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从 LiveData 仅调用一次 postValue 时多次触发观察者

[英]Observer is triggered multiple times when calling postValue only once from LiveData

原文 2020-12-09 08:26:30 4 1 android/ android-livedata/ android-lifecycle

I'm using an AndroidViewModel with a LiveData that is observed in a Fragment.我正在使用带有在片段中观察到的 LiveData 的 AndroidViewModel。

However, even though I'm using postValue from the LiveData, the observer registered in an activity triggers more than once.但是，即使我使用 LiveData 中的 postValue，在活动中注册的观察者也会多次触发。 I know it's a common problem on LiveData but I haven't found yet a concrete solution.我知道这是 LiveData 上的一个常见问题，但我还没有找到具体的解决方案。

Does somebody know why this happens?有人知道为什么会这样吗？

1 个解决方案

Note: u need to provide the code.注意：您需要提供代码。

Answer回答

multiple triggers Causes:多重触发原因：

[Default] onChange() method in the observer will be called when the fragment is created (u will receive the last value emitted before the fragment get destroyed) [默认] 观察者中的 onChange() 方法将在片段创建时被调用（你将收到片段被销毁之前发出的最后一个值）
Or, you are using livedata.observe(this,...), (if it's true you need to use livedata.observe(viewlifecycleowner,...)或者，您正在使用 livedata.observe(this,...)，（如果是真的，您需要使用 livedata.observe(viewlifecycleowner,...)

Resource: https://proandroiddev.com/5-common-mistakes-when-using-architecture-components-403e9899f4cb资源： https://proandroiddev.com/5-common-mistakes-when-using-architecture-components-403e9899f4cb

https://medium.com/androiddevelopers/livedata-with-snackbar-navigation-and-other-events-the-singleliveevent-case-ac2622673150 https://medium.com/androiddevelopers/livedata-with-snackbar-navigation-and-other-events-the-singleliveevent-case-ac2622673150

https://medium.com/androiddevelopers/viewmodels-and-livedata-patterns-antipatterns-21efaef74a54 https://medium.com/androiddevelopers/viewmodels-and-livedata-patterns-antipatterns-21efaef74a54