JNA呼叫PostMessage的〜传递字符串 “环境”

Question

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

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

JNA和Windows XP：电话通知说，环境已经改变

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的（WinDef.HWND的HWND，INT味精，WinDef.WPARAM wParam中，WinDef.LPARAM LPARAM）

该函数将消息放入与创建指定wi的线程关联的消息队列中ndow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 

如何通过字符串参数 “环境” user32.PostMessage ???

，而不是获得线程异常 “主” java.lang.IllegalArgumentException异常：参数值0x6d6e6f7269766e45超过本机容量（4个字节）=面膜0xffffffff00000000

THX

Answer 1

你得到错误，因为您要将64位值（myPointer.getLong(0)）写入32位容器（LPARAM）。

您已经拥有LPARAM所需的指针值myPointer;将“指针”“投”到LPARAM的推荐方式是简单地声明PostMessage的版本，该版本采用适当类型的第四参数，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); 

这是优选的，更类型安全比不同类型之间进行手动转换（即，从String或Pointer为整数型）。