关于ajax上传文件的流程 和选择图片立即显示

关键点:

1.制作一个表单..然后把上传字段附加到该表单中

2.制作一个框架..把表单的_target的属性指向该框架.

3.提交表单..

 

jQuery.extend({

    



    createUploadIframe: function(id, uri)

    {

            //create frame

            var frameId = 'jUploadFrame' + id;

            var iframeHtml = '<iframe id="' + frameId + '" name="' + frameId + '" style="position:absolute; top:-9999px; left:-9999px"';

            if(window.ActiveXObject)

            {

                if(typeof uri== 'boolean'){

                    iframeHtml += ' src="' + 'javascript:false' + '"';



                }

                else if(typeof uri== 'string'){

                    iframeHtml += ' src="' + uri + '"';



                }    

            }

            iframeHtml += ' />';

            jQuery(iframeHtml).appendTo(document.body);



            return jQuery('#' + frameId).get(0);            

    },

    createUploadForm: function(id, fileElementId, data)

    {

        //create form    

        var formId = 'jUploadForm' + id;

        var fileId = 'jUploadFile' + id;

        var form = jQuery('<form  action="" method="POST" name="' + formId + '" id="' + formId + '" enctype="multipart/form-data"></form>');    

        if(data)

        {

            for(var i in data)

            {

                jQuery('<input type="hidden" name="' + i + '" value="' + data[i] + '" />').appendTo(form);

            }            

        }        

        var oldElement = jQuery('#' + fileElementId);

        var newElement = jQuery(oldElement).clone();

        jQuery(oldElement).attr('id', fileId);

        jQuery(oldElement).before(newElement);

        jQuery(oldElement).appendTo(form);





        

        //set attributes

        jQuery(form).css('position', 'absolute');

        jQuery(form).css('top', '-1200px');

        jQuery(form).css('left', '-1200px');

        jQuery(form).appendTo('body');        

        return form;

    },



    ajaxFileUpload: function(s) {

        // TODO introduce global settings, allowing the client to modify them for all requests, not only timeout        

        s = jQuery.extend({}, jQuery.ajaxSettings, s);

        var id = new Date().getTime()        

        var form = jQuery.createUploadForm(id, s.fileElementId, (typeof(s.data)=='undefined'?false:s.data));

        var io = jQuery.createUploadIframe(id, s.secureuri);

        var frameId = 'jUploadFrame' + id;

        var formId = 'jUploadForm' + id;        

        // Watch for a new set of requests

        if ( s.global && ! jQuery.active++ )

        {

            jQuery.event.trigger( "ajaxStart" );

        }            

        var requestDone = false;

        // Create the request object

        var xml = {}   

        if ( s.global )

            jQuery.event.trigger("ajaxSend", [xml, s]);

        // Wait for a response to come back

        var uploadCallback = function(isTimeout)

        {            

            var io = document.getElementById(frameId);

            try 

            {                

                if(io.contentWindow)

                {

                     xml.responseText = io.contentWindow.document.body?io.contentWindow.document.body.innerHTML:null;

                     xml.responseXML = io.contentWindow.document.XMLDocument?io.contentWindow.document.XMLDocument:io.contentWindow.document;

                     

                }else if(io.contentDocument)

                {

                     xml.responseText = io.contentDocument.document.body?io.contentDocument.document.body.innerHTML:null;

                    xml.responseXML = io.contentDocument.document.XMLDocument?io.contentDocument.document.XMLDocument:io.contentDocument.document;

                }                        

            }catch(e)

            {

                jQuery.handleError(s, xml, null, e);

            }

            if ( xml || isTimeout == "timeout") 

            {                

                requestDone = true;

                var status;

                try {

                    status = isTimeout != "timeout" ? "success" : "error";

                    // Make sure that the request was successful or notmodified

                    if ( status != "error" )

                    {

                        // process the data (runs the xml through httpData regardless of callback)

                        var data = jQuery.uploadHttpData( xml, s.dataType );    

                        // If a local callback was specified, fire it and pass it the data

                        if ( s.success )

                            s.success( data, status );

    

                        // Fire the global callback

                        if( s.global )

                            jQuery.event.trigger( "ajaxSuccess", [xml, s] );

                    } else

                        jQuery.handleError(s, xml, status);

                } catch(e) 

