Comment ajouter un glisser-déposer dans React avec React Beautiful DnD

Le glisser-déposer est une technique d'interaction courante ajoutée pour permettre aux utilisateurs de déplacer intuitivement des éléments sur une page. Cela peut être de réorganiser une liste ou même de créer un puzzle.

Comment pouvons-nous ajouter cette interaction lors de la création d'une application React avec React Beautiful DnD?

  • Qu'est-ce que le glisser-déposer?
  • Qu'est-ce que React Beautiful DnD?
  • Qu'allons-nous construire?
  • Étape 0: Création d'une nouvelle application React.js
  • Étape 1: Installation de React Beautiful DnD
  • Étape 2: Créer une liste déplaçable et déposable avec React Beautiful DnD
  • Étape 3: Enregistrer l'ordre de la liste après avoir réorganisé les éléments avec React Beautiful DnD

Qu'est-ce que le glisser-déposer?

Le glisser-déposer est à peu près ce à quoi cela ressemble - c'est une interaction permettant à quelqu'un de cliquer et de faire glisser un élément, puis de le déposer ailleurs, ce qui a souvent un effet secondaire dans l'application.

Cet effet est assez courant dans les applications comme les listes de tâches ou le tableau de bord de gestion de projet, où vous devez hiérarchiser et créer un ordre pour la façon dont les choses doivent être faites.

Bien que le glisser-déposer puisse avoir des cas d'utilisation avancés, nous nous en tiendrons aux fonctionnalités de liste de base pour notre procédure pas à pas.

Qu'est-ce que React Beautiful DnD?

React Beautiful DnD est une bibliothèque accessible par glisser-déposer d'Atlassian. Si vous ne connaissez pas Atlassian, c'est l'équipe derrière Jira. Si vous n'êtes pas familier avec Jira, c'est probablement le plus gros outil Agile sur Internet actuellement.

Les objectifs de l'équipe étaient de fournir des capacités de glisser-déposer en gardant à l'esprit l'accessibilité, en plus de le garder nocturne et performant avec une API puissante.

Qu'allons-nous construire?

Nous allons commencer par une liste simple et ajouter la possibilité de glisser-déposer.

Dans cette procédure pas à pas, nous ne passerons pas de temps à créer la liste elle-même. La liste que nous allons utiliser utilise une liste standard non ordonnée (

Original text


    ) et les éléments de liste (
  • ) pour créer une liste avec un peu de CSS pour la faire ressembler à des cartes.

    Nous allons nous concentrer sur l'ajout de la possibilité de glisser-déposer pour réorganiser la liste à l'aide de React Beautiful DnD.

    Étape 0: Création d'une nouvelle application React.js

    Pour commencer, nous voulons une application simple qui comprend une liste d'articles. Cela peut être un projet existant ou un tout nouveau projet utilisant votre framework préféré comme Create React App.

    J'ai commencé avec une nouvelle application utilisant l'application Create React et j'ai ajouté une simple liste de personnages Final Space.

    Si vous voulez commencer à partir du même endroit, vous pouvez cloner mon référentiel de démonstration dans cette branche et commencer avec moi.

    Cette commande clonera la branche spécifique pour commencer:

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

    Sinon, vous pouvez cloner le référentiel comme d'habitude et extraire la branche part-0-starting-point.

    Si vous souhaitez suivre uniquement le code, j'ai d'abord créé un tableau d'objets:

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

    Et puis je les parcoure en boucle pour créer ma liste:

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

    • ); })}

    Suivez le commit!

    Étape 1: Installation de React Beautiful DnD

    La première étape consiste à installer la bibliothèque via npm.

    À l'intérieur de votre projet, exécutez ce qui suit:

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

    Cela ajoutera la bibliothèque à notre projet et nous serons prêts à l'utiliser dans notre application.

    Étape 2: Créer une liste déplaçable et déposable avec React Beautiful DnD

    Avec notre bibliothèque installée, nous pouvons donner à notre liste la possibilité de glisser-déposer.

    Ajout d'un contexte de glisser-déposer à notre application

    En haut du fichier, importez DragDropContextdepuis la bibliothèque avec:

    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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