Android Callable Wrappers (ACWs) are a crucial component in Xamarin.Android that facilitate the interaction between managed code (C#) and the Android runtime. They are automatically generated by the monodroid.exe program during the build process for any types that inherit from Java.Lang.Object either directly or indirectly[1][11].
Key Points about ACWs:
Purpose:
ACWs are required whenever the Android runtime needs to invoke managed code. This is necessary because the Android Runtime (ART) does not support runtime class registration, specifically the JNI function DefineClass()[1][10].
Functionality:
ACWs act as Java proxies for managed types. They ensure that calls from Java code to managed code are correctly routed. This involves creating Java classes that mirror the managed classes, including constructors and overridden methods[1][11].
Naming:
The names of ACWs are based on the MD5 hash of the fully qualified name of the managed type. This naming convention helps avoid conflicts when the same type name is used in different assemblies[1].
Generation:
During the build process, monodroid.exe scans for all types that inherit from Java.Lang.Object and generates the corresponding ACWs. These wrappers include the necessary Java code to interface with the managed code[1][11].
Usage:
ACWs are essential for scenarios where managed code needs to override virtual methods or implement interfaces defined in Java. They ensure that these methods are callable from the Java side, maintaining the integrity of the method calls across the managed and unmanaged boundaries[1][10].
Example Scenario:
When a Xamarin.Android application needs to override a method from an Android class, such as Activity.OnCreate, an ACW is generated to handle the method call from the Android runtime to the managed implementation in C#. This allows the Xamarin.Android application to seamlessly integrate with the Android platform while using C# as the programming language[1][11].
In summary, Android Callable Wrappers are a vital mechanism...
