ActionBarSherlock + Xamarin + MVVMCross

 

Short history of ActionBar in Android and Xamarin

1. ActionBar was first added in Android 3.0 (API Level 11).

2. ActionBarSherlock is a third-party library created by Jake Wharton, which brought ActionBar support for Android 2.x: “The library will automatically use the native action bar when appropriate or will automatically wrap a custom implementation around your layouts. This allows you to easily develop an application with an action bar for every version of Android from 2.x and up.”

ActionBarSherlock it’s not just about ActionBar support on Android 2.x, it also has some nice features not available in the Android’s ActionBar implementation.

3. In July 2013, Android Support Library revision 18 introduced a new v7 appcompat library which has ActionBar support for Android 2.1+.

4. Xamarin created a free component for their store as a binding for the ActionBarSherlock, called ‘ActionBarSherlock for Xamarin’.

5. Xamarin created a free component for the Android support Library v7 (rev 18) http://components.xamarin.com/view/xamandroidsupportv7appcompat

I haven’t yet tried how the ActionBar works using the this support library.

 

Using ActionBar in Xamarin application with ActionBarSherlock Xamarin component

The steps are:

1. Create an Android application and add MvvmCross by NuGet. (MvvmCross creates and adds a FirstView activity to the project).

2. Add ActionBarSherlock for Xamarin component from Xamarin Components store

3. Make sure the Android project has ‘Compile using Android version’ and ‘Target Android version’ set to the latest Android version.

4. Add reference to Mono.Android.Support.v4

5. Add a MvvmCross implementation for SherlockFragmentActivity (MvxSherlockFragmentActivity).

   I create a folder ‘MvxSherlockActionBar’ in the Droid project and add to it these two files: MvxEventSourceSherlockFragmentActivity.cs MvxSherlockFragmentActivity.cs These add support for MvvmCross to SherlockActionBar.

6. Change the FirstView’s class parent from MvxActivity to MvxSherlockFragmentActivity and set the ActionBar’s theme

[Activity(Label = "View for FirstViewModel"] 
public class FirstView : MvxSherlockFragmentActivity
{
    protected override void OnCreate(Bundle bundle)
    {
        SetTheme(Resource.Style.Theme_Sherlock);
        base.OnCreate(bundle);
        SetContentView(Resource.Layout.FirstView);
    }
}

You should use SherlockFragmentActivity::SupportActionBar property to use the ActionBar.

A very basic walkthrough to the Xamarin component: http://components.xamarin.com/gettingstarted/XamarinActionBarSherlock 
Xamarin also created a sample application using Xamarin ActionBarSherlock component and made its source code available https://github.com/xamarin/monodroid-samples/tree/master/ActionBarSherlock It contains different examples of usage.

ActionBarSherlock in Xamarin Android targeting Android 2.1

ActionBarSherlock is a library which is an extension of the ActionBar in Android. ActionBar appeared in Android 4.

Besides being an extension, this library works for version previous to Android 4, starting from Android 2.1

 

First, we need to build the ActionBarSherlock from scratch using Eclipse. (I had also to install ‘Android SDK Tools’ using the Android SDK Manger).

Second, we need to create a Xamarin Java Binding Library, which will create a bridge library for Xamarin based on the ActionBarSherlock Android library.

For these two steps, follow instructions from http://www.craigsprogramming.com/2012/07/actionbarsherlock-with-mono-for-android.html

To test the app, in the app’s Activit1, just use the sample  code also posted there (use the code from TabActivity class).

 

In order to target Android 2.1:

1. Change properties of the ActionBarSherlockBindings project to have Android minimum version 2.1

2. For the app, also change properties to have Android minimum version 2.1 (in Visual Studio, right click on project, Properties and from the dialog, it’s in the Application tab, ‘Minimum Android to target’)

3. On the app, we need to change it to target Android 4. This is specified in the AndroidManifest.xml file of the app

If it does not exist, in Visual Studio, go to the app properties, and click on ‘Android Manifest’ Tab and click to generate the file.

Once done, UI appears with options for the manifest,  set ‘Target API level’ to 14.

 

Also,  once I targeted Android 2.1, I had to make few changes in the sample code for it to work.

Some classes need to be replaced with classes from the Android.Support.V4.App (like Fragment) and a constant (ActionBar.NavigationModeTabs instead of ActionBar_Sherlock.ActionBarSherlock.ActionBarNavigationMode.Tabs)

Now the app can be tested on an Android 2.1 device or emulator.