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: