Add a button to an app Let's do a quick test! You must answer at least 7 questions correctly to pass this quiz.

 

1. Which of the following is an example of a class?

   Choose as many answers as you see fit.

   A Car class that has a make and model, and that can be driven

   Correct!

   A Flower class that has a scent

   Correct!

   A Puppy class that has breed, weight and age, and that can bark

   Correct!

   A ShoppingCart class that has a cart size and cart value, and that can hold items

   Correct!

   A Song class that has lyrics

   Correct!

   None of these are examples of a class.
2. Which of the following is a difference between a class and an instance?

   Choose as many answers as you see fit.

   You can think of a class as a blueprint and an instance as the actual “thing".

   Correct!

   A class is like architectural plans for a bridge, and the Golden Gate bridge an instance of those plans.

   Correct!

   A class is for defining categories of "things", while instances are for defining their properties.
   You can create multiple instances from a class, but you can't create classes from instances.

   Correct!

3. For each of the following types of information, select whether it should be part of a class or an instance.

   Each answer only matches one item.

   Information about properties shared by all "things" belonging to the class, such as number of sides, number of legs, or that it has a color.

                                             Class                            Instance                        

   Correct!

   The specifics about a property, such as the specific color of a “thing” that can have a color.

                                             Class                            Instance                        

   Correct!

4. True or false? Every MainActivity class in Android must have a main() function.
   True

   False

   Correct!

5. Which of the following is NOT a way for creating a comment in Kotlin?

   Choose as many answers as you see fit.

   Add // at the beginning of or inside a line and anything after that // is considered a comment.
   Put /* or /** to start a block comment, and end it with */.
   Use // to turn the rest of a function into a comment.

   Correct!

   Use /* to start a comment that is one line long.

   Correct!

6. Which of the following statements about a conditional statement is true?

   Choose as many answers as you see fit.

   Partially Correct.

   A conditional statement is a way for you to set up a condition and ensure that code following it is only executed if that condition is met.

   Correct!

   A conditional statement does not require any keywords.
   A conditional statement should only be used with integers as input.

   Incorrect.

   A conditional statement can be used within functions to return output based on conditions defined in that function.

   Correct!

7. What is a good reason for you to add comments to your code?
   To explain to yourself or others why the code is written a certain way.

   To structure code, like chapter headings in books.

   To point out some part of the code that is very important.

   To explain to other developers how to use your code for their own programs.

   All of the above

   Correct!

   None of the above
8. Which of the following are Kotlin data types?

   Choose as many answers as you see fit.

   IntRange

   Correct!

   Num
   Int

   Correct!

   Boolean (true or false)

   Correct!

9. Which of the following are valid keywords used in conditional statements in Kotlin?

   Choose as many answers as you see fit.

   if, else

   Correct!

   if, then, stop
   when

   Correct!

   repeat, finish

Results

You scored 8 out of 9. Congratulations! You have passed this quiz.

1. Which of the following is true about class inheritance?
   Class inheritance lets you reuse code and makes your program easier to maintain.

   Properties and functions of the parent class(es) are available to the child class.

   You can define additional properties and functions that are specific to subclasses.

   You can override parent class members in subclasses.

   All of the above

   Correct!

2. Which of the following are true about abstract classes?

   Choose as many answers as you see fit.

   They can be extended by subclasses and implementations can be provided for abstract members of the class.

   Correct!

   They have an implementation for all of their properties and functions.
   They may have abstract properties or abstract functions.

   Correct!

   They can be instantiated.
   They are not fully implemented and cannot be instantiated.

   Correct!

   They need to be marked with the open keyword to be extended.
3. Fill-in-the-blanks

   Enter one or more words to complete the sentence.

   The  is called when you create an instance of a class.

   Correct!

4. How do you mark a property to be used only inside its current class?
   Use the override keyword.

   Use the val keyword.

   Use the private keyword.

   Correct!

   Use the closed keyword.

