【发布时间】：2011-10-27 09:13:34
【问题描述】：
我有一个 ActiveX 组件，它扫描照片、将文件保存到客户端硬盘上的临时文件中并上传照片。
我有一个执行扫描部分的“TwainMan”实例，扫描完成后会触发“ImageScanned”事件。这是我的主要代码流程：
scanner = new TwainMan();
scanner.ImageScanned += new ImageScannedEventHandler(Scanner_ImageScanned);
将执行此操作的代码放入 EventHandler 委托方法“Scanner_ImageScanned”中：
private void Scanner_ImageScanned(object Sender, ImageScannedEventArgs e)
{
this.tempFileName = scanner.ToTempFile(e.Image);
MessageBox.Show("Scanned picture stored on the following location:\n" + this.tempFileName);
Upload(this.tempFileName); // works just fine
TriggerJSCallback(); // here is where the problem appears!
}
在 TriggerJSCallback 方法中，我只触发了我的 JS 回调：
private void TriggerJSCallback()
{
EventHandler DataPreparingFinished = this.DataPreparingFinished;
if (null != DataPreparingFinished) { DataPreparingFinished(this.tempFileName); }
}
请注意，如果我从主流程中触发 JSCallback“DataPreparingFinished”，则 JS Callback 侦听器（在我的 html 页面中定义）工作正常，但如果从“ Scanner_ImageScanned" 委托，因此不是来自主代码流。
我做错了什么？有人可以帮忙吗？
这是 html 页面中标记内的 JS 回调定义。
<script for="AXTwain" event="DataPreparingFinished(args)" language="javascript" type="text/javascript">
function AXTwain::DataPreparingFinished(args) {
alert("JS ALERT: SUCCESS!!! JS Callback working properly." + args);
// alert("The temp file is stored on: " + AXTwain.TempFileName);
}
</script>
如果我能显示更多代码可能会更好，这样你就会更好地了解我的问题到底是什么。
让我们从头开始...
下面是我的 HTML 页面，其中包括我的 ActiveXObject 实例化和 JS 回调/侦听器函数。
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>ActiveX TWAIN test page</title>
<object id="AXTwain" name="AXTwain" classid="clsid:d8ea830e-38b0-4f3b-8be4-39c417c27583"></object>
</head>
<body onload="myload();">
<h1 style="color:green;">AXTwain test page</h1>
<script type ="text/javascript">
function myload() {
if (AXTwain != null) {
AXTwain.AcquireImage();
}
}
</script>
<script for="AXTwain" event="DataPreparingFinished(args)" language="javascript" type="text/javascript">
// The "for" attribute should be set to the name of instance of your COM component.
// The "event" attribute should be set to the JavaScript function signature for the event.
// The name of the JavaScript function is the instance name of your COM component, followed
// by double colons, followed by the JavaScript signature of the event.
function AXTwain::DataPreparingFinished(args) {
alert("JS ALERT: SUCCESS!!! JS Callback working properly." + args);
}
</script>
</body>
</html>
下面是我的 ActiveX 包装类...
using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
namespace AXImageAcquisition
{
#region ActiveX attributes
[ProgId("AXImageAcquisition.AXTwain_01")]
[Guid("d8ea830e-38b0-4f3b-8be4-39c417c27583")]
[ComVisible(true)]
[ClassInterface(ClassInterfaceType.None)]
[ComSourceInterfaces(typeof(IComEvents))]
#endregion
public class AXTwain
{
#region Class Properties and Settings
private TwainMan scanner;
private String tempFileName;
public String TempFileName
{
get { return this.tempFileName; }
}
[ComVisible(false)]
public delegate void EventHandler(string args);
public event EventHandler DataPreparingFinished;
public bool imageScanned = false;
#endregion
#region Class Constructors
public AXTwain()
{}
#endregion
#region Class Methods
[ComVisible(true)]
public void AcquireImage()
{
this.DataPreparingFinished += new EventHandler(Delegate_DataPreparingFinished);
this.scanner = new TwainMan();
this.scanner.ImageScanned += new ImageScannedEventHandler(Scanner_ImageScanned);
TriggerJSCallback(); // HERE IN THE MAIN CODE FLOW THE MESSAGE GETS TO JS!!!
}
/// <summary>
/// Delegate that defines functionality for the ImageScanned event, defined in TwainMan class.
/// </summary>
/// <param name="Sender"></param>
/// <param name="e"></param>
public void Scanner_ImageScanned(object Sender, ImageScannedEventArgs e)
{
this.tempFileName = scanner.ToTempFile(e.Image);
Upload(this.tempFileName);
TriggerJSCallback(); // HERE (NOT IN THE MAIN CODE FLOW) THE MESSAGE NEVER GETS TO JS!!! WHYYYY? :(
}
/// <summary>
/// TODO!!!
/// </summary>
/// <param name="tempFileName"></param>
private void Upload(string tempFileName)
{
// TODO
}
/// <summary>
/// Test method for the DataPreparingFinished trigger.
/// </summary>
public void TriggerJSCallback()
{
EventHandler DataPreparingFinished = this.DataPreparingFinished;
if (null != DataPreparingFinished) DataPreparingFinished(this.tempFileName);
}
/// <summary>
/// Delegate that defines functionality for the DataPreparingFinished event, which is defined in IComEvents.
/// </summary>
/// <param name="msg">Arguments passing from C# to JS.</param>
void Delegate_DataPreparingFinished(string msg)
{
// MessageBox.Show("Delegate_DataPreparingFinished message! (C# code).\n Input message: " + msg);
}
#endregion
}
}
如果您需要更多代码，我还可以复制/粘贴其余代码，即 TwainMan 类及其依赖项。然而，所有这些都来自代码项目教程here。顺便说一句，感谢作者。
【问题讨论】：
标签： javascript c# callback activex dom-events