如何在运行时检查子类是否是类的实例？

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?

答

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)

如何在运行时检查子类是否是类的实例？

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