Android navArgs 清除背面

Question

使用它们后有没有办法清除 navArgs ？我有片段 A 用 navArgs 打开片段 B，然后我导航到片段 C 并且用户按回，所以片段 B 用相同的 navArgs 打开，我不想要那样。

有没有办法在没有 navArgs 的情况下导航回片段 B？

谢谢。

Answer 1

胡安霍提出的答案绝对有效。唯一需要注意的是，您不能使用navArgs属性委托来获取它们，因为它是wrapped的Lazy。相反，您只需浏览底层arguments捆绑包即可。

例如，在 FragmentB 中

// don't need to pull in the navArgs anymore
// val args: FragmentBArgs by navArgs()

override fun onResume() {
  when (FragmentBArgs.fromBundle(arguments!!).myArg) {
    "Something" -> doSomething()
  }
  // clear it after using it
  arguments!!.clear()
}

// 现在当我回到这个片段时它们被清除了

Answer 2

Calling arguments?.clear() is not sufficient. Reason for that is that the navArgs() delegate holds all arguments in a local cached variable. Moreover, this variabel is private:

(taken from NavArgsLazy.kt)

private var cached: Args? = null

override val value: Args
    get() {
        var args = cached
        if (args == null) {
            ...
            args = method.invoke(null, arguments) as Args
            cached = args
        }
        return args
    }

I also find this approach pretty stupid. My use-case is a deeplink that navigates the user to a specific menu item of the main screen in my app. Whenever the user comes back to this main screen (no matter wherefrom), the cached arguments are re-used and the user is forced to the deeplinked menu item again.

Since the cached field is private and I don't want to use reflections on this, the only way I see here is to not use navArgs in this case and get the arguments manually the old-school way. By doing so, we can then null them after they were used once:

val navArg = arguments?.get("yourArgument")
if (navArg != null) {
  soSomethingOnce(navArg)
  arguments?.clear()   
}

Answer 3

我认为当你的片段 B 将被销毁时你可以删除参数

getArguments().clear();您可以在 onDestroyView() 中或每当您想要清除片段中的参数时使用该方法。