective] */
})
export class HomeComponent {}
typescript

    Now that you have the Ignite UI for Angular Drag and Drop module or directives imported, you can start using the igxDrag and igxDrop directives.

    Using the Angular Drag Directive

    When an element inside your Angular application needs to be dragged from one place to another on the page, the igxDrag directive is designed to help achieve this behavior. In combination with the igxDrop directive, the placing of the dragged element can be done as well, so you can have fully interactive application.

    Dragging Fundamentals

    A drag operation starts when the end user swipes at least 5px in any direction. This is customizable and can be changed using the dragTolerance input. Otherwise the interaction is considered as a click and a dragClick event is triggered.

    When the dragging starts, the dragStart event is triggered. To prevent any actual movement to occur, the event can be canceled by setting the cancel property to true.

    Before any actual movement is about to be performed, the dragMove event is also triggered, containing the last and next position of the pointer. It is triggered every time a movement is detected while dragging an element around.

    After the user releases the mouse/touch the drag ghost element is removed from the DOM and the dragEnd event will be emitted.

    Due to the nature of the dragMove event, it can be triggered many times in a short period of time, which may cause performance issues for complex operations done when triggered.

    Dragging With Ghost

    The igxDrag directive can be applied on any DOM element by just adding it to its template.

    <div igxDrag>Drag me</div>
html

    The default behavior of igxDrag directive is to leave the base element unmodified and to create a ghost element when drag operation is performed by the end user.

    Before the ghost is rendered on the page, a ghostCreate event is triggered containing information of the ghost element that is about to be added. The event is triggered right after the dragStart event. If the dragStart is canceled, no ghost will be created and the ghostCreate event will not trigger accordingly.

    Right before the ghost is about to be removed, the ghostDestroy event will be triggered.

    Customizing The Ghost

    The ghost element by default is a copy of the base element the igxDrag is used on. It can be customized by providing a template reference to the ghostTemplate input directly.

    <div class="email-content flexlist"
	igxDrag
	[ghostTemplate]="customGhost">
	<div class="sender">
		{{email.sender}} 
	</div>
	<div class="email-title">
		{{email.title}}
	</div>
</div>
<ng-template #customGhost>
	<div class="dragGhost">
		<igx-icon fontSet="material">email</igx-icon> 
		Moving {{ draggedElements }} item{{ (draggedElements > 1 ? 's' : '')}}
	</div>
</ng-template>

html

    Dragging Without Ghost

    If you would like to move the base element, to which the igxDrag directive is applied, you can do that by setting the ghost input to false. That way there will be no extra ghost element rendered and if you need to apply custom styling when dragging and element, you can apply it directly to the base element.

    <div igxDrag [ghost]="false">Drag me</div>
html

    Dragging Using a Handle

    You can specify an element that is a child of the igxDrag by which to drag, since by default the whole element is used to perform that action. It can be done using the igxDragHandle directive and can be applied to multiple elements inside the igxDrag.

    <div
    igxDrag 
    [ghost]="false"
    [dragTolerance]="0"
    (dragMove)=onDragMove($event)>
    <igx-icon igxDragHandle fontSet="material" class="dialogHandle">drag_indicator</igx-icon>
    <div class="igx-dialog__window">
    </div>
</div>
html

    Drag the dialog using the handle in the following demo.

    EXAMPLE
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    Animations

    When an element is being dragged, there are no animations applied by default.

    You can apply transition animation to the igxDrag at any time, but it is advised to use it when dragging ends or the element is not currently dragged. This can be achieved by using the transitionToOrigin and the transitionTo methods.

    The transitionToOrigin method, as the name suggests, animates the currently dragged element or its ghost to the start position, where the dragging began. The transitionTo method animates the element to a specific location relative to the page (i.e. pageX and pageY) or to the position of a specified element. If the element is not being currently dragged, it will animate anyway or create ghost and animate it to the desired position.

    Both functions have arguments that you can set to customize the transition animation and set duration, timing function or delay. If specific start location is set it will animate the element starting from there.

    When the transition animation ends, if a ghost is created, it will be removed and the igxDrag directive will return to its initial state. If no ghost is created, it will keep its position. In both cases, then the transitioned event will be triggered, depending on how long the animation lasts. If no animation is applied, it will be triggered instantly.

