Question

http://www.codeguru.com/cpp/w-p/win32/tutorials/article.php/c10849/Setting-a-System-Environment-Variable.htm

SendMessage（HWND_BROADCAST，WM_SETTINGCHANGE，0，（LPARAM）“环境”）;

JNA和windows xp：调用以通知环境已更改

见链接：twall.github.com/jna/3.5.1/javadoc /

见链接：twall.github.com/jna/3.5.1/javadoc/com/sun/jna/platform/win32/User32.html

PostMessage（WinDef.HWND hWnd，int msg，WinDef.WPARAM wParam，WinDef.LPARAM lParam）

此函数将消息放入与创建指定窗口的线程关联的消息队列中，然后返回而不等待线程处理消息。

import com.sun.jna.*;
import com.sun.jna.win32.*;
import com.sun.jna.platform.win32.*;
import com.sun.jna.ptr.*;

public class MainJNA {

public static void main (String [] args){

String  myString = "Environment";
Pointer myPointer = new Memory(myString.length()+1);
    myPointer.setString(0,myString);

Pointer HWND_BROADCAST = new Pointer(0xFFFF);

int           msg    = 0x001A; // WM_SETTINGCHANGE = WM_WININICHANGE = 0x001A
WinDef.HWND   hWnd   = new WinDef.HWND( HWND_BROADCAST );
WinDef.WPARAM wParam = new WinDef.WPARAM(0);
WinDef.LPARAM lParam = new WinDef.LPARAM( myPointer.getLong(0) );
// Exception in thread "main" java.lang.IllegalArgumentException:
// Argument value 0x6d6e6f7269766e45 exceeds native capacity (4 bytes)
// mask=0xffffffff00000000

User32 user32 = (User32) Native.loadLibrary(
"user32" , User32.class , W32APIOptions.DEFAULT_OPTIONS );
user32.PostMessage( hWnd , msg , wParam , lParam );

}

} // end of class MainJNA

如何将String参数“Environment”传递给user32.PostMessage ???

并且不要在线程“main”中获取异常java.lang.IllegalArgumentException：参数值0x6d6e6f7269766e45超出本机容量（4字节）mask = 0xffffffff00000000

THX

Answer 1

您收到该错误是因为您尝试将64位值（myPointer.getLong(0)）写入32位容器（LPARAM）。

您已经拥有LPARAM中myPointer所需的指针值;将指针“强制转换”为LPARAM的推荐方法是简单地声明PostMessage的版本，该版本采用适当类型的第四个参数，例如

void PostMessage(WinDef.HWND hWnd, int msg, WinDef.WPARAM wParam, Pointer lParam);
void PostMessage(WinDef.HWND hWnd, int msg, WinDef.WPARAM wParam, String lParam);

与在不同类型之间手动转换（即从String或Pointer到整数类型）相比，这是更好的，更安全类型。

JNA调用PostMessage~传递String“Environment”

1 个答案: