Xamarin

Front 1

True/False?

Linear Layouts require a layout_width and layout_height to be set.

Back 1

True

Front 2

Which one is not deprecated?

Match Parent

Fill Parent

Back 2

Match Parent

Front 3

What is the preferred unit when laying out android stuff?

Back 3

density-independent pixel (dp)

Front 4

How many physical pixels (px) would a 100 dp button occupy on a 480dpi screen?

Back 4

160 dpi is the baseline (same as G1)

480/160 = 3

3 * 100 = 300

Front 5

How do you designate the main activity in an app?

Back 5

Use an attribute on the class

[Activity(MainLauncher = true)]

public class PiActivity : Activity

{

...

}

Front 6

How do you create an ID for a view in Android?

Back 6

in the layout file, specify @+id/ViewName

Front 7

In android, how do you get the ID of a view to use in code?

Back 7

var blah = FindViewById(Resource.Id.ViewName);

Front 8

T/F: Xamarin provides wrappers for all of Mono.NET library

Back 8

False - It provides wrappers for most types, but not the whole library.

Front 9

In the folder structure, where do you place the layout files?

Back 9

In the layout folder

Front 10

What are the 3 types of layouts?

Back 10

Linear, relative, and grid.

Front 11

which one of these is not used? Mono base class library, mono class library, mono runtime, or C# compiler?

Back 11

Mono class library

Front 12

In Xamarin.Android, what does the linker do?

Back 12

It removes unused IL code in the mono assemblies and your assemblies to give you a smaller package. If you are using dynamic code (eg members accessed via reflection) you should turn the linker off.

Front 13

Which items do you need to have installed to develop Xamarin.Androidapps?

a) JDK(JavaSDK)

b) Android SDK

c) Mono.NET

d) Alloftheabove

Back 13

D

Front 14

Xamarin.Android compiles your C# to Java bytecodes in order to execute iton the Android Runtime (ART)?

a) True

b) False

Back 14

false

Front 15

What base class do Activity classes inherit from?

Back 15

Context

Front 16

What method do you call to launch a new activity?

Back 16

base.StartActivity(intent);

Front 17

You can think of a Context as representing _______________?

a) Your app

b) The Android OS running your app

c) The other apps installed on the device

Back 17

B

Front 18

What is an explicit Intent?

a) An Intent that targets an Activity built-in to the Android OS

b) An Intent that targets an Activity in the same .apk

c) An Intent that exactly identifies the target Activity

Back 18

C

Front 19

What is a bundle?

Back 19

A collection of key/value pairs passed between Activities.

Front 20

T/F Objects must be serializable to be passed in a bundle.

Back 20

True

Front 21

What are the 2 ways to serialize complex objects to/from a bundle?

Back 21

IParcelable and ISerializable

Front 22

What are intent extras?

Back 22

That's where you put bundles

Front 23

How do you pass arguments to an Activity?

a) You can't pass them directly, you need to upload the data to your server and then download them in the target Activity

b) In a Bundle inside an Intent

c) Add a URL-style query string to the target Activity name

Back 23

b

Front 24

Which of the following can you pass between Activities?

a) Simple types like integers, strings, etc.

b) Serialized objects

c) Object references

Back 24

A and B

Front 25

What method do you used when you want to pass data back to a calling activity?

Back 25

StartActivityForResult(Intent intent, int requestCode);

Set the ResultCode before returning to the calling Activity.

Can add a bundle to the SetResult method.

Front 26

What is the name of the method that gets called on the parent activity after the child activity calls SetResult and then returns back to the parent?

Back 26

OnActivityResult

Front 27

What is an implicit intent?

Back 27

It describes what you want done without specifying which activity should do it.

Front 28

What is an intent action?

Back 28

It specifies the work you want done. eg dial the phone, send a message, display some info

Front 29

What is intent data?

Back 29

A single piece of data for use by the target activity. eg map coordinates, phone number (tel:[phone])

Front 30

What is the mime type?

Back 30

The MIME Type indicates the type of the Data you want the Intent tomanipulate, it helps Android determine which Activity to launch.

Insert a new contact vnd.android.cursor.dir/contact

Add a calendar event vnd.android.cursor.dir/event

Front 31

What is the category?

Back 31

A Category restricts the kind of Activity you would like to handle yourIntent.

eg Preferences, Tab, Openable

Front 32

You can add code to monitor network connections directly in a SharedProject or Portable Class Library (True or False)?

a) True

b) False

Back 32

False because it is done differently per platform.

Front 33

To determine if an iOS device is roaming, you need to:

a) Check the IsRoaming property on the ConnectivityManager

b) Subscribe to the ReachabilityChanged event

c) You cannot detect roaming conditions on iOS

Back 33

C

Front 34

You can obtain network information about an Android device using themethod call:

a) Android.GetNetworkInformation

b) ConnectivityManager.ActiveNetworkInfo

c) ConnectivityManager.GetNetworkType

Back 34

B

Front 35

Which of the following are safe http calls (do not modify data):

A. Options

B. Head

C. Post

D. Patch

Back 35

A, B

Front 36

Which of the following are idempotent (can be called multiple times with same data and produce same result on the server side.

A. Options

B. Put

C. Post

D. Patch

E. Delete

Back 36

A, B, E

Front 37

What HTTP verb should be used to update an existing record?

a) GET

b) POST

c) PUT

d) UPDATE

Back 37

c

Front 38

One advantage of REST is that many operations are cacheable

a) True

b) False

Back 38

A. All the "safe" operations are cacheable.

Front 39

Which of these choices would potentially be valid to retrieve a resourcewith an id of "1" and a type of "fruit"?

a) GET www.store.com/api/food/1

b) GET www.store.com/api/food/fruit?id=1

c) GET www.store.com/api/food/fruit

d) POST www.store.com/api/food

e) All of the above are possible

Back 39

A, B, C

Front 40

A UIView is responsible for:

a) Event publishing

b) Visualization

c) Managing subviews

d) All of the above

e) None of the above

Back 40

d

Front 41

Auto Layout _____________

a) Is only available in the Designer

b) Describes relationships between visual elements

c) Must be used and cannot be turned off

Back 41

b

Front 42

Spacing constraints are used to position a viewa) True b) False

Back 42

true

Front 43

Classes that will be instantiated by iOS need to have which attribute?

