Mono For Android 4.2


Visual Studio Users: You should be prompted with this update when you open a MfA project. You can also check manually in Tools > Options > Mono for Android.

MonoDevelop Users: You should be prompted to upgrade next time you open MonoDevelop, or you can use Help > Check for Updates. IDE support requires MonoDevelop 3.0.

Companion Documentation

Documentation for major components of this release can be found in these articles:

  • Binding a Java Library - Describes how to use the new Java Library Binding project to create a Managed Callable Wrapper (Binding) for arbitray java libraries (jars).
  • API Metadata Reference - Companion documentation to the Binding a Java Library doc, this doc covers binding transformation file syntax.
  • Fragments Walkthrough - Describes how to use fragments to reuse controls across different form factors. Also covers Android Compatibility Libraries to support fragments on older OS versions.

Changes since 4.0.6

Visual Studio Integration Enhancements

  • NOTE: If you are opening an existing MfA solution, you may need to set it to Deploy in Build > Configuration Manager.*

Layout Designer

We are extremely pleased to introduce our graphical designer for producing Android layout files. This should make designing views for applications much easier.

Device Toolbar

There is now a toolbar available that provides a dropdown list of all running emulators and attached devices. This allows you to quickly set your default device and avoid being prompted to choose your device for every run.

The toolbar will remember your choice even if the device isn't available. For example, you can set it to your phone, and it will switch to your phone every time your phone is attached.

Choosing " -- Prompt for Device --" will utilize the current behavior of prompting you on each run.

Non-modal Deployment

Deploying to an emulator/device no longer blocks your work. Deployment is now done in the background, with updates displayed in the status bar. Deployment can be cancelled via Build->Cancel, and should now cancel immediately if requested.

Which projects will be deployed follows the same model as Windows Phone 7, and can be configured via the Deploy checkbox in Build -> Configuration Manager.

Integrated Logcat

When running in Debug mode, Visual Studio will now automatically attach to the device's logcat and display the results in the Output pane. Many types of logging and exceptions may only show up in logcat. Now they appear automatically instead of being another place to remember to check.

Other Improvements

  • Additional parameters can be passed to emaulators started in Visual Studio: - Tools > Options > Mono for Android > Additional Emulator Launch Arguments

  • Project templates for Honeycomb/Ice Cream Sandwich applications.

  • Item template for a Fragment file.

MonoDevelop Improvements

Layout Designer

MonoDevelop 3.0 also includes our graphical designer for producing Android layout files.

Other Improvements

  • Project templates for Honeycomb/Ice Cream Sandwich applications.
  • Item template for a Fragment file.
  • MonoDevelop got "Publish Android Application" signing wizard that lets you sign the application package ( .apk ) and get ready to publish to Google Play (formerly Android Market).

Java Binding Library project and tool

In this release we introduced a new library generator tool that makes it possible to bind existing Android Java library ( .jar) to C# assembly ( .dll). Now you can consume external Java library from managed code.

This includes support for importing Android Library Project into managed library, either via local library project description files ( or archived bin files ( .zip).

These new features are available in Visual Studio or MonoDevelop as a new project type ( Java Bindings Library project).

Java Binding Library tutorial

Smaller Shared Runtime

The shared runtime needed is now about 50% smaller. This was accomplished by splitting each architecture into it's own runtime and removing debug symbols for Mono and the BCL. (Debug symbols for * your* code are still used.) If you have a situation where debug symbols for Mono help you, remove any existing shared runtime from your device, and turn on " Provide shared runtime debug symbols" from Tools > Options > Mono for Android. Then re-deploy and full debug symbols will be available.

x86 emulator support

x86 emulators are now fuly supported in the trial and full MfA editions. This release includes fixes for library loading errors with logcat messages such as java.lang.UnsatisfiedLinkError: Cannot load library: reloc_library[1311]: 799 cannot locate 'atexit'..."

More event listener methods are bound to events

Previously, event listener methods would only be mapped to events if the event listener interface contained only one method. We now support event listener interfaces that have more than one method, generating one event per event listener interface method.

Improved API level support

Historically, Applications (and Debug Platform packages) would target a "minimum" API level, and could only be installed on targets running that API level or later. For example, if an Application was built against Android v2.3 (API level 10), it couldn't reliably run on a lower API level (e.g. API level 8) (" the MotionEvent problem").

This has been fixed so that it is now possible to sanely target an API level that is higher than the target's API level (e.g. target API 14 and run on API 8). Care must still be taken to only use types and members that exist on the target.

Earlier error checking

Build steps that used to be done at package creation time are now done as part of the normal build process, allowing errors to be flagged earlier. This includes Android Callable Wrapper generation and linking.

API Improvements

API Level 15 support

This release contains support for API Level 15 (updated Ice Cream Sandwich API).

Almost complete enum migration

Our API conversion from classic int constants to decent enum has always been incomplete and changes were based on feedback. This time we took time to review the entire API and introduced a lot of new enums, as well as fixed method parameters and return values from int to enum.

