HTML5上传文件显示进度

下面我们使用Html 5的新特性file api实现上传文件，并显示上传文件进度百分比。意图是这样的，当选择文件时，显示当前文件信息。这里我们是结合Asp.net MVC做为服务端，您也可以是其它的服务端语言。让我们看面这个片断的HTML：

 

    @using (Html.BeginForm("Upload", "Home", FormMethod.Post, new { enctype = "multipart/form-data" , id="form1"}))

    {    

        <div class="row">

            <label for="file">

                Upload Image:</label>

            <input type="file" name="fileToUpload" id="fileToUpload"  multiple="multiple" onchange="fileSelected();" />

        </div>

        <div id="fileName">

        </div>

        <div id="fileSize">

        </div>

        <div id="fileType">

        </div> 

        <div class="row">

            <input type="button" onclick="uploadFile()" value="Upload Image" />

        </div>

        <div id="progressNumber">

        </div>

    }

相关的Javascript是这样的： 

        function fileSelected() {

            var file = document.getElementById('fileToUpload').files[0];

            if (file) {

                var fileSize = 0;

                if (file.size > 1024 * 1024)

                    fileSize = (Math.round(file.size * 100 / (1024 * 1024)) / 100).toString() + 'MB';

                else

                    fileSize = (Math.round(file.size * 100 / 1024) / 100).toString() + 'KB';

                document.getElementById('fileName').innerHTML = 'Name: ' + file.name;

                document.getElementById('fileSize').innerHTML = 'Size: ' + fileSize;

                document.getElementById('fileType').innerHTML = 'Type: ' + file.type;

            }

        }

        function uploadFile() {

            var fd = new FormData();

            fd.append("fileToUpload", document.getElementById('fileToUpload').files[0]);

            var xhr = new XMLHttpRequest();

            xhr.upload.addEventListener("progress", uploadProgress, false);

            xhr.addEventListener("load", uploadComplete, false);

            xhr.addEventListener("error", uploadFailed, false);

            xhr.addEventListener("abort", uploadCanceled, false);

            xhr.open("POST", "Home/Upload");

            xhr.send(fd);

        }

        function uploadProgress(evt) {

            if (evt.lengthComputable) {

                var percentComplete = Math.round(evt.loaded * 100 / evt.total);

                document.getElementById('progressNumber').innerHTML = percentComplete.toString() + '%';

            }

            else {

                document.getElementById('progressNumber').innerHTML = 'unable to compute';

            }

        }

        function uploadComplete(evt) {

            /* This event is raised when the server send back a response */

            alert(evt.target.responseText);

        }

        function uploadFailed(evt) {

            alert("There was an error attempting to upload the file.");

        }

        function uploadCanceled(evt) {

            alert("The upload has been canceled by the user or the browser dropped the connection.");

        }

上面是就原生的Javascript，在onchange事件执行fileSelected的function，在点击button执行了uploadFile的function，这里使用XMLHttpRequest实现ajax上传文件。 注意代码在Firefox 14 可以工作，IE 9目前不支持file api，可以参加这里。 服务端的代码很简单： 

 

    public class HomeController : Controller

    {

        public ActionResult Index()

        {

            return View();

        }

        /// <summary>

        /// Uploads the specified files.

        /// </summary>

        /// <param name="fileToUpload">The files.</param>

        /// <returns>ActionResult</returns>

        [HttpPost]

        public ActionResult Upload(HttpPostedFileBase[] fileToUpload)

        {

            foreach (HttpPostedFileBase file in fileToUpload)

            {

                string path = System.IO.Path.Combine(Server.MapPath("~/App_Data"), System.IO.Path.GetFileName(file.FileName));

                file.SaveAs(path);

            }

            ViewBag.Message = "File(s) uploaded successfully";

            return RedirectToAction("Index");

        }

    }