   It is not possible to do this.
5. Select all answers that are true for this XML layout when displayed on the screen. (You can sketch this out on a piece of paper first, if that helps.)
   <androidx.constraintlayout.widget.ConstraintLayout
       android:layout_width="match_parent"
       android:layout_height="match_parent">
       <TextView
           android:id="@+id/textViewA"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="A"
           app:layout_constraintStart_toStartOf="parent"
           app:layout_constraintTop_toTopOf="parent" />
       <TextView
           android:id="@+id/textViewB"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="B"
           app:layout_constraintEnd_toEndOf="parent"
           app:layout_constraintTop_toTopOf="parent" />
   </androidx.constraintlayout.widget.ConstraintLayout>
   

   Choose as many answers as you see fit.

   TextView A appears vertically stacked on top of TextView B.
   The starting edge of TextView A is aligned to the starting edge of the parent view.

   Correct!

   The starting edge of TextView B is aligned to the starting edge of the parent view.
   TextView B is horizontally and vertically centered within the parent.
   The tops of TextView A and TextView B are aligned to top of the parent view.

   Correct!

   The width of TextView A matches the width of the parent ConstraintLayout.

Results

You scored 5 out of 5. Congratulations! You have passed this quiz.

2. Which line(s) of XML code will produce an error?
   1    <TextView
   2        android:layout_width="wrap_content"
   3        android:layout_height"wrap_content"
   4        android:padding="8dp"
   5        android:text="@string/title"
   6        android:textSize=18sp />
   

   Choose as many answers as you see fit.

   Line 1 - Missing closing tag > after <TextView.
   Line 3 - Missing = symbol after android:layout_height attribute.

   Correct!

   Line 4 - The android:padding attribute does not exist for a TextView.
   Line 5 - You should use @str/title to refer to a string resource.
   Line 6 - Missing quotations around the attribute value 18sp.

   Correct!

3. Which of the following is true about Gradle?

   Choose as many answers as you see fit.

   Gradle is an automated build system used by Android Studio to build your apps.

   Correct!

   Gradle handles installing your app on a device.

   Correct!

   Your app’s build.gradle file is written in XML.
   You can configure Android-specific options for your project in your app’s build.gradle file.

   Correct!

   The gradle configuration for your project cannot change after you initially create the project.
4. Which of the following statements about app icons are true?

   Choose as many answers as you see fit.

   It is sufficient to provide a single bitmap image of your app icon in your project to make it appear high quality on a range of Android devices.
   mdpi, hdpi, xhdpi, xxhdpi, and xxxhdpi are density qualifiers for resource directories to indicate that these are resources to be used on devices with a specific screen density.

   Correct!

   Adaptive icons are made up of a foreground and background layer, and an OEM mask will be applied on top of them.

   Correct!

   Vector drawables only work for a certain screen density and should not be scaled.
5. Which of the below steps are part of changing the color of your app theme?

   Choose as many answers as you see fit.

   Modify the themes.xml (night) file.

   Correct!

   Set the primary and secondary color theme attributes of your app theme.

   Correct!

   Define the colors used in your app as color resources in the colors.xml file.

   Correct!

   Set the background color of your app in the activity's layout file.
   Set the color attribute on all your UI components.
   Change the name of your theme to your preferred color.
6. Why use the Material Components for Android library?

   Choose as many answers as you see fit.

   It provides widgets that follow the Material Design guidelines such as text fields and switches.

   Correct!

   It makes your code compile faster.
   It provides default Material themes that you can use directly or extend and then customize.

   Correct!

   It automatically suggests ways for your app to look better.
   It helps you more quickly build beautiful user experiences.

1. Fill-in-the-blanks

   Enter one or more words to complete the sentence.

   Before running the below code, simpleList should be initialized as a  list.

   println(simpleList)
   simpleList.add(-5)
   simpleList.remove(4)
   println(simpleList)
   

   Correct!

2. Which of the following statements are valid?

   Choose as many answers as you see fit.

   Partially Correct.

   val list = listOf(1, 2, 5)

   Correct!

   val oddNumbers = mutableListOf("1", "9", "15")

   Correct!

   val listValues: MutableList<Boolean>

   Incorrect.

   val fruits = list("apple", "banana", "pear")
   val words: List<String> = listOf("jump", "run", "skip")

   Correct!

