Question

我有这个本机函数，当我将设备连接到我的系统时，我在JNA中获得null值我认为我在使用JNA的LPVOID maping时遇到问题任何想法都将受到赞赏。

CP210x_GetProductString( DWORD DeviceNum,LPVOID DeviceString,DWORD Options)

DeviceNum - 需要产品说明字符串，序列号或完整路径的设备索引。
DeviceString - 类型CP210x_DEVICE_STRING的变量，返回以NULL结尾的序列号，设备描述或完整路径字符串。
Options - 确定DeviceString是否包含产品说明，序列号或完整路径字符串的标记

JNA代码：

public class Helloworld {

    public interface CLibrary extends Library{
        CLibrary INSTANCE = (CLibrary) Native.loadLibrary(
            (Platform.isWindows() ? "CP210xManufacturing.dll" : "c"),
            CLibrary.class);

        int CP210x_GetProductString(int dn,String [] ds,int op);
    }

    public static void main(String[] args) {
        int dn=0;
        String dsc = new String[100];
        if(CLibrary.INSTANCE.CP210x_GetProductString(dn, dsc,
               CP210x.CP210x_RETURN_SERIAL_NUMBER) == CP210x.CP210x_SUCCESS){
        {
            for(int i=0;i<dsc.length;i++)
                System.out.print(dsc[i]);
            }

        }
    }
}

Answer 1

不知道这是否有效，但是来自CP210x_GetProductString的this description我认为你必须将一个长度为256的byte []传递给函数（填充字符串的缓冲区）。

 int CP210x_GetProductString(int dn,byte[] ds,int op);

 //use it like this
 byte[] rawString = new byte[256];
 int dn = ...;
 int op = ...;
 CP210x_GetProductString(dn,rawString,op);
 //You might have to choose a different Charset here
 //since I don't know what encoding the string uses I used the default
 String product = new String(rawString,Charset.defaultCharset());

JNA与Native Code的通信

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