useDraggable

Arguments

interface UseDraggableArguments {
id: string;
attributes?: {
role?: string;
roleDescription?: string;
tabIndex?: number;
},
data?: Record<string, any>;
disabled?: boolean;
}

Identifier

The id argument is a string that should be a unique identifier, meaning there should be no other draggable elements that share that same identifier within a given DndContext provider.

If you're building a component that uses both the useDraggable and useDroppable hooks, they can both share the same identifier since draggable elements are stored in a different key-value store than droppable elements.

Data

The data argument is for advanced use-cases where you may need access to additional data about the draggable element in event handlers, modifiers or custom sensors.

For example, if you were building a sortable preset, you could use the data attribute to store the index of the draggable element within a sortable list to access it within a custom sensor.

const {setNodeRef} = useDraggable({
id: props.id,
data: {
index: props.index,
},
});

Another more advanced example where the data argument can be useful is create relationships between draggable nodes and droppable areas, for example, to specify which types of droppable nodes your draggable node can be dropped on:

import {DndContext, useDraggable, useDroppable} from '@dnd-kit/core';
function Droppable() {
const {setNodeRef} = useDroppable({
id: 'droppable',
data: {
type: 'type1',
},
});
/* ... */
}
function Draggable() {
const {attributes, listeners, setNodeRef, transform} = useDraggable({
id: 'draggable',
data: {
supports: ['type1', 'type2'],
},
});
/* ... */
}
function App() {
return (
<DndContext onDragEnd={handleDragEnd}>
/* ... */
</DndContext>
);
function handleDragEnd(event) {
const {active, over} = event;
if (over && active.data.current.supports.includes(over.data.current.type)) {
// do stuff
}
}
}

Disabled

Since hooks cannot be conditionally invoked, use the disabled argument and set it to true if you need to temporarily disable a draggable element.

Attributes

The default values for the attributes property are sensible defaults that should cover a wide range of use cases, but there is no one-size-fits-all solution.

You know your application best, and we encourage you to manually attach only the attributes that you think make sense in the context of your application rather than using them all without considering whether it makes sense to do so.

For example, if the HTML element you are attaching the useDraggable listeners to is already a native HTML button element, although it's harmless to do so, there's no need to add the role="button" attribute, since that is already the default role of button.

Role

The ARIA "role" attribute lets you explicitly define the role for an element, which communicates its purpose to assistive technologies.

The default value for the "role" attribute is "button".

If it makes sense in the context of what you are building, we recommend that you leverage the native HTML <button> element for draggable elements.

Role description

The roleDescription argument can be used to tailor the screen reader experience to your application. For example, if you're building a sortable list of products you'd want to set the roleDescription value to something like "sortable product".

Tab index

The tabindex attribute dictates the order in which focus moves throughout the document.

  • Natively interactive elements such as buttons, anchor tags and form controls have a default tabindex value of 0.

  • Custom elements that are intended to be interactive and receive keyboard focus need to have an explicitly assigned tabindex="0"(for example, div and li elements)

In other words, in order for your draggable elements to receive keyboard focus, they need to have the tabindex attribute set to 0 if they are not natively interactive elements (such as the HTML button element).

For this reason, the useDraggable hook sets the tabindex="0" attribute by default.

Properties

{
active: {
id: UniqueIdentifier;
node: React.MutableRefObject<HTMLElement>;
rect: ViewRect;
} | null;
attributes: {
role: string;
tabIndex: number;
'aria-roledescription': string;
'aria-describedby': string;
},
isDragging: boolean;
listeners: Record<SyntheticListenerName, Function> | undefined;
node: React.MutableRefObject<HTMLElement | null>;
over: {id: UniqueIdentifier} | null;
setNodeRef(HTMLElement | null): void;
transform: {x: number, y: number, scaleX: number, scaleY: number} | null;
}

Active

active

If there is currently an active draggable element within the DndContext provider where the useDraggable hook is used, the active property will be defined with the corresponding id, node and rect of that draggable element.

Otherwise, the active property will be set to null.

isDragging

If the draggable element that is currently being dragged is the current one where useDraggable is used, the isDragging property will be true. Otherwise the isDragging property will be false.

Internally, the isActive property just checks if the active.id === id.

Listeners

The useDraggable hook requires that you attach listeners to the DOM node that you would like to become the activator to start dragging.

While we could have attached these listeners manually to the node provided to setNodeRef, there are actually a number of key advantages to forcing the consumer to manually attach the listeners.

Flexibility

While many drag and drop libraries need to expose the concept of "drag handles", creating a drag handle with the useDraggable hook is as simple as manually attaching the listeners to a different DOM element than the one that is set as the draggable source DOM node:

import {useDraggable} from '@dnd-kit/core';
function Draggable() {
const {attributes, listeners, setNodeRef} = useDraggable({
id: 'unique-id',
});
return (
<div ref={setNodeRef}>
/* Some other content that does not activate dragging */
<button {...listeners} {...attributes}>Drag handle</button>
</div>
);
}

When attaching the listeners to a different element than the node that is draggable, make sure you also attach the attributes to the same node that has the listeners attached so that it is still accessible.

You can even have multiple drag handles if that makes sense in the context of your application:

import {useDraggable} from '@dnd-kit/core';
function Draggable() {
const {attributes, listeners, setNodeRef} = useDraggable({
id: 'unique-id',
});
return (
<div ref={setNodeRef}>
<button {...listeners} {...attributes}>Drag handle 1</button>
/* Some other content that does not activate dragging */
<button {...listeners} {...attributes}>Drag handle 2</button>
</div>
);
}

Performance

This strategy also means that we're able to use React synthetic events, which ultimately leads to improved performance over manually attaching event listeners to each individual node. Why? Because rather than having to attach individual event listeners for each draggable DOM node, React attaches a single event listener for every type of event we listen to on the document. Once click on one of the draggable nodes happens, React's listener on the document dispatches a SyntheticEvent back to the original handler.

Node

setNodeRef

In order for the useDraggable hook to function properly, it needs the setNodeRef property to be attached to the HTML element you intend on turning into a draggable element:

function Draggable(props) {
const {setNodeRef} = useDraggable({
id: props.id,
});
return (
<button ref={setNodeRef}>
{/* ... */}
</button>
);
}

Keep in mind that the ref should be assigned to the outer container that you want to become draggable, but this doesn't necessarily need to coincide with the container that the listeners are attached to.

node

A ref to the current node that is passed to setNodeRef

Over

over

If you'd like to change the appearance of the draggable element in response to it being dragged over a different droppable container, check whether the over value is defined.

If a draggable element is moved over a droppable area, the over property will be defined for all draggable elements, regardless of whether or not those draggable elements are active or not.

If you'd like to make changes to only the active draggable element in response to it being moved over a droppable area, check whether the isDragging property is true.

Transform

After a draggable item is picked up, the transform property will be populated with the translate coordinates you'll need to move the item on the screen.

The transform object adheres to the following shape:

{
x: number;
y: number;
scaleX: number;
scaleY: number;
}

The x and y coordinates represent the delta from the point of origin of your draggable element since it started being dragged.

The scaleX and scaleY properties represent the difference in scale between the element that is currently being dragged and the droppable it is currently over, which can be useful if the draggable item needs to be dynamically resized to the size of the droppable it is over.