使用C++(JNI)从Java对象读取整数字段

Question

我试图从C++访问Java类中的"int"字段; 其实我也试过其他类型.我可以调用方法OK.但不是访问字段.我得到随机垃圾值而不是我期待的.

这是我的Java代码:

private class MYView extends View {
    public MYView(Context context) { super(context);  five = 555; }
    public int five;
....
}

C++部分:

jobject view = (jobject) Env->CallObjectMethod(Obj, jfindViewById, 3);
ClassMYView = Env->GetObjectClass(view);
jfieldID f = Env->GetFieldID(ClassMYView, "five", "I");
int i = Env->GetIntField(ClassMYView, f); <-- error is here, class is not object!

这是我在C++代码执行后得到的

view = 0x40521b80 
ClassMYView = 0x40521a70 
f = 0x444727e4
i = 4390958 // supposed to be 555!

请有经验的人,我做错了什么？谢谢.

Answer 1

也许你想写

jobject obj = (jobject) Env->CallObjectMethod(Obj, jfindViewById, 3);
ClassMYView = Env->GetObjectClass(obj);
jfieldID f = Env->GetFieldID(ClassMYView, "five", "I");
int i = Env->GetIntField(obj, f);

编译器没有给出错误,因为基本上jobject和jclass是相同的类型.