Since this brings a lot of API breakage, we also introduced some transitive fields whose name match the old int-based fields (with [Obsoleted]) for easier application upgrades.

Android Compatibility Library binding

As we have received many requests for this, this release contains bindings for Android compatibility library that brings Fragments, ViewPager and many other useful stuff from Honeycomb to old Android platform.

Exporting arbitrary Java member for better Java integration

It is now easier to export methods for invocation and fields for access by Java. The new Mono.Android.Export.dll assembly allows using the new [Export] custom attribute so that methods will be declared on the generated Android Callable Wrapper, and the new [ExportField] custom attribute allows fields to be declared in the generated Android Callable Wrapper.

These remove a couple of limitations in Mono for Android limitations:

  • You can implement Java.IO.ISerializable interface in managed code, as it is possible to give readObject and writeObject names in Java (Android Callable Wrapper) code.
  • You can implement Android.OS.IParcelable interface in managed code, as it is possible to export CREATOR field explicitly.
  • You can use android:onClick attribute to pass a Java method name as a click handler, as it is possible to export arbitrary managed method in Java code, unlike non-export methods which are unavailable to Java.

Dynamic support

In this release, we added DLR support which also enables C# 4.0 dynamic support. System.Core.dll is expanded to include them, and Microsoft.CSharp.dll and Mono.CSharp.dll joined the framework assemblies party.

(Note that there is some limitation on using dynamic types to interoperate with Java code and the underlying dalvik runtime.)

Instrumentation support

In this release, we changed the bootstrap hook to initialize mono runtime to support Instrumentation aside from existing ordinal applications. This means now you can write your Instrumentation and start it from adb shell commands.

Java annotations and managed attributes

This release supports generating managed attributes from Java annotations. For example, we create Java.Lang.DeprecatedAttribute from java.lang.Deprecated annotation type. This is achieved by new AnnotationAttribute (Java.Lang.DeprecatedAttribute class has this managed attrubute).

When these annotation attributes were used in managed code, our build process generates corresponding Java annotation in the Java code (Android Callable Wrapper).

.NET names can now be used in Resource XML

In previous releases, when writing a Resource XML file that referenced a managed class, the Java name of the Android Callable Wrapper had to be used. For example, the GLCube Resources\Layout\main.xml file uses the <mono.samples.glcube.PaintingView/> element to refer to the Mono.Samples.GLCube.PaingintView type. Starting in this release, the fully-qualified managed name can be used, resulting in <Mono.Samples.GLCube.PaintingView/>. Android v4.0 Fragments may also use the fully-qualified managed name instead of the Android Callable Wrapper Java name.

API Changes

Breaking Changes

  • IJavaObject now implements IDisposable .
  • Various ToJniHandle() methods have been renamed to ToLocalJniHandle() , and now always return a JNI local reference.
  • int to enum changes
  • Due to the event listener change, we had to replace ItemEventArgs which was used in some limited classes with AdapterView.ItemClickEventArgs which is used everywhere applicable. ItemEventArgs still exists, but since event signature has changed, your delegate methods need to be changed as well. Use of type-inferred lambda delegates should not be effected by this change.
  • Various int to Color changes on properties, method return types, and constructor and method parameters.
  • The various <em>Foo</em>EventArgs.E properties are now named <em>Foo</em>EventArgs.Event .
  • The various <em>Foo</em>EventArgs.V properties have been removed, and their value is now the sender parameter of the EventHandler delegate.
  • Rename ViewAttachedToWindowEventArgs.V to ViewAttachedToWindowEventArgs.AttachedView and ViewDetachedFromWindowEventArgs.V to ViewDetachedFromWindowEventArgs.DetachedView .
  • RemoteViews.SetViewVisibility() now takes ViewStates enum, not SystemUiFlags enum.
  • Use of SimpleAdapter and SimpleExpandableListAdapter will need to change to use JavaList and JavaDictionary instead of List and Dictionary . This change is necessitated by the object identify fix in bug 2147 . See also the mailing list threads: - Mono for Android 4.2.1 SimpleExpandableListAdapter problems
  • SimpleAdapter Break in 4.2.1

