Cómo agregar arrastrar y soltar en React con React Beautiful DnD

Arrastrar y soltar es una técnica de interacción común que se agrega para permitir que las personas muevan intuitivamente cosas en una página. Esto podría ser reordenar una lista o incluso armar un rompecabezas.

¿Cómo podemos agregar esa interacción al crear una aplicación React con React Beautiful DnD?

• ¿Qué es arrastrar y soltar?
• ¿Qué es React Beautiful DnD?
• ¿Qué vamos a construir?
• Paso 0: Creando una nueva aplicación React.js
• Paso 1: Instalar React Beautiful DnD
• Paso 2: hacer que una lista se pueda arrastrar y soltar con React Beautiful DnD
• Paso 3: guardar el orden de la lista después de reordenar los elementos con React Beautiful DnD

¿Qué es arrastrar y soltar?

Arrastrar y soltar es más o menos lo que parece: es una interacción que permite a alguien hacer clic y arrastrar un elemento, luego soltarlo en otro lugar, lo que a menudo tiene un efecto secundario dentro de la aplicación.

Este efecto es bastante común en aplicaciones como listas de tareas pendientes o paneles de gestión de proyectos, donde debe priorizar y crear un orden sobre cómo se deben hacer las cosas.

Si bien arrastrar y soltar puede tener algunos casos de uso avanzados, nos ceñiremos a la funcionalidad de lista básica para nuestro tutorial.

¿Qué es React Beautiful DnD?

React Beautiful DnD es una biblioteca accesible de arrastrar y soltar de Atlassian. Si no conoces a Atlassian, son el equipo detrás de Jira. Si no está familiarizado con Jira, probablemente sea la herramienta ágil más grande de Internet en este momento.

Los objetivos del equipo eran proporcionar capacidades de arrastrar y soltar teniendo en cuenta la accesibilidad, además de mantener el rendimiento y la noche con una potente API.

¿Qué vamos a construir?

Comenzaremos con una lista simple y agregaremos la capacidad de arrastrar y soltar.

En este tutorial, no dedicaremos tiempo a crear la lista en sí. La lista que usaremos usa una lista desordenada estándar (

) y listar elementos (
• ) para crear una lista con un poco de CSS para que parezca tarjetas.

  Nos centraremos en agregar la capacidad de arrastrar y soltar para reorganizar la lista usando React Beautiful DnD.

  Paso 0: Creando una nueva aplicación React.js

  Para empezar, queremos una aplicación sencilla que incluya una lista de elementos. Este puede ser un proyecto existente o un proyecto nuevo usando su marco favorito como Create React App.

  Comencé con una nueva aplicación usando la aplicación Create React y agregué una lista simple de personajes de Final Space.

  

  Si desea comenzar desde el mismo lugar, puede clonar mi repositorio de demostración en esa rama y comenzar directamente conmigo.

  Este comando clonará la rama específica para comenzar:

  git clone --single-branch --branch part-0-starting-point [email protected]:colbyfayock/my-final-space-characters.git 

  De lo contrario, puede clonar el repositorio de forma normal y verificar la rama part-0-starting-point.

  Si desea seguir solo el código, primero creé una matriz de objetos:

  const finalSpaceCharacters = [ { id: 'gary', name: 'Gary Goodspeed', thumb: '/images/gary.png' }, ... 

  Y luego los recorro para crear mi lista:

  
        
  
          {finalSpaceCharacters.map(({id, name, thumb}) => { return ( 
         
   { name } 
   ); })} 
        

  ¡Sigue el compromiso!

  Paso 1: Instalar React Beautiful DnD

  El primer paso es instalar la biblioteca a través de npm.

  Dentro de su proyecto, ejecute lo siguiente:

  yarn add react-beautiful-dnd # or npm install react-beautiful-dnd --save 

  Esto agregará la biblioteca a nuestro proyecto y estaremos listos para usarla en nuestra aplicación.

