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Hello, Android: Quickstart

Introduction to Android development with Xamarin

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last updated: 2017-10

In this two-part guide, you will build your first Xamarin.Android application (using Visual Studio or Visual Studio for Mac) and develop an understanding of the fundamentals of Android application development with Xamarin. Along the way, you will be introduced to the tools, concepts, and steps required to build and deploy a Xamarin.Android application.

Hello, Android Quickstart

In this walkthrough, you will create an application that translates an alphanumeric phone number (entered by the user) into a numeric phone number and display the numeric phone number to the user. The final application looks like this:

Screenshot of app when it is complete

Requirements

To follow along with this walkthrough, you will need the following:

  • Windows 7 or later.

  • Visual Studio 2015 Professional or later.

  • The latest version of Visual Studio for Mac.

  • OS X Yosemite or later.

This walkthrough assumes that the latest version of Xamarin.Android is installed and running on your platform of choice. For a guide to installing Xamarin.Android, refer to the Xamarin.Android Installation guides. Before you get started, please download and unzip the Xamarin App Icons & Launch Screens set.

Configuring Emulators

If you are using Google's Android SDK emulator, we recommend that you configure the emulator to use hardware acceleration. Instructions for configuring hardware acceleration are available in Hardware Acceleration.

If you are using the Visual Studio Android Emulator, Hyper-V must be enabled on your computer. For more information about configuring the Visual Studio Android Emulator, see System Requirements for the Visual Studio Emulator for Android.

Walkthrough

  1. Start Visual Studio. Click File > New > Project to create a new project.

  2. In the New Project dialog, click the Blank App (Android) template. Name the new project Phoneword. Click OK to create the new project:

    New project is Phoneword

  3. After the new project is created, expand the Resources folder and then the layout folder in the Solution Explorer. Double-click Main.axml to open it in the Android Designer. This is the layout file for the app's screen:

    Open Main.axml

  4. From the Toolbox (the area on the left), enter text into the search field and drag a Text (Large) widget onto the design surface (the area in the center):

    Add large text widget

  5. With the Text (Large) control selected on the design surface, use the Properties pane to change the text property of the Text (Large) widget to Enter a Phoneword: as shown here:

    Set large text properties

  6. Drag a Plain Text widget from the Toolbox to the design surface and place it underneath the Text (Large) widget:

    Add plain text widget

  7. With the Plain Text widget selected on the design surface, use the Properties pane to change the id property of the Plain Text widget to @+id/PhoneNumberText and change the text property to 1-855-XAMARIN:

    Set plain text properties

  8. Drag a Button from the Toolbox to the design surface and place it underneath the Plain Text widget:

    Drag translate button to the design

  9. With the Button selected on the design surface, use the Properties pane to change the id property of the Button to @+id/TranslateButton and change the text property to Translate:

    Set translate button properties

  10. Drag a TextView from the Toolbox to the design surface and place it under the Button widget. Set the id property of the TextView to @+id/TranslatedPhoneWord and change the text to an empty string:

    Set the properties on the text view.

  11. Save your work by pressing CTRL+S.

  12. The next step is to add some code to translate phone numbers from alphanumeric to numeric. Add a new file to the project by right-clicking the Phoneword project in the Solution Explorer pane and choosing Add > New Item... as shown below:

    Add new item

  13. In the Add New Item dialog, select Visual C# > Code and name the new code file PhoneTranslator.cs:

    Add PhoneTranslator.cs

  14. This creates a new empty C# class. Insert the following code into this file:

    using System.Text;
    using System;
    namespace Core
    {
        public static class PhonewordTranslator
        {
            public static string ToNumber(string raw)
            {
                if (string.IsNullOrWhiteSpace(raw))
                    return "";
                else
                    raw = raw.ToUpperInvariant();
    
                var newNumber = new StringBuilder();
                foreach (var c in raw)
                {
                    if (" -0123456789".Contains(c))
                    {
                        newNumber.Append(c);
                    }
                    else 
                    {
                        var result = TranslateToNumber(c);
                        if (result != null)
                            newNumber.Append(result);
                    }
                    // otherwise we've skipped a non-numeric char
                }
                return newNumber.ToString();
            }
            static bool Contains (this string keyString, char c)
            {
                return keyString.IndexOf(c) >= 0;
            }
            static int? TranslateToNumber(char c)
            {
                if ("ABC".Contains(c))
                    return 2;
                else if ("DEF".Contains(c))
                    return 3;
                else if ("GHI".Contains(c))
                    return 4;
                else if ("JKL".Contains(c))
                    return 5;
                else if ("MNO".Contains(c))
                    return 6;
                else if ("PQRS".Contains(c))
                    return 7;
                else if ("TUV".Contains(c))
                    return 8;
                else if ("WXYZ".Contains(c))
                    return 9;
                return null;
            }
        }
    }

    Save the changes to the PhoneTranslator.cs file by clicking File > Save (or by pressing CTRL+S), then close the file.

