kotlin - 可空WeakHashMap迭代期间的Kotlin空检查

Question

// I know activity is not ideal here due to lack of equality guaranty; please ignore this part
private val mActivities: WeakHashMap<Activity, Int> = WeakHashMap()
....
mActivities.put(null, null)
mActivities.filter { (backStackEntry: Activity?) ->
    // Issue: this does not show any errors but fails at runtime
    Logger.warn("$TAG - Activity ${backStackEntry.localClassName}")
    val entry: Activity? = backStackEntry
    // Works as expected: this does show the error as expected
    Logger.warn("$TAG - Activity ${entry.localClassName}")
}

当我尝试遍历可能包含空值的WeakHashMap时，Kotlin空安全检查不起作用。上面列出的示例。关于为什么发生这种情况的任何想法将不胜感激。谢谢!

澄清 ${backStackEntry?.localClassName}有效，但是我担心的是为什么Android Studio或构建逻辑未显示 ${backStackEntry.localClassName}的静态检查错误或编译错误。但是，使用 ${entry.localClassName}，Android Studio会将其标记为错误。

Answer 1

WeakHashMap<Activity, Int>类型不提供有关其内容可为空的信息。

考虑将private val mActivities: WeakHashMap<Activity, Int> = WeakHashMap()替换为private val mActivities: MutableMap<Activity?, Int?> = WeakHashMap()。

由于您显式指定了backStackEntry可为空，并且编译器仍然没有将backStackEntry取消引用标记为错误，因此它一定是一个错误，应该在youtrack.jetbrains.com/issues/KT上进行报告。