  Paso 2: hacer que una lista se pueda arrastrar y soltar con React Beautiful DnD

  Con nuestra biblioteca instalada, podemos darle a nuestra lista la capacidad de arrastrar y soltar.

  Agregar contexto de arrastrar y soltar a nuestra aplicación

  En la parte superior del archivo, importe DragDropContextde la biblioteca con:

  import { DragDropContext } from 'react-beautiful-dnd'; 

  DragDropContext is going to give our app the ability to use the library. It works similarly to React’s Context API, where the library can now have access to the component tree.

  Note: If you plan on adding drag and drop to more than one list, you need to make sure that your DragDropContext wraps all of those items, like at the root of your application. You can not nest DragDropContext.

  We’ll want to wrap our list with DragDropContext:

  
       
  
         ... 
       

  At this point, nothing will have changed with the app and it should still load as it did before.

  Making our list a Droppable area

  Next, we want to create a Droppable area, meaning, this will allow us to provide a specific area where our items can be moved around inside.

  First, add Droppable to our import at the top of the file:

  import { DragDropContext, Droppable } from 'react-beautiful-dnd'; 

  For our purpose, we want our entire unordered list (

  ) to be our drop zone, so we’ll again want to wrap it with this component:

    {(provided) => ( 
         
  
           ... 
         
   )}   

  You’ll notice we wrapped it a bit differently this time though. First, we set a droppableId on our component. This allows the library to keep track of this specific instance between interactions.

  We’re also creating a function immediately inside of that component that passes in the provided argument.

  Note: This function can pass in two arguments including a snapshot argument, but we won’t be using it in this example.

  The provided argument include information and references to code that the library needs to work properly.

  To use it, on our list element, let’s add:

  This is going to create a reference (provided.innerRef) for the library to access the list element’s HTML element.  It also applies props to the element (provided.droppableProps) that allows the library to keep track of movements and positioning.

  Again, at this point, there won’t be any noticeable functionality.

  Making our items Draggable

  Now for the fun part!

  The final piece of making our list elements draggable and droppable is wrapping each list item with a component similar to what we just did with the entire list.

  We’ll be using the Draggable component, which again, similar to the Droppable component, will include a function where we’ll pass through props to our list item components.

  First, we need to import Draggable along with the rest of the components.

  import { DragDropContext, Droppable, Draggable } from 'react-beautiful-dnd'; 

  Next, inside of our loop, let’s wrap the returning list item with the component and it’s top level function.

  {finalSpaceCharacters.map(({id, name, thumb}) => { return (  {(provided) => ( 
   ... 
   )}  

  Because we now have a new top level component in our loop, let’s move the key prop from the list element to Draggable:

  {finalSpaceCharacters.map(({id, name, thumb}) => { return (  {(provided) => ( 
  

  We also need to set two addition props on , a draggableId and an index.

  We’ll want to add index as an argument into our map function and then include those props on our component:

  {finalSpaceCharacters.map(({id, name, thumb}, index) => { return (  

  Finally, we need to set some props on the list element itself.

  On our list element, add this ref and spread additional props from the provided argument:

   {(provided) => ( 
  

  Now, if we refresh our page, and hover over our list items, we can now drag them around!

  

  However, you’ll notice that when you start moving an item around, the bottom of the page appears to be a little messed up. There’s some overflow issues with our list items and our footer.

  You’ll also notice that in the developer console, React Beautiful DnD is giving us a warning message that we’re missing something called a placeholder.

  

  Adding a placeholder from React Beautiful DnD

  Part of React Beautiful DnD’s requirements is that we additionally include a placeholder item.

  This is something that they provide out of the box, but this is used to fill up the space that the item we’re dragging previously took.

  To add that, we want to include provided.placeholder at the bottom of our Droppable top level list component, in our case at the bottom of the

  :

   {(provided) => ( 
          
  
            ... {provided.placeholder} 
          
   )}  

  And if we start dragging things around in our browser, we can see that our page flow doesn’t have issues and the content stays where it should!