  15. The next step is to add code to wire up the user interface by inserting backing code into the MainActivity class. Begin by wiring up the Translate button. In the MainActivity class, find the OnCreate method. The next step is to add the button code inside OnCreate, below the base.OnCreate(bundle) and SetContentView (Resource.Layout.Main) calls. First, modify the template code so that the OnCreate method resembles the following:

    using System;
    using Android.App;
    using Android.Content;
    using Android.Widget;
    using Android.OS;
    
    namespace Phoneword
    {
        [Activity (Label = "Phone Word", MainLauncher = true)]
        public class MainActivity : Activity
        {
            protected override void OnCreate (Bundle bundle)
            {
                base.OnCreate (bundle);
    
                // Set our view from the "main" layout resource
                SetContentView (Resource.Layout.Main);
    
                // New code will go here
            }
        }
    }
  16. Get a reference to the controls that were created in the layout file via the Android Designer. Add the following code inside the OnCreate method, after the call to SetContentView:

    // Get our UI controls from the loaded layout
    EditText phoneNumberText = FindViewById<EditText>(Resource.Id.PhoneNumberText);
    TextView translatedPhoneWord = FindViewById<TextView>(Resource.Id.TranslatedPhoneWord);
    Button translateButton = FindViewById<Button>(Resource.Id.TranslateButton);
  17. Add code that responds to user presses of the Translate button. Add the following code to the OnCreate method (after the lines added in the previous step):

    // Add code to translate number
    translateButton.Click += (sender, e) =>
    {
        // Translate user’s alphanumeric phone number to numeric
        string translatedNumber = Core.PhonewordTranslator.ToNumber(phoneNumberText.Text);
        if (string.IsNullOrWhiteSpace(translatedNumber))
        {
            translatedPhoneWord.Text = string.Empty;
        }
        else
        {
            translatedPhoneWord.Text = translatedNumber;
        }
    };
  18. Save your work by selecting File > Save All (or by pressing CTRL-SHIFT-S) and build the application by selecting Build > Rebuild Solution (or by pressing CTRL-SHIFT-B).

    If there are errors, go through the previous steps and correct any mistakes until the application builds successfully. If you get a build error such as, Resource does not exist in the current context, verify that the namespace name in MainActivity.cs matches the project name (Phoneword) and then completely rebuild the solution. If you still get build errors, verify that you have installed the latest Xamarin.Android updates.

  19. You should now have a working application – it's time to add the finishing touches! In MainActivity.cs, edit the Label for the MainActivity. The Label is what Android displays at the top of the screen to let users know where they are in the application. At the top of the MainActivity class, change the Label to Phone Word as shown here:

    namespace Phoneword
    {
        [Activity (Label = "Phone Word", MainLauncher = true)]
        public class MainActivity : Activity
        {
            ...
        }
    }
  20. Now it's time to set the application icon. By default, Visual Studio will provide a default icon for the project. Let's delete these files from the solution, and replace them with a different icon. Expand the Resources folder in the Solution Pad. Notice that there are five folders that are prefixed with mipmap-, and that each of these folders contains a single Icon.png file:

    mipmap- folders and Icon.png files

    It is necessary to delete each of these icon files from the project. Right click on each of Icon.png files, and select Delete from the context menu:

    Delete default Icon.png

    Click on the Delete button in the dialog.

  21. Next, download and unzip Xamarin App Icons set. This zip file holds the icons for the application. Each icon is visually identical but at different resolutions it renders correctly on different devices with different screen densities. The set of files must be copied into the Xamarin.Android project. In Visual Studio, in the Solution Explorer, right-click the mipmap-hdpi folder and select Add > Existing Items:

    Add files

  22. From the selection dialog, navigate to the unzipped Xamarin AdApp Icons directory and open the mipmap-hdpi folder. Select Icon.png and click Add.

  23. Repeat these steps for each of the mipmap- folders until the contents of the mipmap- Xamarin App Icons folders are copied to their counterpart mipmap- folders in the Phoneword project.

