什么是'savedInstanceState'？ [英] What is 'savedInstanceState'?

问题描述

我是Android开发的新手，但我对OOP概念有一些了解。我试图从Java角度学习Android。

I am new to Android Development but I have some knowledge of OOP concepts. I am trying to learn Android from Java perspective.

据我所知，第9行的 onCreate（）内的 savedInstanceState 是Bundle的声明类。在第10行，我们从超类中调用 onCreate（）方法。

I understand that savedInstanceState inside onCreate() on line 9 is the declaration of Bundle class. On line 10 we are calling the onCreate() method from the super class.

这是什么我没有解释：在第10行，我们将 savedInstanceState 本身作为参数传递给 onCreate（）方法。这对我来说没有意义，因为我希望传递一个 Bundle 类型的对象，但是我们传递的引用不是Bundle类型的对象。方法。

Here is what I don't unterstand: On line 10 we pass savedInstanceState itself as a parameter to the onCreate() method. This doesn't make sense to me as I would expect to pass an object which is of the Bundle type, but instead of that we pass a reference not an object of type Bundle to the method.

推荐答案

savedInstanceState是对Bundle对象的引用，该对象被传递到每个Android Activity的onCreate方法中。

The savedInstanceState is a reference to a Bundle object that is passed into the onCreate method of every Android Activity.

onCreate（）期望以Bundle作为参数调用，因此我们传递savedInstanceState。

The onCreate() expects to be called with a Bundle as parameter so we pass savedInstanceState.

活动有在特殊情况下，使用此捆绑包中存储的数据将自身恢复到以前的状态的能力。如果没有可用的实例数据，则savedInstanceState将为null。

Activities have the ability, under special circumstances, to restore themselves to a previous state using the data stored in this bundle. If there is no available instance data, the savedInstanceState will be null.

例如，savedInstanceState在第一次启动Activity时始终为null，但如果在循环期间销毁Activity，则可能为非null，因为onCreate被调用每次活动开始或重新开始。

For example, the savedInstanceState will always be null the first time an Activity is started, but may be non-null if an Activity is destroyed during rotation, because onCreate is called each time activity starts or restarts.

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