Dagger and Kotlin. Dagger doesn't generate component classes

问题

I'm new with kotlin and Dagger. I have a little problem that I do not how to solve and I don't find a solution.

So this is what I have:

@Module
class AppModule (app: Application) {
    private var application: Application;

    init {
        this.application = app;
    }

    @Provides fun provideApplication(): Application? {
        return application;
    }

    @Provides fun provideResources(): Resources? {
        return application.resources;
    }
}

@Singleton
@Component(modules =  arrayOf(AppModule::class))
interface AppComponent: AppComponentBase {

    public class Initializer {
        private constructor(){}

        companion object {
            fun Init(app: Application): AppComponent? {
                return DaggerAppComponent.builder().appModule(AppModule(app)).build()
            }
        }
    }
}

AppComponentBase: This interface contain all the methods needed by this component.

Now, the problem is that this DaggerAppComponent class is not generated by Dagger if I do this DaggerAppComponent.builder().appModule(AppModule(app)).build() invocation within the companion object. If a invoke the same line any were by the companion object dagger generate de class without any problem.

An other thing I did look for a solution was create an other different class with the same structure, and importe the DaggerAppComponent as internal object, and I the same result happened.

I don't what to have the initialization of the component outside. So, there any other alternative solution, or what am I doing wrong?.

回答1:

You need to have the kapt processor in build.gradle:

kapt {
    generateStubs = true
}

dependencies {
    ...
    compile "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    compile 'com.google.dagger:dagger:2.0.2'
    kapt 'com.google.dagger:dagger-compiler:2.0.2'
    ...
}

This extension will generate the code for dagger.

Additionally, for newer gradle versions, you can also apply the plugin in your build.gradle:

apply plugin: 'kotlin-kapt'

dependencies {
    ...
    compile "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    compile 'com.google.dagger:dagger:2.0.2'
    kapt 'com.google.dagger:dagger-compiler:2.0.2'
    ...
}

You can check this project for reference

回答2:

I don't know when this change happened, but on 1.1.2 of the Kotlin gradle plugin you replace this (in your module's build.gradle):

kapt {
    generateStubs = true
}

with this:

apply plugin: 'kotlin-kapt'

and then make sure to replace dependencies that use annotationProcessor with kapt.

For example, the old way would be to use:

annotationProcessor (
    'some.library:one:1.0'
    ...
    'some.library.n:n.0'
)

and now you use:

kapt (
    'some.library:one:1.0'
    ...
    'some.library.n:n.0'
)

回答3:

UPDATE FOR KOTLIN 1.1.4

generateStubs does not work anymore. Feel free to make a build with the latest Kotlin and it would tell you in the Messages section of Android Studio that it is not necessary anymore. Here's an up-to-date list of dependencies for Dagger2 for Android and Kotlin

apply plugin: 'kotlin-kapt'

//...
// Other Gradle stuff
//...

dependencies {
    compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:1.1.4-3"

    compile 'com.google.dagger:dagger-android:2.12'
    kapt 'com.google.dagger:dagger-android-processor:2.12'
    compileOnly 'com.google.dagger:dagger:2.12'
    kapt 'com.google.dagger:dagger-compiler:2.12'
}

回答4:

This issue can be fixed with the bellow change which is different from original answer

Following will also work well to fix this issue

with plugins

apply plugin: 'kotlin-android'
apply plugin: 'kotlin-kapt'

and dependencies

implementation "com.google.dagger:dagger:$dagger_version"
implementation "com.google.dagger:dagger-android:$dagger_version"
implementation "com.google.dagger:dagger-android-support:$dagger_version" 
kapt "com.google.dagger:dagger-compiler:$dagger_version"
kapt "com.google.dagger:dagger-android-processor:$dagger_version"

For reference check out this Gist

回答5:

If u have problem withe DaggerComponent, You should add

apply plugin: 'kotlin-kapt'

kapt {
    generateStubs = true
}

to build.gradleit will generate kotlin code for dagger 2 otherwise project will only build on Rebuild

来源：https://stackoverflow.com/questions/34376061/dagger-and-kotlin-dagger-doesnt-generate-component-classes