Android - How to pass a function to an Activity?

Question

I am attempting to create a Builder for an activity. The reason is because this activity can be started many different ways. I created a Builder class like this:

class ActivityBuilder {

    private var showToolBar = false
    private var postExecutable: (() -> Unit)? = null

    fun showToolbar(boolean: Boolean) : ActivityBuilder {
        this.showToolBar = boolean
        return this
    }

    fun setPostExecutable(function: () -> Unit) : ActivityBuilder {
        this.postExecute = function
        return this
    }

    fun start(context: Context){
        val intent = Intent(context, Activity::class.java)
        context.startActivity(intent)
    }
}

The idea is to call something like this and have access to these fields inside of the activity.

 ActivityBuilder().showToolbar(false).setPostExecutable { { doSomething() } }.start(this)

I guess I could also use a companion object and that would serve the same purpose.

companion object Builder {

    private var showToolBar = false
    private var postExecute: (() -> Unit)? = null

    fun showToolbar(boolean: Boolean) : Builder {
        this.showToolBar = boolean
        return this
    }

    fun setPostExecutable(function: () -> Unit) : Builder {
        this.postExecute = function
        return this
    }

    fun start(context: Context){
        val intent = Intent(context, AuthActivity::class.java)
        context.startActivity(intent)
    }
}

The issue is coming mostly from the "postExecutable" field. I need to call the function at a certain point but it is not parcelable, so I cannot pass it through the intent when starting activity.

If anyone has a solution, I appreciate it!

Answer 1

This is one solution I found, may not be the most elegant. I created a broadcast receiver that I start at the same time as my activity using the parent context.

class ActivityBuilder(private val context: Context) {

    private var postSuccessExecutable: (() -> Unit)? = null
    ...
    private fun setupReceiver(){

        val filter = IntentFilter()
        filter.addAction("SUCCESS")

        val receiver = object : BroadcastReceiver() {
            override fun onReceive(c: Context?, intent: Intent?) {

                context.unregisterReceiver(this)

                if (intent?.action == "SUCCESS"){
                    Toast.makeText(context, "Successful", Toast.LENGTH_SHORT).show()
                    postSuccessExecutable?.invoke()
                }
            }
        }

        context.registerReceiver(authReceiver, filter)
    }
    ...
}

When I want to trigger the function, I just send a broadcast:

private fun sendSuccessBroadcast(data: String){
    val intent = Intent()
    intent.action = "SUCCESS"
    intent.putExtra("data", String)
    requireContext().sendBroadcast(intent)
}