APIs & Javadoc

In this section we take a brief look at APIs supported by RoboVM.

NOTE: To find out which Java and iOS APIs are supported, check out the Javadocs for the RoboVM version you are using.

Class library

RoboVM's class library is composed of two parts:

  1. A JVM class library, based on Android
  2. Bindings for all iOS APIs via Bro

We only use the non-Android parts from Android's class library. This means the following packages are not supported:

  • android.*
  • com.android.*
  • dalvik.*
  • javax.microedition.khronos.*

NOTE: RoboVM does NOT support any Android-specific APIs on iOS. This includes APIs for UIs or background services.

On top of those runtime classes, we also expose all iOS APIs as idiomatic Java bindings. These are the APIs you use to write your user interfaces, access system services and so on. Our binding mechanism called Bro is similar to JNA, but integrates directly with Objective-C (including protocols and classes) and does not incur a performance overhead.

You can cross-reference the Java API for an iOS framework with its corresponding documentation on Apple's Developer Site. E.g. if you want to know about the internals of the UIButton class, head over to the Apple Developer Site and search for the class name to get its Objective-C API documentation. You can then search for Java method names within that site and match them with the corresponding Objective-C method name.

Third Party Library Support

RoboVM lets you exploit almost all of the Java ecosystem, including third party libraries you can find on Maven Central or other repositories. However, you need to be aware of some pitfalls and limitations that apply.

NOTE: As a general rule of thumb, if a third party library works on Android and does not depend on Android APIs, it will work on RoboVM.

Byte Code Loading

If a third party library uses runtime byte code loading/manipulation, it will not work with RoboVM. This is due to RoboVM being an ahead-of-time compiler. This means that all byte code that gets executed by your app needs to be known at compile time, so RoboVM can compile it to native machine code. RoboVM can not do this at runtime, due to restrictions imposed by Apple's App Store Terms of Service.

Many libraries let you configure whether byte code manipulation should be performed at compile time or at runtime. For RoboVM, you will have to use the compile time settings of such apps.

Reflection

Third party libraries such as ORMs or dependency injection frameworks make use of reflection a lot. RoboVM supports full reflection (minus loading byte code at runtime). For RoboVM to be able to load a class at runtime via reflection, it needs to know that this class is used by your application. RoboVM determines this by recursively gathering all the classes referenced by your app, starting with your app's main() method.

If a class is not directly referenced via code, but only via reflection, RoboVM will not compile it into your app. Trying to load such a class via reflection at runtime will thus result in an error.

You can explicitly specify classes or entire packages that RoboVM should compile into your application, even if they are not explicitly referenced. You can use the <forceLinkClasses> tag in your robovm.xml file to achieve this. See the configuration reference for more details.

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