从匿名内部类中获取封闭类对象作为函数参数 [英] get the enclosing class object from anonymous inner class as function parameter

问题描述

不确定我是否在问一个合理的问题。我知道每个内部类都保持对封闭类对象的引用。给定匿名内部类作为函数参数，我可以引用封闭类之外的封闭类对象吗？

Not sure if I am asking a sound question. I know every inner class keeps a reference to the enclosing class object. So can I reference the enclosing class object outside that enclosing class given the anonymous inner class as function parameter?

class A{
    public static void foo(Thread t) {
        //here, how to get the reference of the enclosing class object of "t", 
        //i.e. the object of class B. I know, somebody might have put in a 
        //non-inner class Thread. But how can I check if "t" is really from an 
        //anonymous inner class of class B and then do something here?
    }
}
class B{
    public void bar() {
        A.foo(
        new Thread() {
            public void run() {
                System.out.println("inside bar!");
            }
        });
    }
}

推荐答案

获取 t 的封闭类，尝试 t.getClass（）。getEnclosingClass（）。请注意，如果没有封闭类，这将返回 null 。

For getting the enclosing class of t try t.getClass().getEnclosingClass(). Note that this would return null if there was no enclosing class.

获取封闭类的正确实例是不那么容易，因为这将依赖于一些
未记录的实现细节（即这个$ 0 变量）。以下是一些更多信息：在Java中，当我不在内部类时，如何访问外部类？

Getting the correct instance of the enclosing class is not that easy, since this would rely on some undocumented implementation details (namely the this$0 variable). Here's some more information: In Java, how do I access the outer class when I'm not in the inner class?

编辑：我想再次强调这个$ 0 方法是未记录的，可能与编译器有关。因此，请不要依赖于生产或关键代码。

Edit: I'd like to reemphasize that the this$0 approach is undocumented and might be compiler dependent. Thus please don't rely on that in production or critical code.

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