                {

                    status = "error";

                    jQuery.handleError(s, xml, status, e);

                }



                // The request was completed

                if( s.global )

                    jQuery.event.trigger( "ajaxComplete", [xml, s] );



                // Handle the global AJAX counter

                if ( s.global && ! --jQuery.active )

                    jQuery.event.trigger( "ajaxStop" );



                // Process result

                if ( s.complete )

                    s.complete(xml, status);



                jQuery(io).unbind()



                setTimeout(function()

                                    {    try 

                                        {

                                            jQuery(io).remove();

                                            jQuery(form).remove();    

                                            

                                        } catch(e) 

                                        {

                                            jQuery.handleError(s, xml, null, e);

                                        }                                    



                                    }, 100)



                xml = null



            }

        }

        // Timeout checker

        if ( s.timeout > 0 ) 

        {

            setTimeout(function(){

                // Check to see if the request is still happening

                if( !requestDone ) uploadCallback( "timeout" );

            }, s.timeout);

        }

        try 

        {



            var form = jQuery('#' + formId);

            jQuery(form).attr('action', s.url);

            jQuery(form).attr('method', 'POST');

            jQuery(form).attr('target', frameId);

            if(form.encoding)

            {

                jQuery(form).attr('encoding', 'multipart/form-data');                  

            }

            else

            {    

                jQuery(form).attr('enctype', 'multipart/form-data');            

            }            

            jQuery(form).submit();



        } catch(e) 

        {            

            jQuery.handleError(s, xml, null, e);

        }

        

        jQuery('#' + frameId).load(uploadCallback    );

        return {abort: function () {}};    



    },



    uploadHttpData: function( r, type ) {

        var data = !type;

        data = type == "xml" || data ? r.responseXML : r.responseText;

        // If the type is "script", eval it in global context

        if ( type == "script" )

            jQuery.globalEval( data );

        // Get the JavaScript object, if JSON is used.

        if ( type == "json" )

            eval( "data = " + data );

        // evaluate scripts within html

        if ( type == "html" )

            jQuery("<div>").html(data).evalScripts();



        return data;

    }

})

 

 

很多人问：在上传图片文件时，在上传之前怎么进行无刷新预览呢？这里我把我所使用的方法写一下，包括了flash和视频文件，代码如下。

选择页面JS代码：
<script language="javascript">
function checkData()
{
   var fileName=document.getElementById("FileUp").value;
   if(fileName=="")
     return;
     //检查文件类型
   var exName=fileName.substr(fileName.lastIndexOf(".")+1).toUpperCase()
      if(exName=="JPG"||exName=="BMP"||exName=="GIF")
       {
          //document.getElementById("myimg").src=fileName;
          document.getElementById("previewImage").innerHTML='<img src=\''+fileName+'\' width=100 height=100 >';
       }
     else
       if(exName=="SWF")
        {
          document.getElementById("previewImage").innerHTML='<embed src=\''+fileName+'\' width=\'100\' height=\'100\' quality=\'high\' bgcolor=\'#f5f5f5\' ></embed>';
         }
     else
        if(exName=="WMV"||exName=="MPEG"||exName=="ASF"||exName=="AVI")
         {
            var strcode='<embed src=\''+fileName+'\' border=\'0\' width=\'100\' height=\'100\'  quality=\'high\' ';
            strcode+=' autoStart=\'1\' playCount=\'0\' enableContextMenu=\'0\' type=\'application/x-mplayer2\'></embed>';
            document.getElementById("previewImage").innerHTML=strcode;
         }
    else
       {
          alert("请选择正确的图片文件");
          document.getElementById("FileUp").value="";
        }
     }

</script>

HTML代码：

<table border="0" cellpadding="0" cellspacing="0" width="100%" height="100%" ID="Table1">
<tr>
<td width="255" height="100%" valign="middle">
<INPUT id="FileUp" style="WIDTH: 253px; HEIGHT: 22px" type="file" size="23" name="File1"
runat="server" onchange="checkData()"><br>
&nbsp;&nbsp;注：这里可以是图片（jpg或gif格式）,flash动画（swf）及视频文件（wmv,mpeg,asf,avi）。大小限定在1M以内。
</td>
<td>
<div id="previewImage">当前页预览</div>
</td>
</tr>
</table>