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Building your first android app using Xamarin


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Do you have a great knowledge about C#? Maybe you’ve already built a great mobile app on Windows Phone or Windows 8? Would you like to be able to use your knowledge to build an Android app without having to resort to other languages or IDEs? Well, now you can! With Xamarin. In this session, Gill Cleeren will take you through the creation of your first Android application. We’ll see how we can use our trusted Visual Studio for this task, how we can create apps with mulitple screens and how we can call services. We’ll also look at how we can deploy the application and how we can debug our code.

Published in: Software, Mobile
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Building your first android app using Xamarin

  1. 1. Building your first Android app using Xamarin Gill Cleeren - @gillcleeren
  2. 2. Hi, I’m Gill! Gill Cleeren MVP and Regional Director .NET Practice Manager @ Ordina Trainer & speaker @gillcleeren
  3. 3. I’m a Pluralsight author! • Courses on Windows 8, social and HTML5 •
  4. 4. Agenda • Overview of Xamarin and Xamarin.Android • Xamarin.Android fundamentals • Creating a detail screen • Lists and navigation • Navigating from master to detail • (Optional) Intro to using Fragments • Optimizing the application • Preparing for store deployment
  5. 5. Targets of this talk • Understanding the fundamentals of Android app development with Xamarin • See how a fully working app can be built
  6. 6. The demo scenario • Android Coffee Store Manager • List of coffee • Navigation to details page
  7. 7. DEMO Looking at the finished application
  8. 8. Overview of Xamarin and Xamarin.Android
  9. 9. Hello Xamarin • Xamarin enables developers to reach all major mobile platforms! • Native User Interface • Native Performance • Shared Code Across Platforms • C# & .NET Framework • Toolset on top of Visual Studio • Enables VS to create native iOS and Android apps • Commercial product
  10. 10. Write Everything in C# iOS, Android, Windows, Windows Phone, Mac Billions of Devices covered!
  11. 11. The Xamarin platform Xamarin Xamarin.Android Xamarin.iOS Xamarin Forms
  12. 12. Xamarin.Android exposes many extra device types
  13. 13. Xamarin.Android Anything you can do in Java/Android can be done in C# and Visual Studio (or Xamarin Studio) with Xamarin!
  14. 14. How Xamarin works on Android • Mono VM + Java VM execute side-by-side (supports both Dalvik and ART) • Mono VM JITs IL into native code and executes most of your code • Can utilize native libraries directly as well as .NET BCL
  15. 15. A word on code-sharing • Xamarin brings development time through the use of code-sharing • Possible (currently!) using • Shared projects: • allows organizing the shared code • #if directives for platform specific code • PCL • “include” the platforms we want to support • Abstract to interfaces where platforms have specific implementations
  16. 16. Target architecture for a Xamarin app
  17. 17. Preparing for Android development
  18. 18. What you need for Xamarin.Android development • Xamarin license (Xamarin.Android) • PC or Mac • Visual Studio or Xamarin Studio • Android SDK and Emulators (installed via Xamarin setup) • Emulator • Device (not really required but...)
  19. 19. Installing Xamarin.Android
  20. 20. A word on emulators • Setup will install some basic emulators for you • They’re great… for drinking a lot of coffee
  21. 21. Alternatives for the default emulators • Possible options • Genymotion -Requires VirtualBox under the hood • HAXM drivers • Android Player from Xamarin • Microsoft Android emulator • Hyper-V
  22. 22. Developing with a device • 3 steps • Enable Debugging on the Device • Install USB Drivers (Windows only) • Connect the Device to the Computer
  23. 23. Enable device debugging • Tap the Build number 7 times to reveal developer options
  24. 24. DEMO A quick look at the development setup
  25. 25. Xamarin.Android fundamentals
  26. 26. File  New Project
  27. 27. File  New Project
  28. 28. Fundamental #1: Activities • Apps are collections of activities • A view == an activity (for now ) • Apps don’t have an “entry point” • No single code line which is called by the OS • Apps start when Android creates one of the classes of the app • App then gets loaded into memory
  29. 29. Fundamental #1: Activities • When opening an application, the OS creates the first Activity • Activity is a specific class • Defines UI and behaviour for a single task • Corresponds to a single app screen • App gets loaded in memory OS User launches app Activity Android loads app In memory
  30. 30. Fundamental #1: Activities • One activity needs to be the “entry point” for the app: MainLauncher=True
  31. 31. Activity lifecycle