Bug Fixes

  • Java library binding assemblies will now register the Java package to C# type mapping during process startup. This allows Activity.FindViewById(int) to e.g. return a MapView instead of a ViewGroupInvoker .
  • GC fixes: TODO description regarding null handle check in libmonodroid, removal of JLO fields from Framework Peers
  • Better gref behavior when using foreach over Android.Runtime.JavaList and related collection types.
  • Android.App.Application.SynchronizationContext is now thread-aware, so that it won't deadlock when trying to Send() a message when already on the UI thread.
  • Android Callable Wrappers no longer emit @Override . This is to avoid the unmitigated evil that is declaring a custom Override annotation . (Granted, [Export] is a much better fix, but there's not any actual need for @Override in the Android Callable Wrappers...)
  • Java.Lang.Object coercion operators now null-check their parameters, so implicitly converting a null System.String to a Java.Lang.Object now returns null instead of throwing an exception.
  • Application startup now performs a zipalign check to ensure that zipalign was run before installing the .apk. This helps reduce a source of really bizarre and obscure errors due to unaligned assemblies.
  • System.Data.Services.Client now contains string resources. Exception messages should actually be useful now.
  • NTLM authentication fixes: set the correct flags when the domain is not set. Allow domain\user and domain/user as the user name and set domain and user accordingly.
  • Fix Java.Lang.Object deserialization for JSON in Release builds.
  • Duplicate <uses-library/> elements within AndroidManifest.xml are removed.
  • Emit <uses-sdk/> before <application/> within AndroidManifest.xml. (Failure to do so results in Android ignoring themes.)
  • The Java.Lang.Throwable.StackTrace property no longer returns null .
  • We now validate at build-time that the package name contains a period ( '.' ). If the package name doesn't contain a period, then Android will give a INSTALL_FAILED_INVALID_APK when installing the package.
  • Mono for Android assemblies are now strong-named.
  • Building a Release build twice in a row no longer generates javac errors.
  • Unsubscribing from an event will now remove the Java-side Listener implementation, reducing gref count. Previously the entire object graph would need to be collectable and a full GC would be required to collect the Listener implementation. Mailing list reference .
  • 210 : Fixup package names so that Android will accept them
  • 374 : Paint.Color should be of type Android.Graphics.Color , not int .
  • 382 : Add [Export] support to mandroid.
  • 638 : invalid format string when loading into a datatable records from the sqlite db where they have datetime fields with null values.
  • 645: : MfA should allow missing library at build/run steps.
  • 795 : System.MethodAccessException when creating generic class.
  • 981 : sbyte.Parse, short.Parse raise OverflowException when parsing hexadecimal negative numbers.
  • 1164 : TargetInvocationException / SerializationException on response from a web service (which works on MonoTouch).
  • 1416 : Linker in 1.9.1 removing override methods?
  • 1437 : WCF FaultException<TDetail> support missing.
  • 2147 : Android.Runtime.JavaObject instances should no longer be returned to developer code. It should be automatically "unwrapped" to provide the original instance.
  • 2190 : sdb interrupt code not signal safe.
  • 2191 : SqliteDataReader throws on GetDecimal()
  • 2347 : The ArrayAdapter<T>(..., T[]) constructors do not support value types.
  • 2422 : OpenTK.FrameEventArgs.set_Time crash
  • 2483 : Calling CancelAsync when using DownloadDataAsync causes System.Threading.ThreadInterruptedException: Thread interrupted
  • 2769 : System.Core does not include Task.Unwrap()
  • 2775 : Debugger tooltips for DateTimes are corrupted
  • 2843 : WCF: SerializationException when processing response that contains a nullable enum
  • 2859 : WCF: SerializationException trying to process FaultException
  • 2926 : DataTable.ImportRow causes InvalidCastException
  • 2936 : DateTime.FromFileTimeUTC has incorrect Kind set
  • 3100 : Error With System.Net.WebClient.UploadProgressChanged Event
  • 3137 : german country code creates a floating-point number problem
  • 3476 : culture-data return wrong values
  • 3479 : All linked assemblies need to check for IJavaObject
  • 3497: : Package building step uses excessive memory that then is not GCed
  • 3500: : Bindings generator crashes on Parse .jar
  • 3634 : XElement with decimal date get formatted has wrong ToString representation
  • 3641 : Mono 2.11 make check failures on Cygwin
  • 3827 : SortedSet missing from System.dll
  • 3876 : HttpWebRequest chunked reading problem
  • 3894 : Async HttpWebRequest with NTLM authentication does not auto redirect when a 301/303 response received
  • 4040: : System.ArgumentException when inheriting AsyncTask<,,> and overriding RunInBackground but not DoInBackground
  • 4441 : Compatibility library should be called Support Packages
  • 4485 : Java Binding Library generates C# code that does not build
  • 4571 : .jar library binding doesn't work with GoogleAdMobAdsSdk-6.0.0.jar .
  • 4592 : [Export] + Release builds == TargetInvocationException
  • 4592 : Preserve FromJniHandle() , ToLocalJniHandle() methods in Release builds.
  • 4594 : API Demo exception thrown on Graphics->Alpha Bitmap on Release configuration
  • 4605 : Android.Widget.RemoteViews.SetViewVisibility does not exist for all API versions
  • 4783 : Check types when marshaling arrays.
  • 4821 : Support marshaling arrays of enum types.
  • 4822 : ResolveLibraryProjectImports can't find assembly via HintPath .


Warning: Samsung shipped a broken kernel with Android 2.1, which is not able to support JIT compilation. If you possess a Galaxy-class device with Android 2.1, you will get unexpected results, this is caused by a kernel bug that breaks cache coherency, rendering any engine doing JIT compilation useless. Check with your manufacturer/carrier for an Android 2.2 update.

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