伴随对象是否在应用程序的生命周期中保留在内存中 [英] Do companion objects remain in memory for app's lifecycle

问题描述

在Kotlin中，您可以使用一个伴随对象创建一个单例:

In Kotlin, you can create a singleton using a companion object:

class MyClass {
   companion object {
        fun doSomething() {

        }
    }
}

根据Kotlin文档，它指出:

According to the Kotlin docs, it states:

请注意，即使伴随对象的成员看起来像 其他语言的静态成员，在运行时仍是实例 真实对象的成员...

Note that, even though the members of companion objects look like static members in other languages, at runtime those are still instance members of real objects...

https://kotlinlang.org/docs/reference/object-declarations.html

这是否意味着在伴侣对象中使用函数后，类的实例(MyClass)会在应用程序的整个生命周期中保留在内存中? Android Studio中有没有办法检查是否是这种情况?

Does this mean that after using a function in the companion object, the instance of the class (MyClass) remains in memory for the entire lifecycle of the app? Is there a way in Android Studio to check to see if this is the case?

推荐答案

类实例(MyClass)在应用程序的整个生命周期中都保留在内存中 ?

instance of the class (MyClass) remains in memory for the entire lifecycle of the app?

JVM中的伴侣对象

科特林

class MyClass {
   companion object {
        fun doSomething() {

        }
    }
}

在JVM中转换的MyClass(Kotlin)

public final class MyClass {
   public static final MyClass.Companion Companion = new MyClass.Companion(null);

   public static final class Companion {
      public final void doSomething() {
      }

      private Companion() {
      }

      public Companion() {
         this();
      }
   }
}

如上面的代码，companion object在JVM中被声明为Companion类，并且在MyClass类中被创建为static字段.因此，不会被gc收集.因此，对象(Companion)的内存在ProcessLifecycle期间保留. static final object在正常情况下不会释放.

As above code, companion object is declared as Companion class in JVM, and it's created as static field inside MyClass class. Thus, isn't collected by gc. So, the memory of object(Companion) is remained during the ProcessLifecycle. static final object isn't released in normal case.

最后，如果在应用程序中引用了MyClass.Companion实例，则该实例将不会被垃圾回收. (在通用的Classloader上).

In conclusion, if referred to MyClass.Companion instance in application, that instance will not be garbage collected. (on general Classloaders).

*如果未在应用程序中引用MyClass.Companion实例，则可以通过代码收缩功能将其删除.

*If not referred to MyClass.Companion instance in application, it may be removed by code shrinking feature.

Android Studio中是否有一种方法可以检查是否是这种情况?

Is there a way in Android Studio to check to see if this is the case?

您可以通过 android studio>分析器>堆转储查看.

• https://developer.android.com/topic/performance/memory-overview
• https://developer.android.com/studio/build/shrink-code

• https://developer.android.com/topic/performance/memory-overview
• https://developer.android.com/studio/build/shrink-code

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