Back 43

[Register ("TodoListViewController")

Front 44

The .designer.cs file

a) Is for coding a view’s behavior

b) Is a representation of the storyboard in codec) All of the aboved) None of the above

Back 44

b

Front 45

What method do you call to show a ViewController?

Back 45

PresentViewController. First tell the Storyboard to instantiate it (InstantiateViewController("ControllerName"), then call PresentViewController.

Front 46

How do you go back to the previous view controller?

Back 46

call this.DismissViewController

Front 47

True/False. You can use PrepareForSegue to pass data to a target screen?

Back 47

True

Front 48

The UITableViewDelegate is used to ___________ a. handleconvertingrawdataintovisualcells

b. provideatype-safecallbacktotheTableView

c. handle events and notifications from the TableView

d. All of the above

Back 48

C

Front 49

You can implement the data source and delegate ________

a. as separate classes: UITableViewDataSource and UITableViewDelegate

b. as asingle class–UITableViewSource

c. by overriding methods on UITableViewController directly

d. All of the above

Back 49

d

Front 50

Which 2 methods must be implemented in UITableView?

Back 50

GetCell and RowsInSection

Front 51

Which protocol provides a mechanism for interacting with with a TableView?

Back 51

UITableViewDelegate

Front 52

Which method is called when a user taps a row?

Back 52

RowSelected

Front 53

The GetCell method is used to _____________

a) create sections in the table

b)return an int count of the total number of rows the table should display

c) return a UITableViewCell populated with data for the correspondingrow index passed to the method

Back 53

c

Front 54

Displaying hundreds, or even thousands of rows of data in a Table View requiresthe code to __________________ (select all that apply)

a)Register a reuseidentifier foreach unique celltype

b) use a customDictionary<>

c) always use DequeueReusableCell

d) set all the UITableViewCellsub-viewproperties in GetCell andrepopulate them in case of cell reuse

Back 54

A, C, D

Front 55

What method do you call on the Navigation controller to show a new screen?

Back 55

navController.PushViewController(newViewController, bool Animated)

Front 56

How do you programmatically go back to the previous screen?

Back 56

navController.PopViewController(animated true)

Front 57

How do you change the behavior or appearance of the navigation controller?

Back 57

Use the navigationItem property.

Front 58

How do you instantiate a ViewController that is defined in a Storyboard?

Back 58

UIViewController controller = ...;

var sb = controller.Storyboard; var newVC = sb.InstantiateViewController ("myViewController");controller.PushViewController (newVC, controller);

Front 59

Tabbar navigation is ideal for how many screens?

Back 59

3 to 5 of equal importance.

Front 60

How do you create a tabbar from code?

Back 60

instantiate a ViewController.

Create a TabBarItem for the ViewController and pass in an icon and text to display.

Set the TabBarItem property of the ViewController to the TabBarItem.

In the TabBarViewController, set the ViewControllers property to an array of the ViewControllers that you instantiated.

Front 61

How do you create a master/detail view?

Back 61

UISplitViewController

Front 62

UISplitView is limited to how many navigation levels?

Back 62

2

Front 63

Which method would you use to replace the Master view for aUISplitViewController?

a) PushViewController

b) PresentModalViewController

c) ShowViewController

Back 63

C

Front 64

A UISplitViewController can push multiple levels of navigationand acts exactly like a UINavigationController on an iPhone

a) True

b) False

Back 64

B

Front 65

To assign child pages to a UIPageViewController, we can ______(choose all that apply)

a) assigntheViewControllersproperty

b) assignthePageViewControllersproperty

c) calltheAddPagemethod

d) assignaUIPageViewDataSource

Back 65

A, D

Front 66

When using the designer, we can assign child pages to a Page ViewController using the PageViewSegue

a) True

b) False

Back 66

B

Front 67

What are iOS Backgrounding options?

Back 67

Finite - any code but limited

long-running only specific tasks not time limited

background transfers - data transfer, not limited

Front 68

Which iOS background technique should you use to transfer thecontents of a catalogue of a shopping app in order to support offlineusage? a) Finite-Length Task

b) Background Transfer

c) Long-Running Task

Back 68

B

Front 69

Which iOS background technique should you use to encrypt and storeuser settings when the app gets backgrounded?

a) Finite-Length Task

b) Background Download

c) Long-Running Task

Back 69

a

Front 70

Which iOS background technique should you use to track the device’scurrent location?

a) Finite-Length Task

b) Background Download

c) Long-Running Task

Back 70

c

Front 71

What methods are called when transitioning to/from background state?

Back 71

WillEnterForeGround and DidEnterBackground

Front 72

How long does DidEnterBackground get to return?

Back 72

Around 5 seconds. One way to extend time is to use a FiniteLengthTask

Front 73

Under which conditions must you end a finite length task?

Back 73

App moves to foreground, the task completes, or the task expires.

Front 74

The remaining time available for a Finite-Length Task to finish is always______.

a) 10 minutes

b) 3 minutes

c) different

d) available through UIApplication.BackgroundTimeRemainingproperty

Back 74

d

Front 75

Calling UIApplication.BeginBackgroundTask(OnDone) [select all that apply]

a) starts a thread and executes OnDone() asynchronously

b) signals the operating system that it should not suspend currently running threads when backgrounded

c) triggers OnDone() if the available time for background operations isabout to expire

Back 75

B, C

Front 76

How are the rows in a ListView created?

a) TheListView creates them using a DataTemplate

b) The ListView asks the Adapter for each row as needed

c) Rows are always strings so there is no need to create them

Back 76

B

Front 77

What is ArrayAdapter's key limitation?

a) Dataobjectsmustbeinanarrayb) The rows it builds do not support ItemClickevents

c) It can only populate one TextView

Back 77

c

Front 78

How does ArrayAdapter convert the code-behind data into a string?

a) Calls ToString

b) Serializestheobject to XML

c) Uses reflection to get the first string property in the object

Back 78

a

Front 79

ViewHolder must inherit from what class?

