架构组件

1. Which of the following are reasons to use a ViewModel?

   选择合适的多项回答。

   A ViewModel and its data can survive orientation changes in an Activity/Fragment.

   A ViewModel allows you to separate code that updates the UI from code that doesn’t need to rely on the UI or its lifecycle.

   A ViewModel prevents your data from updating the UI automatically.

2. A ViewModel is destroyed after which of the following ?

   always after onStop

   always after onDestroy

   after onDestroy, if it not a configuration change

3. True or False: You should execute time-consuming tasks and I/O requests in your Activity/Fragment.

   True

   False

4. Why should you initialize and store LiveData in your ViewModel instead of a UI Controller?

   Both the ViewModel and LiveData are lifecycle aware.

   To ensure that the LiveData isn’t destroyed when the UI Controller is destroyed.

   To hide or separate implementation details making your app more flexible.

   All of the above

5. Which of the following allows you to use observe for changes?

   a LiveData object

   any mutable object

   any property in a ViewModel

   any property in a ViewModel or LiveData object

6. True or False: It’s OK for a ViewModel to directly reference a View or LifecycleOwner class.

   True

   False

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