3. Why does a RecyclerView need an Adapter?
   To adapt data to display on a specific device type

   To create a new ViewGroup

   To adapt data from a data source into JSON

   To create new ViewHolders and bind data to them

   Correct!

4. Which of the following are advantages to using RecyclerView?

   Choose as many answers as you see fit.

   RecyclerView comes with built-in layout managers.

   Correct!

   RecyclerView lets you use packages to organize your code.
   RecyclerView helps save processing time, which can help scrolling through a list smoother.

   Correct!

   RecyclerView is designed to be efficient for lists by reusing views that have scrolled off the screen.

   Correct!

   RecyclerView automatically incorporates Material Design components.
5. Which of the following is true about packages?

   Choose as many answers as you see fit.

   You can use packages to organize your code.

   Correct!

   In order to use a class from another package, you have to explicitly import it in your code.

   Correct!

   The package name is usually structured from specific to general.
   It is good practice to use packages to group classes by functionality.

   Correct!

6. What should you do to ensure that the correct type of resource ID is passed in to a constructor?
   Use an Adapter to force the type.

   Only use a stringResourceId or imageResourceId.

   Use resource annotations.

   Correct!

   Use a naming convention to pass the ID in the form R.<type>.

   None of the above
7. Fill-in-the-blanks

   Enter one or more words to complete the sentence.

   In the below code,  should be written in the for loop, so that the output returned is the list of numbers 1 through 3, with each number printed on a new line.

1. Which of the following is false about collections and higher order functions in Kotlin?
   Lists, maps, and sets can all use higher order functions.

   Lists are unordered, while maps and sets are ordered data types.

   Correct!

   Like the elements in a set, the keys in a map must be unique. However, multiple keys can map to the same value.

   Higher order functions such as map and filter can take lambda functions as parameters.
2. Given the following code, what is the result of oneWordCities[1]?
   val cities = listOf("Jeddah", "Bengaluru", "Shenzhen", "Abu Dhabi", "Mountain View", "Tripoli", "Bengaluru", "Lima", "Mandalay", "Tripoli")
   val oneWordCities = cities.toSet().toList().filter { !it.contains(" ")}.sorted()
   

   Tripoli

   Abu Dhabi

   Jeddah

   Correct!

   Bengaluru
3. Fill-in-the-blanks

   Enter one or more words to complete the sentence.

   A(n)  is a piece of data passed between activities when launching an intent.

   Correct!

4. If you open an app, and then leave the app using the back button, in which order were the following activity lifecycle methods called?
   onStart(), onCreate(), onDestroy(), onStop()

   onDestroy(), onStart(), onCreate(), onStop()

   onCreate(), onStart(), onStop(), onDestroy()

   Correct!

   onStart(), onCreate(), onStop(), onDestroy()
5. Which activity lifecycle method would be called if a dialog appears onscreen, partially obscuring an activity?
   onPause() because the activity is still displayed, but no longer has focus.

   Correct!

   onStop() because the activity does not need to respond to user input while the dialog is onscreen.

   onResume() because the activity needed to respond to user input to display the dialog.

   onDestroy() because the activity does not need to exist so long as it doesn’t have focus.
6. Which of the following is true about the lifecycle of a single activity?

   Choose as many answers as you see fit.

   onStart() can be called multiple times, while onCreate() can only be called once.

   Correct!

   onStop() can be called multiple times, while onPause() can only be called once.
   onDestroy() is called when the app enters the background.
   onResume() is called when the activity gains focus.

   Correct!

7. Which of the following is false about intents?
   Both implicit and explicit intents allow your app to launch another activity.

   Explicit intents require you to specify the class of the activity you want to show.

   Intents are performed using the startActivity() method.

   An implicit intent always results in the system asking the user which app to open.

   Correct!

8. An activity contains the following code in onCreate(). What will happen when this code is executed, if the intent property is null?
   val message = intent.extras?.getString("message"
   ).toString()
   

   The app will crash because it attempted to access the extras property on a null object.

   Correct!

   The app will crash because it attempted to access a null object.

   The app will not crash because the extras property is accessed unsafely using ?.