Back 79

Java.Lang.Obj

Front 80

What is the View Holder pattern?

Back 80

Used to hold strong references to your view instead of findViewByID.

When you create a ViewHolder class with cached version of the image, text, etc of the view and attach it to the Tag property of the View.

Front 81

Which ListView event is raised when the user clicks on a row?

a) Click

b) ItemClick

c) ItemSelected

Back 81

B

Front 82

What is inflation?

a) Populating a list with rows

b) Creating a Drawable from an Asset file

c) Loading code-behind data into the views of a row

d) Creating a view hierarchy from a layout file

Back 82

d

Front 83

If you implement the view-holder pattern correctly, how many times willyou use FindViewById to locate each view in a row's view hierarchy?

a) 0

b) 1

c) 2

Back 83

b

Front 84

To provide indexing, you implement ISectionIndexer on which class?

a) The ListView itself

b) Your custom Adapter

c) YourMainActivity

Back 84

B

Front 85

GetSectionForPosition maps indices from ____________

a) list position to section index

b) section index to list position

c) view position to listposition

Back 85

a

Front 86

What is a framelayout?

Back 86

Essentially it is a container that allows you to swap out the contents on the fly.

Front 87

Which term describes the common use of FrameLayout?

a) Placeholder

b) Root

c) Border

Back 87

a

Front 88

A Fragment is bigger than an Activity.

a) True

b) False

Back 88

False. A fragment is held inside an activity.

Front 89

What is a view pager?

Back 89

ViewPager is a layout manager that lets the user step forward and back through a sequences of pages

Front 90

ViewPager handles replacing your fragments (transactions, etc) for you automatically?

a) True

b) False

Back 90

True

Front 91

Activities that host aViewPageruse the support-libraryFragmentActivityclass as their base

a) True

b) False

Back 91

True

Front 92

ActionBar is only available in the latest version of Android.

a) True

b) False

Back 92

B. It's supported all the way back to Android 2.1

Front 93

What do you do to be notified of ActionBar item-clicks?

a) Subscribe to the ActionBar.ItemClick event

b) Pass an Action to the ActionBar constructor

c) Override an Activity method

Back 93

C. Override OnOptionsItemSelected

Front 94

DrawerLayout is a layout manager that provides a flyout menu

a) True

b) False

Back 94

a

Front 95

You instantiate an ActionBarToggleButton in code, not XML

a) True

b) False

Back 95

A

Front 96

What are the 2 accessibility strings required by the ActionBarToggleButton?

Back 96

DrawerOpenDescription and DrawerCloseDescription

Front 97

ActionBarDrawerToggle and DrawerLayout have references to each other so that they can work together

a) True

b False

Back 97

True. This is so that if you open or close the drawer in one class, the other will know and can react accordingly (eg open the drawer with swipe the ActionBarDrawerToggle button can update its icon)

Front 98

How do you configure a gesture recognizer so that it doesn't prevent built in gestures from firing?

Back 98

tapGesture.Recognizer.CancelsTouchesInView = false;

Front 99

What is a discrete gesture?

Back 99

It only fires the first time the gesture is recognized.

Front 100

When should you use a MapView vs MapFragment?

Back 100

MapView should be used if your app is comprised of fragments. MapFragment should be used if you are going to put the map class inside an activity.

Front 101

You must do all of the google maps work on the UI thread?

a) True

b) False

Back 101

a

Front 102

How can you ensure there is a map application present?

a) StartActivity

b) ActionView

c) ResolveActivity()

d) Android.Net.Uri.Parse()

Back 102

c

Front 103

What optional component must be included in the Android SDKManager?

a) Google Play Services

b) Android Support Repository

c) Google Repository

d) Google Play Licensing Library

Back 103

a

Front 104

Which emulator images have Play Services pre-installed?

a) Android SDK Build-tools

b) Google APIs (x86 System Image)

c) Google APIs (ARM System Image)

d) SDK Platform

Back 104

b,c

Front 105

You can use the same API key on more than one development machine(True or False)?

a) True

b) False

Back 105

a

Front 106

How does Google Play Services authenticate your application?

a) Shared password

b) API key + SHA1 keystore fingerprint + package name

c) X.509certificate d) No authentication necessary

Back 106

b

Front 107

Which permissions must be added to the Android manifest? (Select allthat apply)

a) INTERNET

b) ACCESS_NETWORK_STATE

c) ACCESS_FINE_LOCATION

d) WRITE_EXTERNAL_STORAGE

Back 107

a,b,d

Front 108

What classes are used to add the map visualization into the UI screen?

a) MapView

b) MapFragment

c) GoogleMap

d) Both A and B

Back 108

d

Front 109

Which class should be used to host a map in a fragment?

a) OnCreateView

b) MapFragment

c) FindViewByID

d) MapView

Back 109

d

Front 110

Google Maps raises the InfoWindowClick event when the user tapson a displayed info window popup for a marker.

a) True

b) False

Back 110

a

Front 111

What does the CameraPosition identify?

a) Tilt

b) Zoom

c) Target

d) All the above

Back 111

d

Front 112

What class do you use to create an update request?

a) CameraUpdateFactory

b) CameraUpdate

c) CameraPosition

d) None of the above

Back 112

a

Front 113

Android lifecycle:

Running

Paused

Backgrounded - Remains active in memory

Stopped - Removed from memory when the user presses the back button or android runs out of memory

Back 113

Yep

Front 114

Lifecycle methods:

OnCreate()

OnStart()

OnResume()

OnPause()

OnStop() - activity is backgrounded. Either go to OnRestart or OnDestroy next

OnDestroy() - Activity is stopped

Back 114

Yes

Front 115

What method do you call to start a service?

