Gill Cleeren
Agenda Overview of Xamarin and Xamarin.Android Xamarin.Android fundamentals Creating a detail screen Lists and navigation Navigating from master to detail Optimizing the application Preparing for store deployment
Targets of this talk Understanding the fundamentals of Android app development with Xamarin See how a fully working app can be built
The demo scenario Android Coffee Store Manager List of coffees Navigation to details page
DEMO Looking at the finished application
Overview of Xamarin and Xamarin.Android
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
Write Everything in C# ios, Android, Windows, Windows Phone, Mac Billions of Devices covered!
The Xamarin platform Xamarin Xamarin.Android Xamarin.iOS Xamarin Forms
Xamarin.Android exposes many extra device types
Xamarin.Android Anything you can do in Java/Android can be done in C# and Visual Studio (or Xamarin Studio) with Xamarin!
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
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 Standard library Now becoming a possibility Wider range than PCL
Target architecture for a Xamarin app
Preparing for Android development
What you need for Xamarin.Android development Xamarin license (Xamarin.Android) Free with VS Community Edition PC or Mac Visual Studio or Visual Studio for Mac Android SDK and Emulators (installed via Xamarin setup) Emulator Device (not really required but...)
Installing Xamarin.Android
A word on emulators Setup will install some basic emulators for you They re great for drinking a lot of coffee
Alternatives for the default emulators Possible options Genymotion -Requires VirtualBox under the hood HAXM drivers Android Player from Xamarin Microsoft Android emulator Hyper-V
DEMO A quick look at the development setup
Xamarin.Android fundamentals
File New Project
File New Project
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
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 User launches app Activity Android loads app In memory OS
Fundamental #1: Activities One activity needs to be the entry point for the app: MainLauncher=True
Activity lifecycle
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
Activity lifecycle in effect
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
The designer for Xamarin.Android views
The designer for Xamarin.Android views
View code
Connecting and accessing controls from code Linking a view with an activity is done using SetContentView
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
Connecting and accessing controls from code Once we have created the controls, we can access them from code Field name is used for lookup
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 *.axml Icons Others Android Manifest file
DEMO Creating our first Android application together!
Navigation and lists
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
Fundamental #4: ListViews and adapters
Important classes ListView ListActivity BaseAdapter ArrayAdapter & ArrayAdapter<T>
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); }
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
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 }
DEMO Adding a ListView and an adapter
Customizing the ListView with other row views
Customizing the ListView with other row views
Customizing the ListView with other row views
DEMO Using the built-in row views
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
Creating your own row view <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/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>
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;
DEMO Adding our own custom row view
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
Intent of making a phone call ActionCall asks Android for an Activity to make a phone call
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);
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);
DEMO Navigating from the List to the Detail page
Optimizing the application
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" />
Making the app multi-language
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
Application drawables We can select an image in the project properties This now becomes the icon for the application within Android
DEMO Adding resources and drawables to the application
Deploying to the store
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
Summary Xamarin.Android leverages your C# knowledge to build apps for Android Concepts of Android mean a learning curve
Thanks!
Q&A