我还没有看到OpenLaszlo的任何好的文件上传组件。是否有文件上传组件的开源版本，它支持DHTML和Adobe AIR的拖放，以及两个运行时的预览功能？
从技术上讲，可以支持以下功能：
- 在所有桌面浏览器的DHTML中拖放文件上传 http://caniuse.com/#feat=dragndrop
- 在DHTML中预览Webkit浏览器和Firefox的图像，以及使用SWF运行时的所有浏览器的图像预览
- 对 Adobe Air 应用程序的拖放支持
也许有人有一个现有的组件，可以开源，并由社区维护或改进。
目前没有办法在OpenLaszlo应用程序的DHTML（又名HTML5）模式下进行文件上传，因为不幸的是，在该运行时无法将表单类型设置为enctype=multipart/form-data。
但是，您可以通过访问低级Flash API来使用OpenLaszlo应用程序的SWF（Flash）模式进行文件上传。目前尚不清楚如何做到这一点，所以我不久前自己写了一个类来做到这一点，它将在OpenLaszlo的（Flash）SWF8，SWF9和SWF10模式下工作。
我从未尝试过将OpenLaszlo应用程序编译为AIR但我相信Flash Upload也可能适用于这种情况。
这是我的班级，随意使用它：
（代码也可在此处使用：http://forum.openlaszlo.org/showthread.php?t=14566&highlight=fileReference ）
<library>
<switch>
<when property="$as3"><!-- SWF9/SWF10 -->
<!---
CLASS: <fileuploadhelper>
EXTENDS: <node> (lz.node)
DESCRIPTION:
This is the ActionScript3 (AS3) (SWF9/SWF8) version of the Flash file
upload object.
This allows users to upload files when compiled to a Flash Version that
uses ActionScript3 such as Flash 9 or Flash 10.
-->
<class name="fileuploadhelper" extends="node">
<!---
@param string uploadurl: (optional) default upload url to use if none
passed to this.upload()
-->
<attribute name="uploadurl" type="string" />
<!-- @keywords private -->
<!--- @param flash.net.FileReference file_reference: Flash file reference object -->
<attribute name="file_reference" type="expression" value="null" />
<!-- Imports Required for SWF9/SWF10 -->
<passthrough>
import flash.net.FileReference;
import flash.events.Event;
import flash.events.ProgressEvent;
import flash.events.IOErrorEvent;
import flash.events.SecurityErrorEvent;
import flash.net.URLRequest;
</passthrough>
<!-- *** METHODS *** -->
<handler name="oninit">
<![CDATA[
#passthrough {
this.file_reference = new FileReference();
file_reference.addEventListener(Event.SELECT,this.onSelect);
file_reference.addEventListener(Event.COMPLETE, this.onComplete);
file_reference.addEventListener(ProgressEvent.PROGRESS, this.progressHandler);
file_reference.addEventListener(IOErrorEvent.IO_ERROR, this.ioErrorHandler);
file_reference.addEventListener(SecurityErrorEvent.SECURITY_ERROR, this.securityErrorHandler);
}#
]]>
</handler>
<!---
Displays file browsing window and allows the user to select a file (or
cancel to close the window).
-->
<method name="browse">
<![CDATA[
#passthrough {
file_reference.browse();
}#
]]>
</method>
<!---
Return name of selected file
@returns string: the filename of the selected file
-->
<method name="getName">
return this.file_reference.name;
</method>
<!--- @keywords private -->
<!---
@param string submit_url: SWF9/10 #passthrough{...} requires URL to be
referenced in an attribute rather than a
locally defined OpenLaszlo variable or
a compilation error occurs.
-->
<attribute name="submit_url" type="string" />
<!---
Uploads the currently selected file.
@param string strURL: (optional) If defined upload the file to this
URL, otherwise upload to this.uploadurl
Note: required if this.uploadurl is not defined.