Back 115

context.StartService(new Intent(this, typeof(MyService)));

Front 116

Types of services

Back 116

Started - manually started

Bound - started on demand

Hybrid - started + bound

Front 117

Started Service lifecycle

Back 117

Call to StartService()

OnCreate()

OnStartCommand() - Service is now running

OnDestroy()

Front 118

Bound Service lifecycle

Back 118

Call to BindService()

Service running? No, call OnCreate()

Yes, OnBind() - Service running

Call to UnbindService()

OnUnbind()

All clients unbound? No goes to Service Running

Yes - OnDestroy()

Front 119

Android activity lifecycle

Back 119

OnCreate()

OnStart()

OnResume()

OnPause() - Goes back to OnResume()

OnStop()

OnRestart() - Goes back to OnStart()

OnDestroy()

Front 120

How much code is typically shared or platform specific?

Back 120

iOS - 70% shared, 30% platform

Android - 86% shared, 14% platform

WinMo - 85% shared, 15% platform

Front 121

The main thing that makes code sharable across platform is _______

a) When it is related to I/O

b) When it comes from Nuget

c) When it does not depend on anything platform APIs

d) All of the above

Back 121

c

Front 122

Which of the following might be possible candidates for sharing?

a) Code that accesses a Web Service accessing HttpClient

b) Validation rules for my UI which uses Regex and return bools

c) Code that uses local notifications on the device

d) Code that runs an algorithm to compare flight prices in parallel

Back 122

a,b,d

Front 123

Platform Specific Code Strategies

Back 123

Conditional Compilation

Class Mirroring

Partial Classes + Methods

Front 124

Class Mirroring

Back 124

Basically uses dependency injection (DI) to figure out which class/method to call at runtime.

Front 125

What types of files can you add to a Shared Project?

a) Source Code only

b) Source and Image assets

c) Source and Data files

d) Anything supported by the targets using the project

Back 125

d

Front 126

In PCL's, what are the 3 methods for using platform specific code?

Back 126

Callbacks, factories, and DI

Front 127

Event based

Back 127

Call an event whenever you want platform specific code executed.

Front 128

Shared Project Pros and cons

Back 128

Pros:

All APIs available

Platform-specific logic can be added directly

All file types can be shared

Cons:

Can lead to spaghetti code

Cannot be united tested on its own

Must be shipped in source form

Front 129

Portable Class Libraries Pros and cons

Back 129

Pros:

Enforces architectural design

Can be unit tested on its own

Can be shipped in binary form (Nuget)

Cons:

Limited APIs available

Difficult to share non-code files

Requires more work to integrate platform specific code

Front 130

Which of the following is not a platform supported by PCLs.

a) .NET2.0

b) Windows Phone 8.0 (Silverlight)

c) Windows Phone 8.1

d) Windows Store Apps

Back 130

a

Front 131

For Xamarin Forms, a Page represents a screen and a View is a control.

a) True

b) False

Back 131

a

Front 132

You must call _________ before using Xamarin.Forms

a) Forms.Initialize

b) Forms.Init

c) Forms.Setup

d) No setup call necessary.

Back 132

b

Front 133

To supply the initial page for the application, you must set the _______property.

a) Application.FirstPage

b) Application.PrimaryPage

c) Application.MainPage

d) Application.MainView

Back 133

c

Front 134

The direction (left-to-right or top-to-bottom) a StackLayoutorganizes content is controlled by which property?

a) Style

b) Direction

c) Orientation

d) LayoutDirection

Back 134

c

Front 135

Which of these controls is not available in Xamarin.Forms?

a) Button

b) DatePicker

c) ListBox

d) ListView

Back 135

c

Front 136

To adjust spacing between children when using the StackLayoutcontainer we can change the ______ property.

a) Margin

b) Padding

c) Spacing

Back 136

c

Front 137

Padding is the amount of space between the views and the edges of the page

a)True

b)False

Back 137

a

Front 138

What platform-specific features does Xamarin Forms have built-in?

Back 138

Devic.OpenUri

Alert Messages (Page.DisplayAlert)

Timer (Device.StartTimer)

UI Thread marshaling (Device.BeginInvokeOnMainThread)

Mapping (Xamarin.Forms.Maps)

Front 139

What type of dependency injection (DI) does Xamarin.Forms provide?

Back 139

Service locator

Front 140

How do you specify a dependency in Xamarin.Forms?

Back 140

[assembly: Dependency(typeof(PhoneDialerIos))]

Front 141

How do you get an instance of a service using DI in Xamarin.Forms?

Back 141

IDialer dialer = DependencyService.Get();

if (dialer != null) {

...

}

Front 142

How do you check for network status on Android?

Back 142

ConnectivityManager connectivityManager = (ConnectivityManager) Application.Context.GetSystemService(Context.ConnectivityService);

bool isConnected = connectivityManager.ActiveNetworkInfo != null&& connectivityManager.ActiveNetworkInfo.IsConnected;

Front 143

How do you check network status on iOS?

Back 143

bool isConnected = Reachability.InternetConnectionStatus()!= NetworkStatus.NotReachable

Front 144

How do you check if the network is reachable in Windows phone (WP)?

Back 144

bool isConnected = DeviceNetworkInformation.IsNetworkAvailable;

Front 145

How do you monitor if the network goes down in Android?

Back 145

Subscribe to the BroadcastReceiver ConnectivityChangeReceiver

android.net.conn.CONNECTIVITY_CHANGE

Front 146

How do you monitor if the network goes down in iOS?

Back 146

Reachability.ReachabilityChanged += (sender, args) => isConnected = Reachability.InternetConnectionStatus() != NetworkStatus.NotReachable

Front 147

How do you monitor network changes on Windows Phone (WP)?

Back 147

DeviceNetworkInformation.NetworkAvailabilityChanged +=(sender, e) => isConnected = e.NetworkInterface.InterfaceState == ConnectState.Connected;

...

NetworkChange.NetworkAddressChanged += (sender, e) =>isConnected = DeviceNetworkInformation.IsNetworkAvailable;

Front 148

How do you determine the network type on Android?

