Kotlin Fundamentals: Architecture components quiz

1. To avoid losing data during a device configuration change, store app data in which of these options?

   ViewModel

   LiveData

   Fragment

   Activity

2. A ViewModel should never contain any references to fragments, activities, or views. True or false?

   True

   False

3. When is a ViewModel destroyed?

   When the associated UI controller is destroyed and recreated during a device-orientation change.

   When there's a configuration change.

   When the associated UI controller is finished (if it's an activity) or detached (if it's a fragment).

   When the callback onCleared() is called.

4. How do you encapsulate the LiveData stored in a ViewModel so that external objects can read data without being able to update it?

   Inside the ViewModel, change the data type of the property to be LiveData and make it private. Use a backing property to expose a read-only property of type MutableLiveData.

   Inside the ViewModel, change the data type of the property to be MutableLiveData and make it private. Use a backing property to expose a read-only property of type LiveData.

   Inside the UI controller, change the data type of the property to MutableLiveData. Use a backing property to expose a read-only property of type LiveData.

   Inside the ViewModel, change the data type of the property to LiveData.

5. LiveData updates a UI controller (such as a fragment) if the UI controller is in which of the following states?

   Resumed

   In the background

   Paused

   Stopped

6. In the LiveData observer pattern, what's the observable item (what is observed)?

   The observer method

   The data in a LiveData object instance

   The UI controller

   The ViewModel

7. Which of the following statements is NOT true about listener bindings?

   Listener bindings are binding expressions that run when an event happens.

   Listener bindings work with all versions of the Android Gradle plugin.

   Listener bindings are written as lambda expressions.

   Listener bindings are similar to method references, but they let you run arbitrary data-binding expressions.

8. Assume your app includes this string resource Hello %s. Which of the following is the correct syntax for formatting the string, using the data-binding expression?

   android:text= "@{@string/generic_name(user.name)}"

   android:text= "@{string/generic_name(user.name)}"

   android:text= "@{@generic_name(user.name)}"

   android:text= "@{@string/generic_name,user.name}"

9. When is a listener-binding expression evaluated and run?

   When the data held by the LiveData is changed

   When an activity is re-created by a configuration change

   When an event such as onClick() occurs

   When the activity goes into the background

10. The Transformations.map() method provides an easy way to perform data manipulations on the LiveData and returns ___.

    A ViewModel object

    A LiveData object

    A formatted String

    A RoomDatabase object

11. What are the parameters for the Transformations.map() method?

    A source LiveData and a function to be applied to the value stored in LiveData

    Only a source LiveData

    No parameters

    ViewModel and a function to be applied

12. The lambda function passed into the Transformations.map() method is executed in which thread?

    Main thread

    Background thread

    UI thread

    In a coroutine

error_outline An error occurred when grading the quiz. Please try again.