  

  The last issue though, is when you move something around, it doesn’t stay, so how can we save the order of our items?

  Follow along with the commit!

  Step 3: Saving list order after reordering items with React Beautiful DnD

  When we move our items, they stay where they land for a split second. But after React Beautiful DnD finishes doing its work, our component tree will rerender.

  When the components rerender, our items go back to the same place that they were before, because we never saved that outside of DnD’s memory.

  To resolve this, DragDropContext takes in an onDragEnd prop that will allow us to fire a function after dragging has complete. That function passes in arguments that includes the new order of our items so that we can update our state for the next render cycle.

  Saving our list items in state

  First, let’s store our items in state so that we’ll have something to update between cycles.

  At the top of the file, add useState to the React import:

  import React, { useState } from 'react'; 

  Then, we’re going to create our state using our default list of items.

  Add the following to the top of our App component:

  const [characters, updateCharacters] = useState(finalSpaceCharacters); 

  Because we’ll be updating our new characters state to provide our list items and their order, we’ll now want to replace the array we’re mapping through to our new state:

  
         
  
           {characters(({id, name, thumb}, index) => { 
         

  And if we save and refresh our page, nothing should change!

  Updating state when dragging items

  Now that we have our state, we can update that state any time our list items are dragged.

  The DragDropContext component that we added to our page takes in a prop onDragEnd. Like it sounds, that will fire a function whenever someone stops dragging an item in the list.

  Let’s add a function handleOnDragEnd as our prop:

  Next, we need that function to actually exist.

  We can define a function under our state:

  function handleOnDragEnd(result) { } 

  Our function takes an argument called result.

  If we add console.log(result) to the function and move an item in our list, we can see that it includes details about what should be the updated state after our move action.

  

  Particularly, we want to use the index value in both the destination and source properties, which tell us the index of the item being moved and what the new index of that item should be in the array of items.

  So using that, let’s add the following to our function:

  const items = Array.from(characters); const [reorderedItem] = items.splice(result.source.index, 1); items.splice(result.destination.index, 0, reorderedItem); updateCharacters(items); 

  Here’s what we’re doing:

  • We create a new copy of our characters array
  • We use the source.index value to find our item from our new array and remove it using the splice method
  • That result is destructured, so we end up with a new object of reorderedItem that is our dragged item
  • We then use our destination.inddex to add that item back into the array, but at it’s new location, again using splice
  • Finally, we update our characters state using the updateCharacters function

  And now after saving our function, we can move our characters around, and they save their location!

  

  Preventing errors from dragging out of bounds

  One issue with our implementation, is if someone doesn’t drag the item exactly within our defined containers, we get an error.

  

  The issue is that when we drag it outside of the defined container, we don’t have a destination.

  To avoid this, we can simply add a statement above the code that moves our item around that checks if the destination exists, and if it doesn’t, exits out of the function:

  function handleOnDragEnd(result) { if (!result.destination) return; 

  And if we reload the page and try to drag our item out again, our item snaps back to the original location without an error!

  

  Follow along with the commit!

  What else can we do with React Beautiful DnD?

  Custom styles when dragging and dropping

  When moving items, DnD will provide a snapshot of the given state. With this information, we can apply custom styles so that when we’re moving our items, we can show an active state for the list, the item we’re moving, or both!

  //react-beautiful-dnd.netlify.app/?path=/story/single-vertical-list--basic

  Dragging between different lists

  If you’ve used Trello before or a tool like it, you should be familiar with the concept of different columns that you can drag cards between so that you can prioritize and organize your tasks and ideas.

  This library allows you to do the same thing, providing the ability to drag and drop items from one draggable area to another.

  //react-beautiful-dnd.netlify.app/?path=/story/multiple-vertical-lists--stress-test

  

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