Back 148

NetworkInfo netInfo = connectivityManager.ActiveNetworkInfo; ConnectivityType currentNetworkType = netInfo.Type;

if (currentNetworkType == ConnectivityType.Wifi) {... }

else if (currentNetworkType == ConnectivityType.Mobile)

{... }

Front 149

How do you determine the network type on iOS?

Back 149

var status = Reachability.InternetConnectionStatus();NetworkType currentNetworkType = (status == NetworkStatus.ReachableViaWiFiNetwork)? NetworkType.Wifi: (status == NetworkStatus.ReachableViaCarrierDataNetwork ? NetworkType.Cellular : NetworkType.None;

Front 150

How do you determine the network type on Windows Phone (WP)?

Back 150

NetworkInterfaceInfo networkInterfaceInfo = new NetworkInterfaceList().FirstOrDefault(n => n.InterfaceState == ConnectState.Connected);

NetworkType networkType = NetworkType.None;if (networkInterfaceInfo != null && networkInterfaceInfo.InterfaceType == NetworkInterfaceType.Wireless80211){ networkType = NetworkType.Wifi;}

Front 151

You can detect roamin on Android and Windows Phone (WP), but it is platform specific.

Back 151

True

Front 152

How do you detect roaming on Android?

Back 152

ConnectivityManager connectivityManager =(ConnectivityManager)Application.Context .GetSystemService(Context.ConnectivityService);

bool isRoaming = (connectivityManager != null &&connectivityManager.ActiveNetworkInfo.IsRoaming);

Front 153

How do you detect roaming on Windows Phone (WP)?

Back 153

bool isRoaming = DeviceNetworkInformation.IsCellularDataRoamingEnabled;

Front 154

Is there a nuget package for cross-platform network detection?

Back 154

Yes. github.com/jamesmontemagno/Xamarin.Plugins

Front 155

POST is used to create resources when the service decides the location

Back 155

True

Front 156

PUT is used to update or create resources when the ID is passed in

Back 156

True

Front 157

Safe HTTP methods do not modify that resource representation. They allow for proxy caching etc for faster performance.

Back 157

OPTIONS yes

GET yes

PUT no

DELETE no

HEAD yes

POST no

PATCH no

Front 158

Idempotent HTTP methods can becalled multiple times with the samedata and it will always produce thesame result on the server (e.g. noside effects)

Back 158

OPTIONS yes

HEAD yes

POST no

PATCH no

Front 159

Pay attention to status codes andreissue requests to idempotent andsafe operations when outcome isuncertain (timeout, etc.)

Back 159

True

Front 160

HttpClient is supported in .NET, Android, and iOS apps natively. To use it in Windows Phone (WP), you need to install a Nuget package.

Back 160

True

Front 161

What are some HttpClient Get methods?

Back 161

GetStringAsync - returns the body

GetStreamAsync

GetByteArrayAsync

GetAsync - returns full HttpResponseMessage which includes headers + body+ status

Front 162

System.Json is not supported in PCLs

Json.NET is.

Back 162

True

Front 163

REST is an architectural style based on the architecture of _________

a) HTTP and XML

b) TCP/IP networking

c) The World Wide Web (WWW)

d) None of the above

Back 163

c

Front 164

Typically you use HttpClient to communicate with a REST based web service.

Back 164

True

Front 165

HttpClient is not as efficient as the native iOS and Android networking libraries.

Back 165

True

Front 166

ModernHttpClient is a Nuget package that works on iOS and Android. It has a different implementation for iOS and Android which gives you performance improvements.

Back 166

True

Front 167

In iOS 9, Apple created App Transport Security (ATS). It requires TLS 1.2 or better. You must use a cipher algorithm that provides forward security and certificates must be signed with SHA256, 2048-bit RSA key or better. It is enforced anytime you rely on underlying iOS networking, which ModernHttpClient does.

Back 167

True

Front 168

If you have an ATS problem, you will most likely get an exception that the connection is a non-TLS endpoint.

Back 168

True

Front 169

You can add NSAppTransportSecurity to your info.plist to get around ATS. You can also disable ATS by default.

Back 169

True

NSAppTransportSecurity

NSAllowsArbitraryLoads

Front 170

SOAP used HttpPost command

Back 170

True

Front 171

Using WCF with Xamarin requires a business edition license and a windows machine with the Silverlight SDK.

Back 171

True

Front 172

When using WCF, client and server have to agree on ABC's - Address, Binding, and Contract. Contract is typically an Interface.

Back 172

True

Front 173

User preferences are good for storing app configuration and other things that the user can control.

Back 173

True

Front 174

All 3 platforms support text, binary, XML and JSON file formats

Back 174

True

Front 175

For Android, the file location path is /files.

To get it, use Environment.GetFolderPath(Environment.SpecialFolder.Personal);

Back 175

True

Front 176

For iOS, the file location path is /Library/[subdirectory].

var docFolder = Environment.GetFolderPath(Environment.SpecialFolder.Personal);

libFolder = Path.Combine(docFolder, "..", "Library");

Back 176

True

Front 177

For Windows Phone (WP), the location path is \local

Windows.Storage.ApplicationData.Current.LocalFolder.Path;

Back 177

True

Front 178

How do you specify a file not be backed up by iCloud?

Back 178

void AddSkipBackupAttribute(string filename)

{ if (File.Exists(filename))

{// Do not backup to iCloud NSFileManager.SetSkipBackupAttribute(filename, true);

}

}

Front 179

On iOS, the documents folder is backed up by default.

Back 179

True

Front 180

In iOS, the library folder is where you store files that are not created by the user (database, etc). This folder is never exposed to the user in iTunes. It IS backed up.

Back 180

True

Front 181

SQLite is built into Android and iOS, but NOT Windows Phone.

Back 181

True

Front 182

When installing SQLite for Windows Phone (WP), you need to add a reference to Visual C++ runtime.