  32. 32. Activity lifecycle • We can of course override these methods • OnCreate: • Create views, initialize variables, and do other prep work before the user sees the Activity • This method is called only once when the Activity is loaded into memory • OnResume • Perform any tasks that need to happen every time the Activity returns to the device screen • OnPause • Perform any tasks that need to happen every time the Activity leaves the device screen
  33. 33. Activity lifecycle in effect
  34. 34. Fundamental #2: Views • The layout of the app is contained in *.axml files • AXML: Android designer file / Android XML • First view of the app is named Main.axml • Can be any name really • AXML files live in the Resources/layout folder
  35. 35. The designer for Xamarin.Android views
  36. 36. The designer for Xamarin.Android views
  37. 37. View code
  38. 38. Connecting and accessing controls from code • Linking a view with an activity is done using SetContentView
  39. 39. Connecting and accessing controls from code • We can name controls using the ID property • The Android designer maps the control to the Resource class and assigns it a resource ID • The code representation of a control is linked to the visual representation of the control in the designer via the Id property
  40. 40. Connecting and accessing controls from code • Once we have created the controls, we can access them from code • Field name is used for lookup
  41. 41. Fundamental #3: Application manifest • An Android app contains a manifest file • Contains a list of all resources, properties… that make up the application • Also contains name, list of permissions… that the application has received Images Icons *.axml Others Android Manifest file
  42. 42. DEMO Creating our first Android application together!
  43. 43. Navigation and lists
  44. 44. Fundamental #4: ListViews and adapters • Used very commonly in Android • Common way to present lists of rows • Each row is represented using a standard style or customized • Consists out of • ListView: visual part • Adapter: feeds data to ListView
  45. 45. Fundamental #4: ListViews and adapters
  46. 46. Important classes • ListView • ListActivity • BaseAdapter • ArrayAdapter & ArrayAdapter<T>
  47. 47. ListActivity and the built-in ArrayAdapter<T> [Activity(Label = "Coffees", MainLauncher = true, Icon = "@drawable/icon")] public class CoffeeScreenActivity: ListActivity { string[] coffees; protected override void OnCreate(Bundle bundle) { base.OnCreate(bundle); coffees= new string[] { "Coffee 1","Coffee 2", "Coffee 3"}; ListAdapter = new ArrayAdapter<String>( this, Android.Resource.Layout.SimpleListItem1, coffees); } }
  48. 48. Implementing your own adapter • In most cases, the ArrayAdapter won’t be enough • We’ll need to create our own adapter • Inherits from BaseAdapter • Things we need to implement • Count: • To tell the control how many rows are in the data • GetView: • To return a View for each row, populated with data. This method has a parameter for the ListView to pass in an existing, unused row for re-use • GetItemId: • Return a row identifier (typically the row number, although it can be any long value that you like) • this[int] indexer: • To return the data associated with a particular row number
  49. 49. Handling row clicks • To handle row clicks, we need to implement OnListItemClick protected override void OnListItemClick(ListView l, View v, int position, long id) { var t = items[position]; //do something }
  50. 50. DEMO Adding a ListView and an adapter
  51. 51. Customizing the ListView with other row views
  52. 52. Customizing the ListView with other row views
  53. 53. Customizing the ListView with other row views
  54. 54. DEMO Using the built-in row views
  55. 55. Creating your own row views • Custom row layouts are AXML files in Resources/layout • Are loaded by Id using a custom adapter • View can contain any number of display classes with custom colors, fonts…
  56. 56. Creating your own row view <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="" android:layout_width="fill_parent" android:layout_height="wrap_content" android:padding="8dp" android:orientation="horizontal"> <ImageView android:id="@+id/CoffeeImageView" android:layout_width="50dp" android:layout_height="50dp" android:padding="5dp" /> <LinearLayout android:id="@+id/TextFields" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="wrap_content" android:paddingLeft="10dip"> <TextView android:id="@+id/CoffeeNameText" android:layout_width="wrap_content" android:layout_height="wrap_content" /> <TextView android:id="@+id/PriceText" android:layout_width="wrap_content" android:layout_height="wrap_content" /> </LinearLayout> </LinearLayout>
