Kotlin 在可为空的 WeakHashMap 迭代期间进行空检查

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。上面列举的例子。任何关于为什么会发生这种情况的想法都将不胜感激。谢谢！

澄清 ${backStackEntry?.localClassName} 有效，但我担心的是为什么 Android Studio 或构建逻辑没有显示 ${backStackEntry.localClassName} 的静态检查错误或编译错误。但是使用${entry.localClassName}，Android Studio 会将此标记为错误。

Answer 1

WeakHashMap<Activity, Int> 类型不提供有关其内容可空性的信息。

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

由于您明确指定了backStackEntry 可空性并且编译器仍然没有将backStackEntry 取消引用标记为错误，这一定是一个错误，您应该在youtrack.jetbrains.com/issues/KT 上报告它。