Back 182

True

Front 183

SQLite.net is probably the best SQLite API to use. It supports iOS, Android, Windows Phone (WP) 8, and WinStore. It's stable. ADO.NET is considered legacy. Install the one by Frank Krueger

Back 183

True

Front 184

How do connect to a SQLite db?

Back 184

string filename = ...

SQLiteConnection conn = new SQLiteConnection(filename);

Front 185

SQLite db file goes where?

Back 185

Android: Path.Combine(personalFolder, "databases")

/databases

iOS: Path.Combine(personalFolder, "..", "Library)

/Library

WinPhone: ApplicationData.Current.LocalFolder.Path

\local

Front 186

For SQLite DB, it's better to use the same connection for a set of operations vs opening a new one each time.

Back 186

True

Front 187

How do you map a class to a table?

Back 187

[Table("people")]

public class Person{

// PrimaryKey must be numeric

[PrimaryKey, AutoIncrement,Column("_id")] public int Id { get; set; }

[MaxLength(250), Unique]

public string Name { get; set; }

Front 188

With SQLite, how do you create a table?

Back 188

SQLiteConnection conn;

...

conn.CreateTable();

Front 189

How do you create an entity in SQLite?

Back 189

int result = conn.Insert(person);

return result;

It returns the number of rows affected.

Front 190

How do you get records from SQLite?

Back 190

List people = conn.Table().ToList();

return people;

Front 191

SQLite can only have one outstanding operation at a time. If you want to use a connection with multiple thread, you must guard access with a lock.

Back 191

public int AddNewPerson(Person person) {

lock (guard) {

return dbConn.Insert(person);

}

}

Front 192

With SQLite, how do you create a table asynchronously?

Back 192

var conn = new SQLiteAsyncConnection(dbPath);...

await dbConn.CreateTableAsync();

Front 193

With SQLite, how do you asynchronously query the db?

Back 193

List people = await dbConn.Table().ToListAsync(); // Must be on UI thread here!

foreach (var p in people)

peopleList.Add(p);

Front 194

With SQLite, how do you run code in a transaction?

Back 194

int count = 0;

await conn.RunInTransactionAsync(iconn => { count += iconn.Insert(insertMe);

count += iconn.Update(updateMe)

});

return count;

Front 195

With SQLite, how do you execute a raw SQL query?

Back 195

List students = await conn.QueryAsync( "SELECT * FROM [students] WHERE id in " +"(SELECT sid FROM students_classes WHERE cid=?)", xam160.Id);

Front 196

With SQLite, how do you stay on the background thread after executing a query?

Back 196

Use ConfigureAwait(false)

var students = await dbConn.QueryAsync("...", class.Id).ConfigureAwait(false);

// Background thread continues execution here .. NOT ON UI THREAD!

foreach (var s in students) { ... }

Front 197

Registration fees for iOS?

Back 197

iOS: $99 / $299 annual. Unlimited number of apps. 20% of market. Higher daily revenue.

Android: $25, unlimited, 75% of market. Best searching, new apps found quickly.

WinMo: $19-$99 one-time. 100 free app listings. Less competition = more opportunity

Front 198

"Link SDK Assemblies only" will reduce the size of your app by discarding unused assemblies, types, and members. Sometimes this will remove stuff you need, so make sure you test it.

Back 198

True

Front 199

On iOS, always use the Unified API to support 64-bit, it is required by Apple.

Back 199

True

Front 200

Can bundle ARMv7 and ARM65 in a single app bundle.

Back 200

True

Front 201

Recommended to use LLVM and SGen garbage collector for better runtime performance.

Back 201

True

Front 202

Android deploy settings depend on which license type of Xamarin you have.

Back 202

Enterprise - allows you to embed managed code into navtive shared library

ProGurad for obfuscating and shrinking java bytecode.

Business - AOT performs JIT when app is installed vs when it is run.

LLVM - generates smaller, faster code.

Front 203

It is an Apple requirement to build against the latest SDK.

Back 203

True

Front 204

On iOS, deployment target is the lowest version of iOS that you support.

Back 204

True

Front 205

Info.plist stores icons, launch images, and identifies the launch screen for iOS8.

Back 205

True

Front 206

A startup screen can be definined in a storyboard or xib and use auto layout to automatically resize an image. That way you only need 1 definition.

Back 206

True

Front 207

Retina displays use @2x images and plus phones use @3x.

Back 207

true

Front 208

3 publishing methods for iOS - adhoc, AppStore, and Enterprise.

Back 208

True

Front 209

AdHoc allows for up to 100 devices per year to be used. App is installed directly on the device. Invite by email.TestFlight automates the process for iOS8 and above.

Back 209

True

Front 210

Enterprise is for large companies to distribute apps in-house either through iTunes or OTA from your own servers. Must have enterprise level account and meet Apple requirements. App certificate expires after some time and must be re-signed to continue distribution.

Back 210

True

Front 211

For AppStore, you need to do these things: Generate a distribution cert, generate a provisioning profile, create an AppID, assign identify and sign app with certs, and generate package and upload to iTunes Connect or distribute ipa as enterprise app.

Back 211

True

Front 212

On iOS, the developer certificate is need to sign debug versions of your app that you want to test on physical devices. You need it to deploy locally to a device you own.

Back 212

True

Front 213

Push Notifications Cert is needed to communicate with Apple's test servers. Only to be used for testing.

Back 213

True

Front 214

AppStore/AdHoc Cert - The primary cert. It is needed to sign the app and identify it as trusted by any device (since it comes from Apple)

Back 214

True

Front 215

You also need different production certificated for each unique Apple server-side service you use. Eg Safari Push notifications, VOIP, Apple Pay, Passbook.

Back 215

True

Front 216

The Provisioning Profile is used to glue all the pieces together – itassociates a distribution certificate, an App ID, and a set of device IDsand indicates where the application signed with this certificate can run –there are four types of provisioning profiles you can create:

Back 216

True

Front 217

iOS App developer provisioning profile is used to install apps on local developer devices, devices must be registered.

Back 217

True

Front 218

AdHoc provisioning profile type is used to install apps on specific test users devices (limited).

