Chapter 14. Test Your Knowledge Answers

This appendix contains answers to all the Test Your Knowledge quizzes that appear in the chapters.

Chapter 2 - Designing Form Screens

1. When designing a form screen, what is the first thing you should consider?
   • The data you need from your user - this will determine what fields are required and will inform your other decisions
2. What is the standard spacing increment in Material design?
   • 8 Density Independent Pixels
3. The ConstraintLayout, ViewPager, and CardView are part of the support APIs. What does this mean?
   • Their bytecode must be included with your application if you use them
4. When building a new layout, your root widget should always be which of these?
   • The simplest widget that makes sense for your layout - other options may provide more power, but will consume more system resources

Chapter 3 - Taking Actions

1. What's the best way to implement event handlers?
   • There isn't one - you need to consider each case, and choose the most appropriate pattern
2. What are the conditions for any methods that changes the state of a user-interface widget?
   • They must be called from the main thread
3. Code running as part of an event handler should fulfill which of the following conditions?
   • Only interact with the user interface - anything else should be done on a worker thread
4. When requesting data from another Activity, the data is returned through which of these?
   • A callback on your Activity object

Chapter 4 - Composing User Interface

1. When developing a layout subclass, which of the following options is the best?
   • Avoiding assigning ID attributes to child widgets - the ID attributes can cause unexpected side-effects in the application
2. Which of these applies to the Bundle passed at an Activity in onCreate?
   • It is populated in the onSaveInstanceState method
3. When the data for an Adapter changes, which of the mentioned happens?
   • It should notify any attached listeners
4. Fragments and View classes should meet which of the following conditions?
   • They should have their data and state pushed into them from the Activity

Chapter 5 - Binding Data to Widgets

1. Android's data binding framework follows what sort of binding?
   • Model-View (unidirectional) binding
2. Data Bound Layouts have variables that must be which of the following?
   • Any Java Object
3. Which of the following features belongs to data binding expressions?
   • They are a special expression language
4. To trigger an update of a data-bound user interface, you must do which of these?
   • Make a change that the Binding object can observe

Chapter 6 - Storing and Retrieving Data

1. The Room API for Android provides which of the following?
   • A lightweight API on top of SQLite
2. Returning LiveData from a Room DAO requires that you do which of these?
   • You observe it for changes in order to retrieve data
3. Database queries that don't return LiveData should do what?
   • Be run on a worker thread
4. Writing an update method for Room requires which of the listed?
   • An @Update method taking an Entity object on an interface

Chapter 7 - Creating Overview Screens

1. An instance of RecyclerView will create one View instance for which of these?
   • Every item of data visible on the screen
2. When attaching an observer to LiveData, you need to do which of the following?
   • Provide a valid LifecycleOwner

3. Overview/Dashboard screens should have which of these features?
   • They should display an overview with the most important information first
4. The ViewHolder class is used by the RecyclerView to do what?
   • Improve the data binding performance
5. When using LiveData objects to reference data used by multiple Fragment objects, which of these is true?
   • The Fragment instances must share the same LiveData reference to see changes

Chapter 8 - Designing Material Layouts

1. Elevation should be used for which of the following?
   • To selectively highlight one item above a flat layout
2. CoordinatorLayout can be used to coordinate movement and size between which of these?
   • Any of its direct child widgets
3. To change elevation of a widget in a backward-compatible way, you need to do which of the mentioned?
   • Use the ViewCompat class
4. The GridLayout class should be used in which of the following conditions?
   • To lay out screens along grid lines

Chapter 9 - Navigating Effectively

1. When using bottom tabs for navigation, which of these is important?
   • The tabs are of roughly equal importance
2. Top tabs are preferred to bottom tabs in which of these situations?
   • When the user won't need to navigate as frequently
3. Fragments can be used for navigation in which of these cases?
   • Any time the user navigates within the application
4. When the user selects an item in a navigation drawer, which of these is true?
   • The drawer should be closed programmatically

Chapter 10 - Making Overviews Even Better

1. How many different view types can you use in a single RecyclerView instance?
   • Any number
2. When using a DiffUtil, which of the following applies to the data you are comparing?
   • It is exposed through a Callback
3. When adding dividers to a RecyclerView, you should do which of these?
   • Make them distinct items in the dataset

Chapter 11 - Polishing Your Design

1. When choosing a color scheme, it's important that the accent color has which of these features?
   • It is complementary to the primary color
2. Dynamically generating a palette should meet which of these conditions?
   • It should be done on a background thread
3. Which of these is to be kept in mind while animating layouts in your application?
   • They should not block or distract the user from achieving their goals
4. Custom styles can be used to define which of these?
   • Default values for any attribute in a layout resource file

Chapter 12 - Customizing Widgets and Layouts

1. When rendering specialized graphics for a custom widget, you need to do which of these?
   • Override the onDraw method
2. Where should you create instances of graphics primitives such as Drawable, Paint, and Path for rendering in onDraw?
   • Anywhere that doesn't affect onDrawdirectly

3. What are the two phases involved in the layout process?
   • Measurement and then layout
4. When painting a Drawable object, you need to do which of the following?
   • Pass it a valid Canvas object
5. To tell the platform that a widget needs to repaint itself (from the main thread), you use which of these?
   • View.invalidate()