   The app will not crash because the extras property is accessed safely using ?.
9. Which of the following tasks can be performed in onCreate()?

   Choose as many answers as you see fit.

   Partially Correct.

   Configuring views, such as setting the layout manager of a recycler view.

   Correct!

   Determining the items to be shown in the options menu.

   Incorrect.

   Setting the onClickListener for items in the options menu.
   Getting extras from the intent that launched the activity.

   Correct!

10. In which method should you handle what happens when a button in the app bar is pressed?
    onCreateOptionsMenu()

    openOptionsMenu()

    onOptionsItemSelected()

    Correct!

    onPrepareOptionsMenu()

Results

You scored 9 out of 10. Congratulations! You have passed this quiz.

1. True or False: You can use the same ViewModel for multiple Activities or Fragments to share data.
   True

   False

   Incorrect.

2. What is the correct way to access the shared view model using the Kotin property delegate approach?
   val viewModel: OrderViewModel by viewModels()

   val viewModel: OrderViewModel by activityViewModels()

   Correct!

   val viewModel: OrderViewModel by sharedViewModels()

   val viewModel: OrderViewModel by fragmentViewModels()
3. Fill-in-the-blanks

   Enter one or more words to complete the sentence.

   Use a LiveData  to return a different LiveData instance based on the value of another instance.

   Correct!

4. How can the apply function in Kotlin be used to configure an object?
   It can directly apply the object.

   It can apply a set of assignments to the object.

   Correct!

   It can apply new instances from the object.

   It is not recommended to use apply to configure an object.

5. 
   

6. Using a data binding layout expression, what’s the correct syntax for adding an attribute to the button in this layout in order to bind a click listener to it?
   <Button
       android:id="@+id/next_button"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:text="@string/next" />
   

   android:onClick="@{detailFragment.next()}"

   android:onClick="@{(Int) -> detailFragment()}"

   android:click="@{() -> detailFragment.next()}"

   android:onClick="@{() -> detailFragment.next()}"

   Correc

7. 1. True or False: onCreateView() is only called once for a fragment’s entire lifecycle.
      True

      False

      Correct!

   2. Which of the following is a benefit of using fragments?
      Navigation between fragments allows for more sophisticated user interface patterns, such as tab bars.

      Using multiple fragments within an activity allows for an adaptive layout across multiple screen sizes.

      The same fragments can be reused across multiple activities.

      All of the above

      Correct!

   3. In the fragment lifecycle, which of the following tasks should be performed in onViewCreated()?

      Choose as many answers as you see fit.

      Inflating the layout
      Binding view objects to properties in your fragment

      Correct!

      Configuring the options menu
      Setting properties of individual views, such as a recycler view’s adapter

      Correct!

   4. In the fragment lifecycle, which of the following tasks should be performed in onCreateView()?
      Inflating the layout

      Correct!

      Binding view objects to properties in your fragment

      Configuring the options menu

      Setting properties of individual views, such as a recycler view’s adapter
   5. Fill-in-the-blanks

      Enter one or more words to complete the sentence.

      The  method needs to be overridden in the host activity to ensure your app’s fragment-based navigation responds to the app’s "Up" button.

      Correct!

   6. Given the code for navigating between two fragments in a note-taking app, a list of books and a list of notes, which of the following is true about the navigation graph file?
      val action = BooksListFragmentsDirections.actionBooksListToNotesList(bookIndex = index)
      holder.view.findNavController().navigate(action)
      

      A: Both the books list and notes list are destinations.

      B: The books list fragment has an argument called bookIndex.

      C: There’s an action defined on the navigation graph that goes from the books list to the notes list.

      D: A, B, and C are true.

      E: Only A and C are true.

      Correct!

   Results

   You scored 6 out of 6. Congratulations! You have passed this quiz.

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

   Choose as many answers as you see fit.

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

   Correct!

   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.

   Correct!

   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

   Correct!

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

   False

   Correct!

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

   Correct!

5. observe allows you to do which of the following for changes?
   a LiveData object

   Correct!

   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

   Correct!

Results

You scored 6 out of 6. Congratulations! You have passed this quiz.