    You can have other types of animations that involve element transformations. That can be done like any other element either using the Angular Animations or straight CSS Animations to either the base igxDrag element or its ghost. If you want to apply them to the ghost, you would need to define a custom ghost and apply animations to its element.

    Reorder items in the list using the drag handle. While dragging a list item other list items will re-order with animation.

    EXAMPLE
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    Ignoring draggable elements

    If the user wants to have interactable children of the main element which have igxDrag instanced, he can set the igxDragIgnore directive in order to make them be ignored by the igxDrag and not perform any dragging action. This will leave these elements be fully interactable and receive all mouse events.

    <div [igxDrag]="myData">
    <span>Drag me!</span>
    <igx-icon igxDragIgnore fontSet="material" (click)="remove()">bin</igx-icon>
</div>
html

    Using the Angular Drop Directive

    When an element that is being dragged using the igxDrag directive needs to be placed in an area, the igxDrop can be used to achieve this behavior. It provides events that you can use to determine if an element is entering the boundaries of the element it is applied to and if it is being released inside it.

    The igxDrop directive can be applied to any DOM element just like the igxDrag directive.

    By default, the igxDrop directive doesn't apply any logic for modifying the dragged element position in the DOM. That's why you need to specify a dropStrategy or apply custom logic. Drop strategies are discussed in the next section.

    Drop Strategies

    The igxDrop comes with 4 drop strategies which are: Default, Prepend, Insert and Append:

    • Default - does not perform any action when an element is dropped onto an igxDrop element and is implemented as a class named IgxDefaultDropStrategy.

    • Append - always inserts the dropped element as a last child and is implemented as a class named IgxAppendDropStrategy.

    • Prepend - always inserts the dropped element as first child and is implemented as a class named IgxPrependDropStrategy.

    • Insert - inserts the dragged element at last position. If there is a child under the element when it was dropped though, the igxDrag instanced element will be inserted at that child's position and the other children will be shifted. It is implemented as a class named IgxInsertDropStrategy.

    The way a strategy can be applied is by setting the dropStrategy input to one of the listed classes above. The value provided has to be a type and not an instance, since the igxDrop needs to create and manage the instance itself.

    public appendStrategy = IgxAppendDropStrategy;
typescript
    <div igxDrop [dropStrategy]="appendStrategy"></div>
html

    Canceling a drop strategy

    When using a specific drop strategy, its behavior can be canceled in the dropped events by setting the cancel property to true. The dropped event is specific to the igxDrop. If you does not have drop strategy applied to the igxDrop canceling the event would have no side effects.

    Example:

    <div igxDrag></div>
<!-- ... -->
<div igxDrop (dropped)="onDropped($event)"></div>
html
    public onDropped(event) {
    event.cancel = true;
}
typescript

    If you would like to implement your own drop logic, we advise binding to the dropped event and execute your logic there or extend the IgxDefaultDropStrategy class.

    Linking Drag to Drop Element

    Using the dragChannel and dropChannel input on respectively igxDrag and igxDrop directives, you can link different elements to interact only between each other. For example, if an igxDrag element needs to be constrained so it can be dropped on specific igxDrop element and not all available, this can easily be achieved by assigning them the same channel.

    <div igxDrag [dragChannel]="['Mammals', 'Land']"> Human </div>
<div igxDrag [dragChannel]="['Mammals', 'Water']"> Dolphin </div>
<div igxDrag [dragChannel]="['Insects', 'Air']"> Butterfly </div>
<div igxDrag [dragChannel]="['Insects', 'Land']"> Ant </div>

<div igxDrop [dropChannel]="['Mammals']"> Mammals </div>
<div igxDrop [dropChannel]="['Insects']"> Insects </div>
<div igxDrop [dropChannel]="['Land']"> Land </div>
html

    Drag e-mails on the right into the folders on the left.

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    Advanced Configuration

    Since both igxDrag and igxDrop combined can be used in many different and complex application scenarios, the following example demonstrates how they can be used in an Kanban board.

    The user could reorder the cards in each column. It is done by setting each card also a drop area, so we can detect when another card has entered its area and switch them around at runtime, to provide better user experience.

    It won't be Kanban board without also the ability to switch cards between columns. A card can be directly moved from one column to another column at a specific position. It is achieved here with a dummy object, so it would create a visual area where the card will be position if released. The dummy object is removed once the dragging of a card ends or exits another column.

    Drag items around the kanban board.

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    API

    References

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