char* Get_Surface(JNIEnv *env, jclass cls, jobject param, int sdk_version){        // Java层        jfieldID surface = env->GetFieldID(cls, "mSurface", "Landroid/view/Surface;");        jobject surface_cls = env->GetObjectField(param, surface);        // Native层       jclass surface_class = env->FindClass("android/view/Surface");       jfieldID surface_native = env->GetFieldID(surface_class, "mSurface", "I"); //"I"指整型        // the JNI also supports other functions such as GetIntField and SetFloatField for accessing instance fields of primitive types.        return (char*)(Surface*)env->GetIntField(surface_cls, surface_native);}理解GetIntField(char*)(Surface*)env->GetIntField(surface_cls, surface_native);Once you have obtained the field ID, you can pass the object reference and the field ID to the appropriate instance field access function: jstr = (*env)->GetObjectField(env, obj, fid);