1. Which of the following is false about the @Query annotation?
   The @Query annotation is used with a method in the DAO.

   The @Query annotation corresponds to a SELECT query.

   The @Query annotation can pass arguments into a SQL statement by preceding their name with a colon.

   The @Query annotation can only be used with a suspend function.

   Correct!

2. Which of the following are true about the DAO?

   Choose as many answers as you see fit.

   DAO functions use annotations like @Insert and @Update that correspond to an operation on the database.

   Correct!

   DAO functions are typically called directly from a fragment.
   DAO functions can return a flow.

   Correct!

   Instances of DAO classes are referenced in the AppDatabase class.

   Correct!

3. Why do you need to use the synchronized() function when creating the database?

   Choose as many answers as you see fit.

   synchronized() is used to avoid race conditions.
   synchronized() ensures only one thread can enter the block of code at once.
   Doing so allows multiple copies of the database to be created.

   Correct!

   Calling synchronized() allows this code to be safely accessed from multiple threads at once.

   Correct!

4. Which of the following is false about the AppDatabase class?
   AppDatabase is an abstract class that inherits from RoomDatabase.

   The AppDatabase holds a reference to the view models.

   Correct!

   The @Database annotation specifies the entities (tables) in the database.

   The getDatabase() function can create a new database, pre-populated from a file.
5. The @Insert and @Delete annotations can be used without providing a SQL statement.
   True

   Correct!

   False
6. Which of the following is true about the ViewModel in an app using Room?

   Choose as many answers as you see fit.

   The ViewModel interacts with the DAO.

   Correct!

   The ViewModel updates the UI on the main thread.
   The ViewModel exposes data from the database to your app's UI.

   Correct!

   The ViewModel is held by a reference in the AppDatabase class.
7. Fill-in-the-blanks

   Enter one or more words to complete the sentence.

   To handle conflicts when inserting into a database, you can pass an , such as IGNORE, to the @Insert annotation.
8. The ViewModel factory is a class that inherits from ___ and is responsible for creating instances of the ViewModel class.
   ViewModelFactory

   Incorrect.

   ViewModelFactory.Provider

   ViewModelProvider.Factory

   ViewModelProvider
9. True or False: In a Room app, the Application class allows other objects to access the AppDatabase class.
   True

   Correct!

   False

Results

You scored 7 out of 9. Congratulations! You have passed this quiz.

1. Which of the following is true about WorkManager
   Tasks are typically chained, but not run in parallel.

   WorkManager is part of Android Jetpack and requires a Gradle dependency to use.

   Correct!

   WorkManager does not necessarily guarantee that a task will be executed.

   WorkRequest is the name of the class responsible for scheduling and running tasks
2. Which of the following would not require WorkManager?
   Performing a GET request to a web service.

   Correct!

   Long running tasks such as downloading large amounts of data

   Scheduling a task to repeat after a set interval.

   Doing something while the app is in the background.
3. A Worker represents a task to be scheduled by WorkManager while a WorkRequest contains the actual code to be executed.
   True

   False

   Correct!

4. Making execution dependent on device state such as storage space and battery life are examples of
   chaining

   best practices

   constraints

   Correct!

   canceling tasks
5. Fill-in-the-blanks

   Enter one or more words to complete the sentence.

   For a single task, you'd create a OneTimeWorkRequest, whereas for a task that needs to repeat after a given interval, you'd create a .
6. In a chain, the output of the last WorkRequest becomes the input for the next WorkRequest.
   True

   Correct!

   False
7. Fill-in-the-blanks

   Enter one or more words to complete the sentence.

   The () method is implemented by subclasses of the Worker class and defines the code to be executed by a WorkRequest.
8. Which of the following are true about unique work chains?

   Choose as many answers as you see fit.

   An ExistingWorkPolicy is required to determine what happens to an in-progress task (kept, replaced, etc.)

   Correct!

   Tags can be used to get the WorkInfo for the request.

   Correct!

   If no tag is specified, you can still ensure a task is unique by setting the WorkManager ID
   Unique work can be canceled using the cancelUniqueWork() method and providing the tag.

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