javascript - 删除文件时无法检测到 chrome 扩展中的删除事件

Question

我正在构建一个 chrome 扩展，它允许用户拖放文件并将其保存到服务器。当我放下图像文件时，我从扩展程序中在页面中注入(inject)了一个 div 元素，浏览器在整个页面上显示图像。扩展中未检测到 drop 事件，但如果我有一个带有类型文件的输入元素，并且如果我将文件放在该元素上，则 change 事件是被检测到。

不确定如何检测扩展中的 drop 事件。感谢您的帮助。

contentScript.js 文件

//building the Dropzone Div
var dropdiv = $("<div>", {
  id    :"sforce-dz-dropZone",
  class : "sforce-dz-dropZonebg"
}).text('Add you\'re files here');

//injecting the drop div in the page
$("input[name=attachFile]").after(dropdiv);

//adding 'drop' event listener to the div.
//This is not getting logged at all.
$("#sforce-dz-dropZone").on('drop', function(e){
  e.preventDefault();
  e.stopPropagation();

  var files = e.target.files || e.dataTransfer.files;
  // process all File objects
  for (var i = 0, f; f = files[i]; i++) {
    console.log('the file name is '+ f.name);
  }

});

//Adding another event. click, just to see if the events are getting triggered.
//When clicked on the div the console is logging the below string.
$("#sforce-dz-dropZone").on('click',function(){
  console.log('clicked');
});

list 文件

{
  "name": "name",
  "version": "0.0.1",
  "manifest_version": 2,
  "description": "text",
  "author": "someone",
  "content_scripts": [
    {
      "matches" : ["https://*.mysite.com/*"],
       "js"     : ["jquery.js","contentScript.js"],
       "css"    : ["sforce-dz.css"]
    }
  ],
  "permissions": [
     "cookies",
     "unlimitedStorage"
  ]
}

Answer 1

这是处理拖放的真正令人困惑的部分。您可能希望像处理 click submit mouseOver 等操作一样只监听 drop 事件。但它不会工作，除非它也有一个 dragOver 事件。

“如果没有 dragOver 事件处理程序，则使用 dragOver 事件的默认事件处理程序，因此不会触发 drop 事件。” Answer Here

最简单的工作示例

/* events fired on the drop targets */
document.addEventListener("dragover", function( event ) {
  // prevent default to allow drop
  event.preventDefault();
});

document.addEventListener("drop", function( event ) {
  // prevent default action (open as link for some elements)
  event.preventDefault();
  console.log('dropped');
});

来自 HTML5Rocks 的工作示例

function handleFileSelect(evt) {
  evt.stopPropagation();
  evt.preventDefault();

  var files = evt.dataTransfer.files; // FileList object.

  // files is a FileList of File objects. List some properties.
  var output = [];
  for (var i = 0, f; f = files[i]; i++) {
    output.push('<li><strong>', escape(f.name), '</strong> (', f.type || 'n/a', ') - ',
                f.size, ' bytes, last modified: ',
                f.lastModifiedDate ? f.lastModifiedDate.toLocaleDateString() : 'n/a',
                '</li>');
  }
  document.getElementById('list').innerHTML = '<ul>' + output.join('') + '</ul>';
}

function handleDragOver(evt) {
  evt.stopPropagation();
  evt.preventDefault();
  evt.dataTransfer.dropEffect = 'copy'; // Explicitly show this is a copy.
}

// Setup the dnd listeners.
var dropZone = document.getElementById('drop_zone');
dropZone.addEventListener('dragover', handleDragOver, false);
dropZone.addEventListener('drop', handleFileSelect, false);