Android Xamarin Binding
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This document discusses Xamarin Android binding, which allows C# applications to use existing Java libraries for Android. It explains that binding generates managed callable wrappers (MCWs) that encapsulate Java Native Interface (JNI) calls so client code does not need to know the underlying complexity. The process of creating bindings for a Xamarin project involves adding a Java JAR file to a binding project, which generates C# wrappers in a DLL. Transform files like api.xml, EnumFields.xml, and Metadata.xml map the Java classes and members to .NET.
![Metadata.xml
<attr
path="/api/package[@name='com.kontakt.sdk.android.common.model']/interface[@name='IModel']“
name="visibility">public</attr>
<remove-node
path="/api/package[@name='com.kontakt.sdk.android.common.util']/class[@name='Closeables']/me
thod[@name='closeQuietly' and count(parameter)=1 and
parameter[1][@type='java.io.OutputStream']]" />](https://image.slidesharecdn.com/androidbinding-151024212145-lva1-app6891/85/Android-Xamarin-Binding-20-320.jpg)
Android Xamarin Binding
- 1. Xamarin Android Binding David Hauck Software Engineer at Skyline Technologies Xamarin Certified Developer
- 2. Principal Sponsor http://www.SkylineTechnologies.com Thank our Principal Sponsor by tweeting and following @SkylineTweets Milwaukee Code Camp 2015
- 3. Silver Sponsors Gold Sponsors Milwaukee Code Camp 2015
- 4. August 8th – 10th 2016 Kalahari Resort, Wisconsin Dells http://www.ThatConference.com
- 5. What is binding? Run an existing Java library in your C# application
- 6. Why should we use binding? Many existing java libraries for Android Use them in your app with little effort
- 7. How does binding work? Picture from xamarin.com https://developer.xamarin.com/guides/android/advanced_topics/java_integration_overview/binding-a-java-library/
- 8. Managed Callable Wrapper (MCW) Java Class C# Code
- 9. Why MCWs? Encapsulate JNI use so that client code doesn't need to know about the underlying complexity Permit sub-classing Java types and implementing Java interfaces
- 10. Under the hood JNI The Java Native Interface (JNI) is a programming framework that enables Java code running in a Java Virtual Machine (JVM) to call and be called by native applications (programs specific to a hardware and operating system platform) and libraries written in other languages such as C, C++ and assembly. (Wikipedia)
- 11. Example: Constructor Binding int value = 42; IntPtr class_ref = JNIEnv.FindClass ("java/lang/Integer"); IntPtr id_ctor_I = JNIEnv.GetMethodID (class_ref, "<init>", "(I)V"); IntPtr lrefInstance = JNIEnv.NewObject (class_ref, id_ctor_I, new JValue (value)); // Dispose of lrefInstance, class_ref…
- 12. Creating MCWs for your Xamarin project Have a java library (jar) Create a Xamarin Binding project Insert jar into project Build the project Creates dll consisting of the MCW
- 13. Jar Build Actions Input Jar Will create the actual bindings for this jar EmbeddedReferenceJar
- 14. Creating MCWs for your Xamarin project api.xml Transforms MCW
- 15. Api.xml {Project_Directory}objDebugapi.xml Xamarin parses the jar and creates this file Diagram of how the api is laid out Includes classes, methods, etc
- 16. Api.xml
- 17. Transforms EnumFields.xml Converts Constants to Enums EnumMethods.xml Changes parameters in methods to use Enums Metadata.xml Various add/remove/edit transforms
- 18. EnumFields.xml <mapping jni-class="android/support/v4/app/FragmentActivity$FragmentTag" clr-enum-type="Android.Support.V4.App.FragmentTagType"> <field jni-name="Fragment_name" clr-name="Name" value="0" /> <field jni-name="Fragment_id" clr-name="Id" value="1" /> <field jni-name="Fragment_tag" clr-name="Tag" value="2" /> </mapping>
- 19. EnumMethods.xml <mapping jni-class="android/support/v4/app/Fragment.SavedState"> <method jni-name="writeToParcel" parameter="flags" clr-enum- type="Android.OS.ParcelableWriteFlags" /> </mapping>
- 20. Metadata.xml <attr path="/api/package[@name='com.kontakt.sdk.android.common.model']/interface[@name='IModel']“ name="visibility">public</attr> <remove-node path="/api/package[@name='com.kontakt.sdk.android.common.util']/class[@name='Closeables']/me thod[@name='closeQuietly' and count(parameter)=1 and parameter[1][@type='java.io.OutputStream']]" />
- 21. Demo
Editor's Notes
- #8: Manage Callable Wrappers Android Callable Wrappers