Android SavedStateHandle 不保存在 ViewModel 中 [英] Android SavedStateHandle doesn't save in ViewModel

问题描述

我有一个带有 SavedStateHandle 参数的 ViewModel.我正在像这样保存一个字符串:

 私人乐趣 saveString(str: String) {state.set(KEY_STRING, str)}

然后我强制关闭我的应用程序并重新启动它，并想像这样检索保存的字符串:

有趣的 getSavedString():字符串?{返回 state.get(KEY_String)}

然而，它总是返回 null.任何想法如何正确使用 SavedStateHandle?

解决方案

然后我强制关闭我的应用并重新启动它.."

我猜你完全杀死了应用 =)

重现saveState案例的方法之一:

1. 启用开发者模式并检查不要保留活动
2. 进程限制 ->无后台进程
3. 在后台向您发送应用程序(SavedStateHandle 将保存)
4. 从后台恢复应用程序或点击应用程序图标(SavedStateHandle 将恢复)

另一种最简单的方法:

1. 在后台向您发送应用
2. 点击终止 (Logcat)

3. 从后台恢复应用或点击应用图标

<块引用>

如果你想，你也应该使用 SavedStateViewModelFactory在 ViewModel

中接收 SavedStateHandle

I have a ViewModel which takes a SavedStateHandle parameter. I am saving a String in there like this:

    private fun saveString(str: String) {
        state.set(KEY_STRING, str)
    }

Then I force-close my app and relaunch it, and want to retrieve the saved string like this:

fun getSavedString(): String? {
        return state.get<String>(KEY_String)
    }

However, it always returns null. Any ideas how to use SavedStateHandle correctly?

解决方案

"Then I force-close my app and relaunch it.."

I guess you kill the app completely =)

One of the way for reproducing saveState case you need:

1. Enable developers mode and check Don't keep activities
2. Process limit -> No background processes
3. Send you app in background (SavedStateHandle will saved)
4. Restore app from background or tap on the icon of app (SavedStateHandle will restored)

Another the easiest way:

1. Send you app in background
2. Tap terminate (Logcat)

3. Restore app from background or tap on the icon of app

Also you should use SavedStateViewModelFactory if you want to receive SavedStateHandle in ViewModel

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