still got error Unresolved reference even with the -keep class

Question

In the project it has a class in OptionalDependencies.kt

package com.xyz.demo

import android.content.Context
import com.facebook.stetho.Stetho
import com.facebook.stetho.okhttp3.StethoInterceptor
import okhttp3.Interceptor

object OptionalDependencies {

    fun initStetho(context: Context) {
        Stetho.initializeWithDefaults(context)
    }

    fun getNetworkInterceptor() : Interceptor?  = StethoInterceptor()

}

and in the StartActivity.kt

package com.xyz.demo.ui

import com.xyz.demo.OptionalDependencies
……

class StartActivity : AppCompatActivity() {

    private fun initStetho(@ApplicationContext appContext: Context) {

        val interceptor : Interceptor? = 
                OptionalDependencies.getNetworkInterceptor()//<=== any where will get error referring the 
        ……
    }

    ……
}

in the build.gradle

buildTypes {
    debug {
        minifyEnabled true
        shrinkResources true
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'

    }
}

in the proguard-rules.pro

-keep class com.xyz.demo.** {*;}

also tried -keep class com.xyz.demo.OptionalDependencies {*;}

get error: e:/Users/sample/src/main/java/com/xyz/demo/ui/StartActivity.kt: (527, 42): Unresolved reference: OptionalDependencies

if turn off the proguard it works fine.

Answer 1

I guess have to do a "sync" after made change to the proguard-rules.pro, then re-build.