  57. 57. Using your custom row view public override View GetView(int position, View convertView, ViewGroup parent) { //custom view var item = items[position]; if (convertView == null) { convertView = context.LayoutInflater.Inflate (Resource.Layout.CoffeeRowView, null); } convertView.FindViewById<ImageView> (Resource.Id.CoffeeImageView).SetImageResource( imageRepository.ImageNameToResourceInt(item.ImageId.ToString())); convertView.FindViewById<TextView> (Resource.Id.CoffeeNameText).Text = item.CoffeeName; convertView.FindViewById<TextView> (Resource.Id.PriceText).Text = item.Price.ToString(); return convertView; }
  58. 58. DEMO Adding our own custom row view
  59. 59. Fundamental #5: Intents • An Intent is an abstract concept for some sort of operation that should be performed in Android • Navigating to another activity • Often, launching an external application (= built-in) with the intent of doing something • Make a phone call • Launch a URI • Map an address • An intent often consist out of • What the intent is • The data needed for the intent • Phone number to call
  60. 60. Intent of making a phone call • ActionCall asks Android for an Activity to make a phone call
  61. 61. Intent of navigating to another screen • StartActivity can be used to start another activity • PutExtra() is used to pass data from one activity to the other var intent = new Intent (); intent.SetClass (this, typeof(CoffeeDetailActivity)); intent.PutExtra ("selectedCoffeeId", t.CoffeeId); StartActivity (intent);
  62. 62. Receiving information from the intent protected override void OnCreate (Bundle bundle) { base.OnCreate (bundle); SetContentView (Resource.Layout.Main); var selectedCoffeeId = Intent.Extras.GetInt ("selectedCoffeeId", 0); Coffee coffee = DataService.GetCoffeeById (selectedCoffeeId); }
  63. 63. DEMO Navigating from the List to the Detail page
  64. 64. Adding Fragments
  65. 65. The need for Fragments • Larger screen: more complex to build UIs that look good on all screens • Layouts which look good on a small screen may not look good on a large tablet screen • Android V3.0 introduced Fragments • Fragment is a UI module • UI gets divided into reusable parts • Each “part” is an separate activity • At run time, the Activities themselves will decide which Fragments to use • Also work in older versions through Support packages
  66. 66. The need for Fragments
  67. 67. FragmentManager • To help an Activity coordinate and manage all these Fragments, Android introduced a new class called the FragmentManager • Each activity has an instance of the FragmentManager • Allows finding, adding and removing fragments
  68. 68. Adding a fragment to an Activity • We can add the Fragment to the Activity in 2 ways • Declaratively: • Fragments can be used declaratively within .axml layout files by using the <Fragment> tag • Programmatically • Fragments can also be instantiated dynamically by using the FragmentManager class’s API
  69. 69. DEMO Refactoring to Fragments
  70. 70. Optimizing the application
  71. 71. Managing strings in strings.xml • We can have Android store string values for us <?xml version="1.0" encoding="utf-8"?> <resources> <string name="hello">Hello World, Click Me!</string> <string name="app_name">AndroidCoffeeStore</string> <string name="coffeeNameLabel">Coffee name</string> </resources> <TextView android:text="@string/coffeeNameLabel" android:layout_width="match_parent" android:layout_height="wrap_content" android:id="@+id/CoffeeNameLabel" />
  72. 72. Making the app multi-language
  73. 73. Application drawables • We can add drawables: application icons • Adding all resolutions makes sure the icons look good on all screens • Filenames are the same • Folder name identifies the resolution
  74. 74. Application drawables • We can select an image in the project properties • This now becomes the icon for the application within Android
  75. 75. DEMO Adding resources and drawables to the application
  76. 76. Deploying to the store
  77. 77. Publishing your work • Marketplace is most common option • Often, more than one is used (Google Play, Amazon, GetJar…) • Email or website is often for a more closed distribution • Also require less work to prepare the application for distribution • Google Play is best known store • Allows users to discover, download, rate, and pay for applications by clicking a single icon either on their device or on their computer • Google Play also provides tools to assist in the analysis of sales and market trends and to control which devices and users may download an application
  78. 78. Summary • Xamarin.Android leverages your C# knowledge to build apps for Android • Concepts of Android mean a learning curve
  79. 79. Thanks!
  80. 80. Q&A
  81. 81. Building your first Android app using Xamarin Gill Cleeren - @gillcleeren
  82. 82. Your feedback is important! Scan the QR Code and let us know via the TechDays App. Laat ons weten wat u van de sessie vindt via de TechDays App! Scan de QR Code. Bent u al lid van de Microsoft Virtual Academy?! Op MVA kunt u altijd iets nieuws leren over de laatste technologie van Microsoft. Meld u vandaag aan op de MVA Stand. MVA biedt 7/24 gratis online training on-demand voor IT- Professionals en Ontwikkelaars.