Back 218

True

Front 219

AppStore provisioning profile type has no device restrictions - deployed through the AppStore and can only be created by the team agent or admin

Back 219

True

Front 220

Enterprise provisioning profile type has no device restrictions. It's deployed through internal corporate delivery, typically OTA and can only be created by the agent/admin.

Back 220

True

Front 221

With Apple TestFlight, you can invite internal and external users to test the app. The system will automatically track the UUID of the device and generate the cert.

Back 221

True

Front 222

HockeyApp is a Microsoft testing distribution platform which supports all major mobile platforms. No forced approval process like TestFlight, can invite testers through email, limited to 100 devices per app, and supports analytics with optional SDK.

Back 222

True

Front 223

In Android, the target should be the latest framework but the min version should be the lowest version the app supports.

Back 223

True

Front 224

In Android, package name must be lowercase.

Back 224

True

Front 225

MDPI - 1x 48px

HDPI - 1.5x 72px

XHDPI - 2x 96px

XXHDPI 3x 144px

XXXHDPI 4x 192px

Back 225

True

Front 226

On Android, the keystore is a private key cert used to sign your application and identify you as the publisher.

Back 226

True

Front 227

In android, there are 2 publishing methods - sideloading and Store publishing,

Back 227

True

Front 228

Amazon AppStore developer accounts are free.

Back 228

True

Front 229

Xamarin.Forms targets WP8 SL

Back 229

True

Front 230

For publishing a Windows Phone (WP) app, fill in the WPAppManifest.xml file.

Back 230

True

Front 231

For Windows Phone (WP), the tile icons you need are Normal (300x300), small (159x159), and Wide (691x336).

Back 231

True

Front 232

For Windows Phone (WP), you must have 1 screenshot and localized description for every supported language. You must also support light and dark themes.

Back 232

True

Front 233

Verify your Windows Phone (WP) app with the "Windows Phone Store Test Kit" prior to submission.

Back 233

True

Front 234

On Windows Phone (WP), you can do beta publication on up to 10,000 specific devices. You invite by email.

Back 234

True

Front 235

Another publishing model for Windows Phone (WP) is to submit to the marketplace but hidden. Only people that have the URL can install it. (Targeted App Distribution)

Back 235

True

Front 236

dev.windows.com is the developer portal. Can use the same account for Windows Phone (WP) and Windows Store Apps.

Back 236

True

Front 237

Microsoft supports an enterprise cert which is tied to a company and used to sign internal XAPs. Requires some command-line finesse to create a signed XAP. Companies can create a "Company Hub" app for internal app discovery and installation.

Back 237

True

Front 238

UriImageSource also supports caching of downloaded images, configured through the following properties:CachingEnabled - Whether caching is enabled ( true by default). CacheValidity - A TimeSpan that defines how long the image will be stored locally. Caching is enabled by default and will store the image locally for 24 hours. To disable caching for a particular image, instantiate the image source like this:

Back 238

True

Front 239

How to launch maps app in iOS?

Back 239

UIApplication.SharedApplication.OpenUrl(new NSUrl("http://maps.apple.com/?address=1,Infinite+Loop,Cupertin,California"));

Front 240

How to create a map view using mapkit through code?

Back 240

MKMapView map = new MKMapView(UIScreen.MainScreen.Bounds);

View.Add(map);

Front 241

What are the different iOS map styles available?

Back 241

Standard, Satellite, Hybrid, and Flyover (iOS9+) & Hybrid Flyover.

Front 242

CoreLocation is Apple's framework that providescoordinate-based information by retrieving locationand heading data from the iOS device hardware

Back 242

True

Front 243

CLLocationManager is the central pointfor location services in CoreLocation § Current location§ Monitor location changes§ Monitor heading changes (compass)§ Geofencing support§ Beacon regions (BLE) v Often used with MapKit, but can be usedindependently

Back 243

True

Front 244

How to use location manager directly?

Back 244

lm = new CLLocationManager { DesiredAccuracy = 1000 } ;

Front 245

void OnLocationChanged(object sender, CLLocationsUpdatedEventArgs e)

{

CLLocation newLocation = e.Locations[e.Locations.Length - 1]; UpdateUI(newLocation);

}

Back 245

Most recent location is the last item in the array.

Front 246

How do you turn off power-saving mode while monitoring location changes?

Back 246

lm = new CLLocationManager { DesiredAccuracy = 1000 }; lm.PausesLocationUpdatesAutomatically = false;

Front 247

In iOS8 and beyond, location permissions are split into two types ofauthorization, one of which must be requested by the app. How do you request "in-use" permission?

Back 247

Only available on iOS 8+, so check the version the user is running first.

if(UIDevice.CurrentDevice.CheckSystemVersion (8, 0))

{ locationManager.RequestWhenInUseAuthorization();

}

Front 248

Always permission allows an app to receive notifications even if the app is moved to the background. How do you request "always" permission?

Back 248

if (UIDevice.CurrentDevice.CheckSystemVersion (8, 0))

{ locationManager.RequestWhenAlwaysAuthorization();

}

Front 249

Maps iOS NSLocationWhenInUseUsageDescription specifies the message to display the first time your application calls RequestWhenInUseAuthorization.

Back 249

True

Front 250

iOS Maps -NSLocationAlwaysUsageDescription

Specifies the message to display thefirst time your application callsRequestAlwaysAuthorization

Back 250

True

Front 251

Add the NSLocationAlwaysUsageDescription and NSLocationWhenInUseUsageDescription to the info.plist on the "source" tab.

Back 251

True

Front 252

How do you monitor authorization change for iOS maps location?

Back 252

locationManager.AuthorizationChanged += (sender, e) => {

if (e.Status != CLAuthorizationStatus.Denied) {

// Location permissions allowed

}

};

Front 253

In iOS maps, how do you show the users location?

Back 253

map.ShowsUserLocation = true;

Front 254

On iOS maps, CenterCoordinate defines the center of the map in lat/long coordinates.

Back 254

True

Front 255

Altitude defines how far away from the ground the camera is in meters.

