如何在运行时检查子类是否是类的实例？ [英] How to check if a subclass is an instance of a class at runtime?

问题描述

在Android应用程序测试套件中，我有一个这样的类，其中 B 是一个视图：

In an android app test suite I have a class like this where B is a view:

public class A extends B {
... etc...
}

现在我有一个视图对象列表，其中可能包含 A 对象，但在这种情况下我只关心它们是子类还是实例 B 。我想做类似的事情：

now I have a list of view objects which may contain A objects but in this case I only care if they're subclasses or "instances of" B. I'd like to do something like:

ArrayList<View> viewList = getViews();
Iterator<View> iterator = viewList.iterator();
while (iterator.hasNext() && viewList != null) {
    View view = iterator.next();
    if (view.getClass().isInstance(B.class)) {
        // this is an instance of B
    }
}

问题是如果遇到 A 对象不评估为code> B 的实例。有没有办法 isSubclassOf 还是什么？

The problem is that when the if encounters an A object it doesn't evaluate to an "instance of B". Is there a way to do isSubclassOf or something?

推荐答案

你有仔细阅读此方法的API。有时候你很容易感到困惑。

You have to read the API carefully for this methods. Sometimes you can get confused very easily.

它是：

if (B.class.isInstance(view))

API说：确定指定的对象 （参数）与此类 （您调用方法的类对象）所代表的对象分配兼容

API says: Determines if the specified Object (the parameter) is assignment-compatible with the object represented by this Class (The class object you are calling the method at)

或：

if (B.class.isAssignableFrom(view.getClass()))

API说：确定此类所代表的类或接口类对象与指定的Class参数

API says: Determines if the class or interface represented by this Class object is either the same as, or is a superclass or superinterface of, the class or interface represented by the specified Class parameter

或（没有反思和推荐的）：

or (without reflection and the recommend one):

if (view instanceof B)

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