java通过jni接口向C++中传值问题

Question

JNI WARNING: instance jfieldID 0x62bb4ff0 not valid for class Ljava/lang/Class; (GetIntField)

in Lcom/xxxx/test/MyActivity;.cmdHUProtoclVersion:(Lcom/xxxx/test/MyActivity$MyVersion;)I (GetIntField)
出现如上的warnning，数值设置不正确，该如何解决？

Answer 1

你这样找类名称是找不到的。要找到类的具体路径，从jni所在的那一层级开始往下目录查找，应该是这样找类，
jclass objresults = env->FindClass("com/XXXX/XXXX/MyActivity/MyVersion");
然后jfieldID my_majorversion = env->GetFieldID(objresults,"majorVersion","I");

Answer 2

java代码

 public class MyActivity extends Activity {

    public class MyVersion
    {
        public int majorVersion;
        public int minorVersion;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        int i =carlifelibstarttest();
        Toast.makeText(this, "Hello world", 10).show();
        System.out.println("Hello world!");
        TextView mTextview = new TextView(this);
        mTextview.setText(stringFromJNI());
        int j=connectionSetup();
        long p = class_init();

        carLifeLibInit();
        disconnect();
        carLifeLibDestory();
        MyVersion myVersion=new MyVersion();
        myVersion.majorVersion=1;
        myVersion.minorVersion=2;
        System.out.println(String.format("myVersion.majorVersion=%d,myVersion.minorVersion=%d", myVersion.majorVersion,myVersion.minorVersion));
        cmdHUProtoclVersion(myVersion);
        System.out.println(String.format("myVersion.majorVersion=%d,myVersion.minorVersion=%d", myVersion.majorVersion,myVersion.minorVersion));
        setContentView(mTextview);

    }
    public native int cmdHUProtoclVersion(MyVersion myVersion);
    public native int carlifelibstarttest();
    public native String stringFromJNI();
    public native long class_init();
    public native int connectionSetup();
    public native int carLifeLibInit();
    public native void carLifeLibDestory();
    public native void disconnect();
    static{
        System.loadLibrary("carlifeJni");
    }

jni

 jint Java_com_xxxx_carlife_VehicleNative_cmdHUProtoclVersion(JNIEnv* env, jobject thiz,jobject myobject)
{
    if(!g_obj)
        g_obj = env->NewGlobalRef(thiz);
    S_HU_PROTOCOL_VERSION *my_version=(S_HU_PROTOCOL_VERSION *)malloc(sizeof(S_HU_PROTOCOL_VERSION));
    jclass clazz;
    jfieldID my_majorversion;
    jfieldID my_minorversion;

    clazz= env->GetObjectClass(myobject);  
    if(clazz==NULL)
    {
        D("GetObjectClass Failed!\n");
        return -1;
    }
    my_majorversion=env->GetFieldID(clazz,"majorVersion","I");
    if(my_majorversion==NULL)
    {
        D("Failed to get majorVersion filedID!\n");
        return -1;
    }
    my_minorversion=env->GetFieldID(clazz,"minorVersion","I");
    if(my_minorversion==NULL)
    {
        D("Failed to get minorVersion filedID!\n");
        return -1;
    }

    my_version->majorVersion=env->GetIntField(clazz,my_majorversion);
    my_version->minorVersion=env->GetIntField(clazz,my_minorversion);

    D("majorVersion = %d,minorVersion = %d\n",my_version->majorVersion,my_version->minorVersion);
    env->SetIntField(clazz,my_majorversion,11);
    env->SetIntField(clazz,my_minorversion,22);
    D("majorVersion = %d,minorVersion = %d\n",my_version->majorVersion,my_version->minorVersion);

    return CCarLifeLib::getInstance()->cmdHUProtoclVersion(my_version);
    }

签名

 {"cmdHUProtoclVersion","(Lcom/xxx/test/MyActivity$MyVersion;)I",(void*)Java_com_xxxx_carlife_VehicleNative_cmdHUProtoclVersion}

Answer 3

最后那个MyVersion这个类是目录里面的成员类，我不确定是否是继续通过“/”来找到，我自己做，是在MyActivity这个类层级新建一个.java文件，声明MyVersion这个类，就百分百可以找到，你这样的做法，只能尝试一下com/XXXX/XXXX/MyActivity/MyVersion
或com/XXXX/XXXX/MyActivity$MyVersion