Android lacks tasks to generate sourceJars, javaDocJars by default.
Wiebe posted a neat solution, I improved upon it and uploaded it as a Gist:
This should work equally good if you replace .libraryVariants with .applicationVariants but I don´t know why you want to generate Javadoc for an App.
This will create these tasks:
Jar tasks
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generateDebugJavadocJar - Assembles a jar archive containing the generated Javadoc API documentation of debug.
generateDebugProguardFilesJar - Assembles a jar archive containing the Proguard files of debug.
generateDebugSourcesJar - Assembles a jar archive containing the main sources of debug.
generateJavadoc - Generate all Javadoc of all Variants
generateJavadocJar - Generate all Javadoc Jars of all Variants
generateMinifiedJavadocJar - Assembles a jar archive containing the generated Javadoc API documentation of minified.
generateMinifiedProguardFilesJar - Assembles a jar archive containing the Proguard files of minified.
generateMinifiedSourcesJar - Assembles a jar archive containing the main sources of minified.
generateProguardJar - Generate all Proguard Jars of all Variants
generateReleaseJavadocJar - Assembles a jar archive containing the generated Javadoc API documentation of release.
generateReleaseProguardFilesJar - Assembles a jar archive containing the Proguard files of release.
generateReleaseSourcesJar - Assembles a jar archive containing the main sources of release.
generateSourcesJar - Generate all Sources Jars of all Variants
If you have comments on the solution, feel free add them directly in the Gist, fork it, improve it!