问题描述

我正在开发一个允许用户上传图像的应用程序(在 Node.js 中，与本例无关).使用带有输入 (type="file") 字段的表单可以正常工作.

I'm working on an application (in Node.js, which is irrelevant for this case) which allows the user to upload an image. It works fine using a form with an input (type="file") field.

但是，我想要的是能够使用 HTML5 拖放来上传图像.据我所知，可以将图像拖动到客户端，并且图像缩略图显示在 div 中.但是，我确实需要一些帮助才能使文件上传正常工作.

However, what I want is to be able to upload an image using HTML5 drag and drop instead. As far as i've come it's possible to drag an image to the client, and the image thumbnail is displayed in a div. However I really need some help with getting the file upload working.

问题是我想使用我现在正在使用的表单，并且(以某种方式)将文件的路径传递给输入字段，即流程将完全像现在一样工作，但不是选择一个通过浏览文件我想通过拖放将其附加到输入字段.

The thing is that I want to use the form that i'm using right now, and (somehow) pass the file's path to the input field, i.e. the flow will work exactly as it do now, but instead of choosing a file by browsing it I want to attach it to the input field by drag and drop.

在下面用于拖放的 js 代码中，拖放到客户端的文件存储在变量file"中，我可以使用file.name"、file.type"和file.size" 与之前使用表单的方式完全相同.但是，我无法访问文件路径"(file.path)，这使得无法访问文件服务器端进行上传，就像我之前那样.

In the js code below for drag and drop the file that was dragged to the client is stored in the variable "file", and i'm able to use "file.name", "file.type" and "file.size" exactly the same way as it works since before with the form. However, I can't access the files "path" (file.path) which makes it impossible to access the file server side for uploading the same way as I do it since before.

问题是，是否可以在文件被拖到客户端后将文件对象传递给输入字段，以便我可以点击提交"并上传文件?如果是这样，如何做到这一点?

The question is, is it possible to pass the file object to the input field after the file has been dragged to the client, so that I can click on "submit" and upload the file? If so, how could this be done?

提前致谢！

Dropbox 以及我用于文件上传的表单:

the dropbox as well as the form i'm using for file uploads:

<div id='upload'>
    <article>
        <div id='holder'>
            <p id='status'>File API and FileReader API not supported</p>
        </div>
    </article> 

    <form method='post' enctype='multipart/form-data' action='/file-upload'>
        <p>
            <input type='file' name='thumbnail'>
        </p>
        <p>
            <input type='submit'>
        </p>
    </form>
</div>

拖放代码:

uploadImage: function(){
    var holder = document.getElementById('holder'),
        state = document.getElementById('status');

    if (typeof window.FileReader === 'undefined') {
      state.className = 'fail';
    } else {
      state.className = 'success';
      state.innerHTML = 'File API & FileReader available';
    }

    holder.ondragover = function () { this.className = 'hover'; return false; };

    holder.ondragend = function () { this.className = ''; return false; };

    holder.ondrop = function (e) {
      this.className = '';
      e.preventDefault();

      var file = e.dataTransfer.files[0],
          reader = new FileReader();

      reader.onload = function (event) {
        holder.style.background = 'url(' + event.target.result + ') no-repeat center';
      };

      reader.readAsDataURL(file);

      return false;
    };
},

推荐答案

不能使用文件输入添加文件数据.不过，您可以做的(在其他技术中)是使用 base64(在使用 readAsDataURL 方法时，可以通过 reader.onload 事件作为 event.target.result 本地获得)) 编码数据并将其放入隐藏字段:

You cannot use the file input to add the file data. Nevertheless, what you can do (among other technics) is to use the base64 (natively available through the reader.onload event as event.target.result, when using readAsDataURL method) encoded data and put it into an hidden field :

html

<article>
    <div id='holder'>
        <p id='status'>File API and FileReader API not supported</p>
    </div>
</article> 

<form method='post' enctype='multipart/form-data' action='/file-upload'>
        <input type='file' name='thumbnail' />
        <input type='hidden' name='base64data' />
        <input type='submit' formenctype='application/x-www-form-urlencoded' />
</form>

js

reader = new FileReader();
reader.onload = function (event) {
    document.getElementById('base64data').setAttribute('value', event.target.result);
};
reader.readAsDataURL(file);

从服务器端，您将能够从文件中获取 base64 编码数据，只需对其进行解码并根据需要使用它.

From the server side you'll be able to get the base64 encoded data from the file, just decode it and use it as you want.

在提交表单时，您还可以更改enctype"属性(通过 formenctype 属性完成)并删除基本的 html 文件输入，因为数据将发布在文本字段中.

While submitting the form, you could also change the "enctype" attribute (done through the formenctype attribute) and remove the basic html file input, since the data will be post in a text field.

这篇关于从 HTML5 拖动和传递上传文件的路径拖放到输入字段的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持跟版网！