Kotlin interop with Java
This repo shows an example on how to manage interop between Kotlin and Java, in the particular case of a partial conversion of a project that uses ButterKnife from Java to Kotlin.
For more information see this blog post.
This repo has for branches:
- master: original code, only Java
- kotlin-annotationprocessor: second activity converted to Kotlin, still using
annotationProcessor. Compiles, but injection fails.
- kotlin-annotationprocessor-kapt: second activity converted to Kotlin, using both
kapt. Compilation fails with "Error:@BindView fields must not be private or static." I've also seen a "Error:Execution failed for task ':app:compileDebugJavaWithJavac'. kotlin.jvm.internal.FunctionReference.(ILjava/lang/Object;)V" in some cases. See the following Stack Overflow question: Project won't build with Kotlin 1.1.3.
- kotlin-kapt: second activity converted to Kotlin, using only
kapt. Same issue.
- kotlin-workaround: second activity converted to Kotlin, using only
kapt3. Uses a
@JvmField()to workaround the problem of ButterKnife not injecting the Kotlin activity. Notice the usage of
kapt3by applying the
kotlin-kaptplugin to Gradle script.
Important: make sure to clean the build after aplying the workaround, as sometimes generated code is left and produces errors during compilation.
Notice that there are two small, Espresso tests that check if injection has been successful in each activity. Also, the message at the bottom of each activity shows you whether the injection succeeded or not.
Copyright (c) 2017 Xavier Rubio Jansana
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