在 Android 中使用静态变量 [英] Using static variables in Android

问题描述

在 android 中，是否推荐使用静态变量?例如，在 Java 中实现单例模式，我通常会这样做:

In android, are using static variables a recommended practice? E.g, implementing a Singleton pattern in Java, I usually do:

private static A the_instance;
public static A getInstance() {
    if (the_instance == null) {
       the_instance = new A();
    }
    return the_instance;
}

此外，Android JVM 何时会清除这些内容?

Also, when does this get cleaned up by the Android JVM?

推荐答案

static 字段作为一个整体附加到 Class 实例，而后者又附加到ClassLoader 加载类.当整个 ClassLoader 被回收时，the_instance 将被卸载.我 90% 确定当 Android 销毁应用时会发生这种情况(不是当它进入后台或暂停时，而是完全关闭时.)

static fields are attached to the Class instance as a whole, which is in turn attached to the ClassLoader which loaded the class. the_instance would be unloaded when the entire ClassLoader is reclaimed. I am 90% sure this happens when Android destroys the app (not when it goes into the background, or pauses, but is completely shut down.)

因此，只要您的应用运行，就可以将其视为存在.单身人士是个好主意吗?人们有不同的看法.我个人认为使用得当就好.我认为答案在 Android 上没有太大变化.内存使用本身不是问题；如果你需要在内存中加载一堆东西，那要么是一个问题，要么不是，不管你是否将数据封装在一个单例中.

So, think of it as living as long as your app runs. Is Singleton a good idea? People have different views. I think it's fine when used appropriately, myself. I don't think the answer changes much on Android. Memory usage isn't the issue per se; if you need to load a bunch of stuff in memory, that's either a problem or it isn't, regardless of whether you encapsulate the data in a Singleton.

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