Back 255

True

Front 256

Pitch defines the 3D angle of the camera with respect to the ground 0°indicates looking straight down; can slide two fingers to adjust pitchinteractively on real devices

Back 256

True

Front 257

Heading changes the compassdirection – which way is "up" on themap. It is expressed in degrees where zero(default) corresponds to true North

Back 257

True

Front 258

How to change the map centercoordinate, altitude, pitch, and heading in code?

Back 258

map.Camera.CenterCoordinate = locMgr.Location;

map.Camera.Altitude = 1000.0;

map.Camera.Pitch = 45.0f;

map.Camera.Heading = 180.0;

Front 259

In iOS maps, how do you show a specific region?

Back 259

double distanceInMeters = 2000;MKCoordinateRegion region = MKCoordinateRegion.FromDistance( new CLLocationCoordinate2D(42.3, -71.0589), distanceInMeters, distanceInMeters);

map.SetRegion(region, true) // animate to the new region

Front 260

In iOS maps, how do you detect if the region changes?

Back 260

map.RegionChanged +=delegate (object sender, MKMapViewChangeEventArgs e)

{

if (map.Camera.Altitude > 100)

{

map.Camera.Altitude = 99;

}

};

Front 261

How do you add an annotation to iOS maps?

Back 261

var ptAnnotation = new MKPointAnnotation

{

Title = "Magilla’s Banana Store",

Subtitle = "Best Bananas in town!",

Coordinate = new CLLocationCoordinate2D (42.5, -71.0)

};

map.AddAnnotation(ptAnnotation);

Front 262

How to remove an annotation on iOS maps?

Back 262

map.RemoveAnnotation(selectedAnnotation);

map.RemoveAnnotations (map.Annotations);

Front 263

How to adjust the iOS maps viewport to show all annotations?

Back 263

map.ShowAnnotations(map.Annotations, true);

True is for animating the movement.

Front 264

Bridge pattern is when you code to an interface and provide the implementation somewhere else. Basically like using DI.

Back 264

True

Front 265

Factory pattern - Dependencies can be located through factories which are responsiblefor creating the abstractions

Back 265

True

Front 266

One way to use a factory pattern is to have a service store a delegate that points to the implementation.

Back 266

True

Front 267

Pros and cons of factory

Back 267

Pro: Hides the implementation

Easy to use and understand

Can decide implementation at runtime and return specific version based on environment.

CONS: Requires a separate factory for each abstraction (maint issue)

Client must take dependency against factory

Missing dependencies are not known until runtime.

Front 268

Service Locator pattern uses a container that maps abstractions(interfaces) to concrete, registered types – client then uses locator to finddependencies. Service locator is a singleton.

Back 268

True

Front 269

With a service locator, you register implementations for the abstractions in startup code.

Back 269

True

Front 270

To use the service locator, you ask the service locator for an instance of a service.

Back 270

var alert = ServiceLocator.Instance.Resolve();

Front 271

Examples of Service locators are:

Common Service Locator

Most Mvvm libraries

Xamarin.Forms DependencyService

Back 271

True

Front 272

Service locator pros and cons

Back 272

Pro: Easyto understand

Clients can JIT-request services

Can be used with any client

CONS: Clients must all have access to the locator

Harder to identify dependencies in code

Missing dependencies harder to detect

Front 273

IoC containers create types and automatically supply the dependencies.

Back 273

True

Front 274

DI Container pros and cons

Back 274

Pros: Created client only needs real dependencies, no container references needed

Easy to identify dependencies used since they are passed to constructor or properties

Missing dependencies found earlier than SL

CONS: Involves a bit of magic. A little harder to understand.

Often requires some form of reflection, could be a performance hit.

Clients can't request dependencies once they've been created/initialized.

Front 275

Service Locator is where ___________.

a) Services are found and set into properties on the client

b) Client request specific abstraction through a shared locator

c) Client creates service directly

d) You use Accio summoning charm to create the service.

Back 275

b

Front 276

Garbage collection is mapped on top of the platform memory management. On iOS there are 2 choices, prefer sgen over default.

Back 276

True

Front 277

If you are making an async call and you don't care what thread it returns to (eg you don't need to do anything on the UI thread immediately when it returns) use ConfigureAwait(false) on the call. It will result in a performance increase.

Back 277

var stuff = await client.doStuff().ConfigureAwait(false);

Front 278

When the garbage collector runs, it pauses your app.

Back 278

True

Front 279

Garbage collector kicks in when you request to allocate memory and there is not enough available.

Back 279

True

Front 280

Garbage collector compacts the heap in addition to freeing up objects.

Back 280

True

Front 281

Sgen has 3 heaps. Nursery, Major, and large (> 8k) objects.

Back 281

True

Front 282

Freeing up objects in nursery is cheap.

Back 282

True

Front 283

To prevent references from keeping object in memory, use weak references when you have a parent/child relationship (parent is a property on the child object). Set things like UIViews to null or manually call dispose on them.

Back 283

True

Front 284

Image caching: Use weak references because UIView uses an unmanaged resource so the garbage collector doesn't know how much memory it's using. Also manually dispose of image view objects.

Back 284

True

Front 285

Java bindings: - 2 options. JNI or a bindings library. JNI is quicker to get going but tedious to code and verbose.

Back 285

True

Front 286

You can create bindings for jar and aar files.

Back 286

True

Front 287

When binding Android jar files, you can choose to embed the jar into your binding library or have it separate aka "Input Jar".

Back 287

True

Front 288

Xamarin supports calling WCF with BasicHttpBinding and supports SSL.

Back 288

True

Front 289

xamarin.social supports

App.net

Facebook

Flickr

Twitter

Back 289

True

Front 290

Xamarin.Mobile is a library that exposes a single set of APIs for accessing common mobile device functionality across iOS, Android and Windows platforms.

Back 290

True

Front 291

To run code on the UI thread, use:

InvokeOnMainThread ( () =>

{

// manipulate UI controls

});

Back 291

True