WebBrowser 中不显示 java小程序 Applet

网页中有一个 java小程序 （Applet）

用ie 或者 世界之窗 可以正常使用 这个页面 内容完整

使用 WebBrowser 打开以后就 WebBrowser java小程序的位置就会显示为 一个灰色的 矩形【本来是有内容的】

打开页面过程中 会提示错误 *****为空或不是对象

解决方法 增加环境变量JAVA_PLUGIN_WEBCONTROL_ENABLE = TRUE

说明：可以调用API实现

Environment.SetEnvironmentVariable(StrName, strValue, EnvironmentVariableTarget.Machine);

错误提示依然存在 但是能用了

网上也有说JAVA_PLUGIN_WEBCONTROL_ENABLE＝1即可解决！

转自：http://blog.163.com/xiaobingking@126/blog/static/322371372011016134892/

C# 实现环境变量（采用 Environment 类)

private void  setEnvi(String StrName, String strValue)
{
Environment.SetEnvironmentVariable(StrName, strValue, EnvironmentVariableTarget.Machine);
}

private void setPathWithVariable(String strVariable)
{
String strHome = "%" + strVariable + "%";
setPathAfter(strHome);
}
private void setPathAfter(String strHome)//此时不会刷新path，需重启后刷新
{
String pathList = Environment.GetEnvironmentVariable("PATH");
//检测是否以;结尾
if (pathList.Substring(pathList.Length - 1, 1) != ";")
{
Environment.SetEnvironmentVariable("PATH", pathList + ";");
pathList += ";";
}
string[] list = pathList.Split(';');
bool isPathExist = false;

foreach (string item in list)
{
if (item == strHome)
isPathExist = true;
}
if (!isPathExist)
{
Environment.SetEnvironmentVariable("PATH", pathList + strHome + ";", EnvironmentVariableTarget.Machine);
}
}

============ 更改注册表===========================

注意，采用此方式修改的环境变量其实是修改了注册表里的变量值，修改之后，系统环境变量并没有更新，因此需要重启计算机，不推荐使用

/article/7030090.html

class SysEnvironment
{
/// <summary>
///
/// 获取系统环境变量
///
/// </summary>
///
/// <param name="name"></param>
///
/// <returns></returns>
///
public static string GetSysEnvironmentByName(string name)
{
string result = string.Empty;
try
{
result = OpenSysEnvironment().GetValue(name).ToString();
//读取
}
catch (Exception)
{
return string.Empty;
}
return result;
}
/// <summary>
/// 打开系统环境变量注册表
/// </summary>
/// <returns>RegistryKey</returns>
private static RegistryKey OpenSysEnvironment()
{
RegistryKey regLocalMachine = Registry.LocalMachine;
RegistryKey regSYSTEM = regLocalMachine.OpenSubKey("SYSTEM", true);
//打开HKEY_LOCAL_MACHINE下的SYSTEM
RegistryKey regControlSet001 = regSYSTEM.OpenSubKey("ControlSet001", true);
//打开ControlSet001
RegistryKey regControl = regControlSet001.OpenSubKey("Control", true);
//打开Control
RegistryKey regManager = regControl.OpenSubKey("Session Manager", true);
//打开Control
RegistryKey regEnvironment = regManager.OpenSubKey("Environment", true);
return regEnvironment;
}

/// <summary>
/// /// 设置系统环境变量
/// /// </summary>
/// / <param name="name">变量名</param>
/// <param name="strValue">值</param>
public static void SetSysEnvironment(string name, string strValue)
{
OpenSysEnvironment().SetValue(name, strValue);
}

/// <summary>
/// /// 检测系统环境变量是否存在
/// /// </summary>
/// <param name="name">
/// </param>
/// /// <returns></returns>
public bool CheckSysEnvironmentExist(string name)
{
if (!string.IsNullOrEmpty(GetSysEnvironmentByName(name)))
return true;
else
return false;
}
/// <summary>
/// 添加到PATH环境变量（会检测路径是否存在，存在就不重复）
/// /// </summary>    /// <param name="strPath"></param>
public static void SetPathAfter(string strHome)
{
string pathlist ;
pathlist = GetSysEnvironmentByName("PATH");

//检测是否以;结尾
if (pathlist.Substring(pathlist.Length - 1, 1) != ";")
{
SetSysEnvironment("PATH", pathlist + ";");
pathlist = GetSysEnvironmentByName("PATH");
}
string[] list = pathlist.Split(';');
bool isPathExist = false;

foreach (string item in list)
{
if (item == strHome)
isPathExist = true;
}
if (!isPathExist)
{
SetSysEnvironment("PATH", pathlist +strHome+ ";");
}
}
public static void SetPathBefore(string strHome)
{
string pathlist;
pathlist = GetSysEnvironmentByName("PATH");
string[] list = pathlist.Split(';');
bool isPathExist = false;
foreach (string item in list)
{
if (item == strHome)
isPathExist = true;
}
if (!isPathExist)
{
SetSysEnvironment("PATH", strHome + ";" + pathlist);
}
}
public static void SetPath(string strHome)
{
string pathlist;
pathlist = GetSysEnvironmentByName("PATH");
string[] list = pathlist.Split(';');
bool isPathExist = false;
foreach (string item in list)
{
if (item == strHome)
isPathExist = true;
}
if (!isPathExist)
{
SetSysEnvironment("PATH", pathlist + strHome + ";" );
}
}

Kernel32.DLL内有SetEnvironmentVariable函数用于设置系统环境变量

C#调用要用DllImport，代码封装如下：

class SetSysEnvironmentVariable
{
[DllImport("Kernel32.DLL ", SetLastError = true)]
public static extern bool SetEnvironmentVariable(string lpName, string lpValue);
public static void SetPath(string pathValue)
{
string pathlist;
pathlist = SysEnvironment.GetSysEnvironmentByName("PATH");
string[] list = pathlist.Split(';');
bool isPathExist = false;
foreach (string item in list)
{
if (item == pathValue)
isPathExist = true;
}
if (!isPathExist)
{
SetEnvironmentVariable("PATH", pathlist + pathValue+";");
}
}
}

转自：/article/2492652.html