-->
<method name="upload" args="strURL = false">
<![CDATA[
if (strURL === false)
var strURL = this.uploadurl; // workaround for SWF9/10 compatibility
this.setAttribute('submit_url', strURL);
#passthrough {
var request:URLRequest = new URLRequest(submit_url);
file_reference.upload(request);
}#
]]>
</method>
<!-- * ABSTRACT handlers: Override to do something useful in instance * -->
<!--- @keywords abstract -->
<!---
ABSTRACT METHOD: OVERRIDE IN YOUR APPLICATION TO DO SOMETHING USEFUL
Called when user selects a file.
@param flash.events.Event ev: the select event
-->
<method name="onSelect" args="ev=null">
if ($debug) Debug.info('as3 (SWF9/10): fileuploadhelper.onSelect(): WARNING: This is an abstract method that should be overridden in your application to do something useful...');
</method>
<!--- @keywords abstract -->
<!---
ABSTRACT METHOD: OVERRIDE IN YOUR APPLICATION TO DO SOMETHING USEFUL
Called when progress event is captured.
@param {anything} objDummy: SWF8 requires file_reference object here, does nothing in SWF9/10
@param number bytesLoaded: the number of bytes of the file uploaded
@param number bytesTotal: the number of total bytes of the file to be uploaded
-->
<method name="onProgress" args="objDummy, bytesLoaded, bytesTotal">
if ($debug) Debug.info('as3 (SWF9/10): fileuploadhelper.onProgress(): WARNING: This is an abstract method that should be overridden in your application to do something useful...');
</method>
<!--- @keywords abstract -->
<!---
ABSTRACT METHOD: OVERRIDE IN YOUR APPLICATION TO DO SOMETHING USEFUL
Called when a file upload is complete.
@param flash.events.Event ev: the complete event
-->
<method name="onComplete" args="ev=null">
if ($debug) Debug.info('as3 (SWF9/10): fileuploadhelper.onComplete(): WARNING: This is an abstract method that should be overridden in your application to do something useful...');
</method>
<!--- @keywords abstract -->
<!---
ABSTRACT METHOD: OVERRIDE IN YOUR APPLICATION TO DO SOMETHING USEFUL
Called when the file upload fails.
@param flash.events.IOErrorEvent/flash.events.securityErrorEvent ev: the Flash Error Event
-->
<method name="onError" args="ev=null">
if ($debug) Debug.info('as3 (SWF9/10): fileuploadhelper.onError(): WARNING: This is an abstract method that should be overridden in your application to do something useful...');
</method>
<!-- * Internal Private Handlers * -->
<!--- @keywords private -->
<!---
This will pass the progress values to method this.onProgress()
@param flash.events.ProgressEvent ev: the Flash Progress Event
-->
<method name="progressHandler" args="ev=null">
this.onProgress(false, ev.bytesLoaded, ev.bytesTotal);
</method>
<!--- @keywords private -->
<!---
This will catch an ioError and call method this.onError()
@param flash.events.IOErrorEvent ev: the Flash Error Event
-->
<method name="ioErrorHandler" args="ev=null">
if ($debug) Debug.error('as3 (SWF9/10): fileuploadhelper.ioErrorHandler(): ERROR: ioError detected, could not upload file.');
this.onError(ev);
</method>
<!--- @keywords private -->
<!---
This will catch a securityError and call method this.onError()
@param flash.events.securityErrorEvent ev: the Flash Error Event
-->
<method name="securityErrorHandler" args="ev=null">
if ($debug) Debug.error('as3 (SWF9/10): fileuploadhelper.securityErrorHandler(): ERROR: securityError detected. Are you sure you are uploading to same domian as this application is being served from?');
this.onError(ev);
</method>
</class>
</when>
<when property="$as2"><!-- SWF8 -->
<!---
CLASS: <fileuploadhelper>
EXTENDS: <node> (lz.node)
DESCRIPTION:
This is the ActionScript2(AS2) (SWF8) version of the Flash file
upload object.