  24. After all the icons are copied to the Xamarin.Android project, open the Project Options dialog by right clicking on the project in the Solution Pad. Select Build > Android Application and select @mipmap/icon from the Application icon combo box:

    Setting the project icon

  25. Finally, test the application by running it on an Android device or emulator and translating a Phoneword:

    Screenshot of app when it is complete

  1. Launch Visual Studio for Mac from the Applications folder or from Spotlight.

  2. Click New Solution... to create a new project.

  3. In the Choose a template for your new project dialog, click Android > App and select the Android App template. Click Next.

    Choose the Android App template

  4. In the Configure your Android app dialog, name the new app Phoneword and click Next.

    Configure the Android App

    In the Configure your new Android App dialog, leave the Solution and Project names set to Phoneword and click Create to create the project. Be sure to uncheck the checkbox for Xamarin Test Cloud.

  5. After the new project is created, expand the Resources folder and then the layout folder in the Solution pad. Double-click Main.axml to open it in the Android Designer. This is the layout file for the screen when it is viewed in the Android Designer:

    Open Main.axml

  6. Select the Hello World, Click Me! Button on the design surface and press the Delete key to remove it.

  7. From the Toolbox (the area on the right), enter text into the search field and drag a Text (Large) widget onto the design surface (the area in the center):

    Add large text widget

  8. With the Text (Large) widget selected on the design surface, you can use the Properties pad to change the Text property of the Text (Large) widget to Enter a Phoneword: as shown below:

    Set large text widget properties

  9. Next, drag a Plain Text widget from the Toolbox to the design surface and place it underneath the Text (Large) widget. Notice that you can use the search field to help locate widgets by name:

    Add plain text widget

  10. With the Plain Text widget selected on the design surface, you can use the Properties pad to change the Id property of the Plain Text widget to @+id/PhoneNumberText and change the Text property to 1-855-XAMARIN:

    Set plain text widget properties

  11. Drag a Button from the Toolbox to the design surface and place it underneath the Plain Text widget:

    Add a button

  12. With the Button selected on the design surface, you can use the Properties pad to change the Id property of the Button to @+id/TranslateButton and change the Text property to Translate:

    Configure as the translate button

  13. Drag a TextView from the Toolbox to the design surface and place it under the Button widget. With the TextView selected, set the id property of the TextView to @+id/TranslatedPhoneWord and change the text to an empty string:

    Set the properties on the text view.

  14. Save your work by pressing ⌘ + S.

  15. Now, add some code to translate phone numbers from alphanumeric to numeric. Add a new file to the project by clicking the gear icon next to the Phoneword project in the Solution pad and choosing Add > New File...:

    Add a new file to the project

  16. In the New File dialog, select General > Empty Class, name the new file PhoneTranslator, and click New. This creates a new empty C# class for us.

  17. Remove all of the template code in the new class and replace it with the following code:

    using System.Text;
    using System;
    namespace Core
    {
        public static class PhonewordTranslator
        {
            public static string ToNumber(string raw)
            {
                if (string.IsNullOrWhiteSpace(raw))
                    return "";
                else
                    raw = raw.ToUpperInvariant();
    
                var newNumber = new StringBuilder();
                foreach (var c in raw)
                {
                    if (" -0123456789".Contains(c))
                    {
                        newNumber.Append(c);
                    }
                    else 
                    {
                        var result = TranslateToNumber(c);
                        if (result != null)
                            newNumber.Append(result);
                    }
                    // otherwise we've skipped a non-numeric char
                }
                return newNumber.ToString();
            }
            static bool Contains (this string keyString, char c)
            {
                return keyString.IndexOf(c) >= 0;
            }
            static int? TranslateToNumber(char c)
            {
                if ("ABC".Contains(c))
                    return 2;
                else if ("DEF".Contains(c))
                    return 3;
                else if ("GHI".Contains(c))
                    return 4;
                else if ("JKL".Contains(c))
                    return 5;
                else if ("MNO".Contains(c))
                    return 6;
                else if ("PQRS".Contains(c))
                    return 7;
                else if ("TUV".Contains(c))
                    return 8;
                else if ("WXYZ".Contains(c))
                    return 9;
                return null;
            }
        }
    }

    Save the changes to the PhoneTranslator.cs file by choosing File > Save (or by pressing ⌘ + S), then close the file. Ensure that there are no compile-time errors by rebuilding the solution.

  18. The next step is to add code to wire up the user interface by adding the backing code into the MainActivity class. Double-click MainActivity.cs in the Solution Pad to open it.

