Kotlin - passing function as parameter via Intent

Question

I have this function in kotlin extension file to pass method but it doesn't work. Please explain me how it make correctly, I try this:

fun showErrorClientScreen(context: Context, action : () -> Unit) {
    val intent = Intent(context, RestClientErrorActivity::class.java)

    val bundle = Bundle()
    bundle.putSerializable(UPDATE_CLIENT_ERROR, ErrorClientListener {  action })
    intent.putExtra(UPDATE_CLIENT_ERROR_BUNDLE, bundle)

    context.startActivity(intent)
}

use java interface

public interface ErrorClientListener extends Serializable {

    void tryAgainFunction();

}

and my activity where i need listen click button and try again send request:

class RestClientErrorActivity: BaseActivity(), View.OnClickListener {

    private lateinit var errorClientListener: ErrorClientListener

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_rest_client_error)

        try {
            val bundle = intent.getBundleExtra(UPDATE_CLIENT_ERROR_BUNDLE)
            errorClientListener = bundle?.getSerializable(UPDATE_CLIENT_ERROR) as ErrorClientListener
        } catch (e: Exception) {
            e.message
        }
    }

    override fun onClick(v: View?) {
        when (v?.id) {
            R.id.ib_update -> errorClientListener.tryAgainFunction()
        }
    }

}

Answer 1

It is quite strange to package interfaces between activities and it is definitely not advisable. One reason why it is maybe not serializing between Activity A and Activity B is because the object was created in Activity A, it is treated as anonymous class creation and Activity A holds the reference to this object, hence preventing it from being serialised. This is good, because you can create references to objects within the interface callback whose reference in turn would be held by class instantiating it. Therefore, garbage collector won't be able to run collections on these objects and free up the space; causing a massive memory leak.

The alternative approach to your problem could be using clean architectures and a Singleton class pattern that is accessible by both activities and instantiated only once by say Activity A:

class SingletonErrorHandler private constructor(){
    var isError = false

    fun doOnError() {
        // do non view related stuff
        // like a network call or something          
    }

    companion object {
        val instance by lazy { SingletonErrorHandler() }
    }
}

in the activity you can define

class ActivityA : AppCompatActivity() {
    fun onError() {
        SingletonErrorHandler.instance.isError = true
    }
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.a_activity)
    }
}

in activity B

class ActivityB : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.b_activity)

        val errorHandler = SingletonErrorHandler.instance
        if(errorHandler.isError)
             errorHandler.doOnError()
    }
}