使用C#编写BHO实现残障人群上网冲浪无障碍

原文发表于作者博客 http://www.nod6.net——以c#和Objective－C为主题的网站。


先看一个效果图：



位于下方的工具栏即是我们编写的BHO组件。它本质上是一个DLL，是由IE浏览器加载的，它的生命周期=浏览器进程的生命周期。更多关于BHO的信息，请大家自行Google。IE8是多进程浏览器，因此没打开一个选项卡，或者每打开一个新的窗口就会启动这样一个BHO组件。那么，IE是如何知道要加载哪些BHO呢？答案是：注册表。注册表是Windows最重要的配置数据库，BHO的配置也不例外，它位于注册表的如下位置：
Software/Microsoft/Windows/CurrentVersion/Explorer/Browser Helper Objects
因此，我们只需要编写一个bat文件注册即可：
C:/Windows/Microsoft.NET/Framework/v4.0.30319/regasm /codebase “bin/Debug/MyBHO.dll”
那么，接下来我们关注下BHO本身，如何编写一个BHO组件呢？很简单，只需4步即可搞定：
1、编写一个接口：
using System;
using System.Runtime.InteropServices;
namespace MyBHO
{
[
ComVisible(true),
InterfaceType(ComInterfaceType.InterfaceIsIUnknown),
Guid("FC4801A3-2BA9-11CF-A229-00AA003D7352")
]
public interface IObjectWithSite
{
[PreserveSig]
int SetSite([MarshalAs(UnmanagedType.IUnknown)]Object site);
[PreserveSig]
int GetSite(ref Guid guid, out IntPtr ppvSite);
}
}
2、实现该接口
[
ComVisible(true),
Guid("B4BC397F-B34**A79-972F-1B4D6D81DA1E"),
ClassInterface(ClassInterfaceType.None)
]
public class FirstBHO : IObjectWithSite
{
//...
}
3、生成证书，并将证书应用到该BHO项目
“C:/Program Files/Microsoft SDKs/Windows/v7.0A/bin/NETFX 4.0 Tools/sn” -k MyBHO.key
4、注册安装。

public int SetSite(object site)
{
if (site != null)
{
_webBrowser = site as WebBrowser;
if (_webBrowser != null)
{
DocumentComplete += _form.OnDocumentComplete;
_form.Gray += new EventHandler(_form_Gray);
_form.Reload += new EventHandler(_form_Reload);
_form.Restore += new EventHandler(_form_Restore);
_form.ZoomIn += new EventHandler(_form_ZoomIn);
_form.Zoom += new BHOForm.ZoomDelegate(_form_Zoom);
_form.Invert += new EventHandler(_form_Invert);
_form.XRay += new EventHandler(_form_XRay);
_form.Speech += new EventHandler(_form_Speech);
_form.StopSpeech += new EventHandler(_form_StopSpeech);
_webBrowser.DocumentComplete += new DWebBrowserEvents2_DocumentCompleteEventHandler(webBrowser_DocumentComplete);
}
}
else
{
if (_webBrowser != null)
{
_webBrowser.DocumentComplete += new DWebBrowserEvents2_DocumentCompleteEventHandler(webBrowser_DocumentComplete);
_webBrowser = null;
}
}
return 0;
}

其中第2步，需要重点关注SetSite方法，如下：

public int SetSite(object site)
{
if (site != null)
{
_webBrowser = site as WebBrowser;
if (_webBrowser != null)
{
DocumentComplete += _form.OnDocumentComplete;
_form.Gray += new EventHandler(_form_Gray);
_form.Reload += new EventHandler(_form_Reload);
_form.Restore += new EventHandler(_form_Restore);
_form.ZoomIn += new EventHandler(_form_ZoomIn);
_form.Zoom += new BHOForm.ZoomDelegate(_form_Zoom);
_form.Invert += new EventHandler(_form_Invert);
_form.XRay += new EventHandler(_form_XRay);
_form.Speech += new EventHandler(_form_Speech);
_form.StopSpeech += new EventHandler(_form_StopSpeech);
_webBrowser.DocumentComplete += new DWebBrowserEvents2_DocumentCompleteEventHandler(webBrowser_DocumentComplete);
}
}
else
{
if (_webBrowser != null)
{
_webBrowser.DocumentComplete += new DWebBrowserEvents2_DocumentCompleteEventHandler(webBrowser_DocumentComplete);
_webBrowser = null;
}
}
return 0;
}

至于界面，只需要新建一个Form就可以了，Form里没有任何业务逻辑（业务逻辑在FirstBHO中），只是一个人机接口而已。

至于Form和业务逻辑类FirstBHO的交互，是通过事件实现的。下面给出Form的代码：


using System;
using System.Windows.Forms;

namespace MyBHO
{
public partial class BHOForm : Form
{
public delegate void ZoomDelegate(object sender, ZoomEventArgs e);

public event EventHandler ZoomIn;
public event EventHandler Gray;
public event EventHandler Reload;
public event EventHandler Restore;
public event EventHandler Invert;
public event ZoomDelegate Zoom;
public event EventHandler XRay;
public event EventHandler Speech;
public event EventHandler StopSpeech;

public BHOForm()
{
InitializeComponent();
}

public void OnDocumentComplete(object sender, BHOEventArgs e)
{
if (!this.Visible)
{
this.Show();
}

this.textBox1.Text = e.Data as string;
}

private void button1_Click(object sender, EventArgs e)
{
ZoomIn(this, new EventArgs());
}

private void button2_Click(object sender, EventArgs e)
{
Gray(this, new EventArgs());
}

private void button3_Click(object sender, EventArgs e)
{
Reload(this, new EventArgs());
}

private void button4_Click(object sender, EventArgs e)
{
Restore(this, new EventArgs());
}

private void trackBar1_Scroll(object sender, EventArgs e)
{
Zoom(this, new ZoomEventArgs { ZoomValue = trackBar1.Value * 10 });
}

private void button5_Click(object sender, EventArgs e)
{
Invert(this, new EventArgs());
}

private void button6_Click(object sender, EventArgs e)
{
XRay(this, new EventArgs());
}

private void BHOForm_Load(object sender, EventArgs e)
{
Height = 80;
textBox1.Visible = false;
CalcWinLocation();
}

private void CalcWinLocation()
{
Top = Screen.PrimaryScreen.WorkingArea.Height - Height - 10;
Left = (Screen.PrimaryScreen.WorkingArea.Width - Width) / 2;
}


private void button7_Click(object sender, EventArgs e)
{
Speech(this, new EventArgs());
}

private void button8_Click(object sender, EventArgs e)
{
StopSpeech(this, new EventArgs());
}

private void BHOForm_MouseDoubleClick(object sender, MouseEventArgs e)
{
if (Height == 80)
{
Height = 300;
textBox1.Visible = true;
}
else if (Height == 300)
{
Height = 80;
textBox1.Visible = false;
}
CalcWinLocation();
}
}
}