  19. Begin by adding an event handler to the Translate button. In the MainActivity class, find the OnCreate method. Add the button code inside OnCreate, below the base.OnCreate(bundle) and SetContentView (Resource.Layout.Main) calls. Remove the template button handling code so that the OnCreate method resembles the following:

    using System;
    using Android.App;
    using Android.Content;
    using Android.Runtime;
    using Android.Views;
    using Android.Widget;
    using Android.OS;
    
    namespace Phoneword
    {
        [Activity (Label = "Phone Word", MainLauncher = true)]
        public class MainActivity : Activity
        {
            protected override void OnCreate (Bundle bundle)
            {
                base.OnCreate (bundle);
    
                // Set our view from the "main" layout resource
                SetContentView (Resource.Layout.Main);
    
                // Our code will go here
            }
        }
    }
  20. Next, a reference is needed to the controls that were created in the layout file with the Android Designer. Add the following code inside the OnCreate method (after the call to SetContentView):

    // Get our UI controls from the loaded layout
    EditText phoneNumberText = FindViewById<EditText>(Resource.Id.PhoneNumberText);
    TextView translatedPhoneWord = FindViewById<TextView>(Resource.Id.TranslatedPhoneWord);
    Button translateButton = FindViewById<Button>(Resource.Id.TranslateButton);
  21. Add code that responds to user presses of the Translate button by adding the following code to the OnCreate method (after the lines added in the last step):

    // Add code to translate number
    string translatedNumber = string.Empty;
    
    translateButton.Click += (sender, e) =>
    {
        // Translate user’s alphanumeric phone number to numeric
        translatedNumber = PhonewordTranslator.ToNumber(phoneNumberText.Text);
        if (string.IsNullOrWhiteSpace(translatedNumber))
        {
            translatedPhoneWord.Text = string.Empty;
        }
        else
        {
            translatedPhoneWord.Text = translatedNumber;
        }
    };
  22. Save your work and build the application by selecting Build > Build All (or by pressing ⌘ + B). If the application compiles, you will get a success message at the top of Visual Studio for Mac:

    If there are errors, go through the previous steps and correct any mistakes until the application builds successfully. If you get a build error such as, Resource does not exist in the current context, verify that the namespace name in MainActivity.cs matches the project name (Phoneword) and then completely rebuild the solution. If you still get build errors, verify that you have installed the latest Xamarin.Android and Visual Studio for Mac updates.

  23. Now that you have a working application, it's time to add the finishing touches! Start by editing the Label for MainActivity. The Label is what Android displays at the top of the screen to let users know where they are in the application. At the top of the MainActivity class, change the Label to Phone Word as shown here:

    namespace Phoneword
    {
        [Activity (Label = "Phone Word", MainLauncher = true)]
        public class MainActivity : Activity
        {
            ...
        }
    }
  24. Now it's time to set the application icon. By default, Visual Studio for Mac will provide a default icon for the project. Let's delete these files from the solution, and replace them with a different icon. Expand the Resources folder in the Solution Pad. Notice that there are five folders that are prefixed with mipmap-, and that each of these folders contains a single Icon.png file:

    mipmap- folders and Icon.png files

    It is necessary to delete each of these icon files from the project. Right click on each of Icon.png files, and select Remove from the context menu:

    Delete default Icon.png

    Click on the Delete button in the dialog.

  25. Next, download and unzip Xamarin App Icons set. This zip file holds the icons for the application. Each icon is visually identical but at different resolutions it renders correctly on different devices with different screen densities. The set of files must be copied into the Xamarin.Android project. In Visual Studio for Mac, in the Solution Pad, right-click the mipmap-hdpi folder and select Add > Add Files:

    Add files

  26. From the selection dialog, navigate to the unzipped Xamarin AdApp Icons directory and open the mipmap-hdpi folder. Select Icon.png and click Open.

  27. In the Add File to Folder dialog box, select Copy the file into the directory and click OK:

    Copy the file to the directory dialog

  28. Repeat these steps for each of the mipmap- folders until the contents of the mipmap- Xamarin App Icons folders are copied to their counterpart mipmap- folders in the Phoneword project.

  29. After all the icons are copied to the Xamarin.Android project, open the Project Options dialog by right clicking on the project in the Solution Pad. Select Build > Android Application and select @mipmap/icon from the Application icon combo box:

    Setting the project icon

  30. Finally, test the application by running it on an Android device or emulator and translating a Phoneword:

    Screenshot of app when it is complete

Congratulations on completing your first Xamarin.Android application! Now it's time to dissect the tools and skills you have just learned. Next up is the Hello, Android Deep Dive.

Xamarin Workbook

If it's not already installed, install the Xamarin Workbooks app first. The workbook file should download automatically, but if it doesn't, just click to start the workbook download manually.