This allows users to upload files when compiled to a Flash Version that
uses ActionScript2 such as Flash 8
-->
<class name="fileuploadhelper" extends="node">
<!---
@param string uploadurl: (optional) default upload url to use if none
passed to this.upload()
-->
<attribute name="uploadurl" />
<!--- @keywords private -->
<!--- @param flash.net.FileReference file_reference: Flash file reference object -->
<attribute name="file_reference" />
<!-- *** METHODS *** -->
<handler name="oninit" args="invoker">
fr = new flash.net.FileReference();
this.setAttribute('file_reference', fr);
fr.addListener(invoker);
</handler>
<!-- *** METHODS *** -->
<!---
Displays file browsing window and allows the user to select a file (or
cancel to close the window).
-->
<method name="browse">
this.file_reference.browse();
</method>
<!---
Return name of selected file
@returns string: the filename of the selected file
-->
<method name="getName">
return this.file_reference.name;
</method>
<!---
Uploads the currently selected file.
@param string strURL: (optional) If defined upload the file to this
URL, otherwise upload to this.uploadurl
Note: required if this.uploadurl is not defined.
-->
<method name="upload" args="strURL">
if (strURL == null)
var strURL = this.uploadurl;
this.file_reference.upload(strURL);
</method>
<!-- * ABSTRACT HANDLERS * -->
<!--- @keywords abstract -->
<!---
ABSTRACT METHOD: OVERRIDE IN YOUR APPLICATION TO DO SOMETHING USEFUL
Called when user selects a file.
@param flash.events.Event ev: the select event
-->
<method name="onSelect" args="ev=null">
if ($debug) Debug.info('as3 (SWF9/10): fileuploadhelper.onSelect(): WARNING: This is an abstract method that should be overridden in your application to do something useful...');
</method>
<!--- @keywords abstract -->
<!---
ABSTRACT METHOD: OVERRIDE IN YOUR APPLICATION TO DO SOMETHING USEFUL
Called when progress event is captured.
@param flash.net.fileReference fr: file_reference object here
@param number bytesLoaded: the number of bytes of the file uploaded
@param number bytesTotal: the number of total bytes of the file to be uploaded
-->
<method name="onProgress" args="fr, bytesLoaded, bytesTotal">
if ($debug) Debug.info('as3 (SWF9/10): fileuploadhelper.onProgress(): WARNING: This is an abstract method that should be overridden in your application to do something useful...');
</method>
<!--- @keywords abstract -->
<!---
ABSTRACT METHOD: OVERRIDE IN YOUR APPLICATION TO DO SOMETHING USEFUL
Called when a file upload is complete.
@param flash.events.Event fr: the file_reference object
-->
<method name="onComplete" args="fr=null">
if ($debug) Debug.info('as3 (SWF9/10): fileuploadhelper.onComplete(): WARNING: This is an abstract method that should be overridden in your application to do something useful...');
</method>
<!--- @keywords abstract -->
<!---
ABSTRACT METHOD: OVERRIDE IN YOUR APPLICATION TO DO SOMETHING USEFUL
Called when the file upload fails.
@param flash.events.Event fr: the file_reference object
-->
<method name="onError" args="fr=null">
if ($debug) Debug.info('as3 (SWF9/10): fileuploadhelper.onError(): WARNING: This is an abstract method that should be overridden in your application to do something useful...');
</method>
</class>
</when>
</switch>
</library>
注意：这类似于HTML表单，您将文件上传发布到后端（可能是PHP，ASP等）上的接收脚本，该脚本将处理文件并将其存储在某个地方，网络上有很多关于如何做到这一点的教程，所以我没有包含它。至于拖放和预览，您必须自己在OpenLaszlo中编写一个相当复杂的应用程序才能执行此操作，我建议您查看教程和OpenLaszlo文档以学习如何执行此操作。