Dagger2 nullable injection-CodePudding

I'm trying to inject Glide with Dagger.

So I have AppModule:

@Module
class AppModule {

    @Provides
    fun provideRequestOptions(): RequestOptions {
        return RequestOptions()
            .placeholder(R.drawable.white_background)
            .error(R.drawable.white_background)
    }

    @Provides
    fun provideGlideInstance(application: Application, requestOptions: RequestOptions): RequestManager{
        return Glide.with(application).setDefaultRequestOptions(requestOptions)
    }

    @Nullable
    @Provides
    fun provideAppDrawable(application: Application): Drawable? {
        return ContextCompat.getDrawable(application, R.drawable.logo)
    }
}

And AuthActivity:

class AuthActivity : DaggerAppCompatActivity() {
    lateinit var binding: ActivityAuthBinding
    @Inject
    lateinit var logo: Drawable
    @Inject
    lateinit var requestManager: RequestManager

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityAuthBinding.inflate(layoutInflater)
        setContentView(binding.root)

        setLogo()
        }

    private fun setLogo() {
        requestManager.load(logo).into(binding.loginLogo)
    }
}

provideAppDrawable() in AppModule has to return nullable Drawable?. When I'm trying to build app, Dagger complains about its nullability:

\AppComponent.java:7: error: [Dagger/Nullable] android.graphics.drawable.Drawable is not nullable, but is being provided by @org.jetbrains.annotations.Nullable @androidx.annotation.Nullable @Provides android.graphics.drawable.Drawable com.example.daggercodingwithmitch.di.AppModule.provideAppDrawable(android.app.Application)
public abstract interface AppComponent extends dagger.android.AndroidInjector<com.example.daggercodingwithmitch.BaseApplication> {

First I tried to make logo var in AuthActivity nullable, but lateinit can't be nullable. And if I don't use lateinit and make sth like this: var logo: Drawable? = null I get strange error abount private field injection even though it is not private:

\AuthActivity.java:10: error: Dagger does not support injection into private fields
    private android.graphics.drawable.Drawable logo;

How can I fix it? Thx.

CodePudding user response：

Easiest way is to make provideAppDrawable return a Drawable instead of a Drawable? and remove the @Nullable from it. Is there any scenario under which that returns null which isn't a bug? If not, it shouldn't be a nullable variable.

CodePudding user response：

You need to mark the filed "logo" @Nullable as well.

If a @Provides method is marked @Nullable, Dagger will only allow injection into sites that are marked @Nullable as well. A component that attempts to pair a @Nullable provision with a non-@Nullable injection site will fail to compile.

https://dagger.dev/api/2.28/dagger/Provides.html