A class to handle permission requests and callbacks for fragments in Android.

PermissionDelegate.kt

import android.content.Context
import android.content.pm.PackageManager
import androidx.core.content.ContextCompat
import androidx.fragment.app.Fragment

typealias GrantedCallback = () -> Unit
typealias DeniedCallback = () -> Unit

data class PermissionRequest(
    val requestCode: Int,
    val permission: String,
    val grantedCallback: GrantedCallback,
    val deniedCallback: DeniedCallback? = null
)

interface PermissionDelegate {
    fun performRequest(context: Context, fragment: Fragment, permissionRequest: PermissionRequest)

    fun onRequestPermissionsResult(
        requestCode: Int,
        permissions: Array<out String>,
        grantResults: IntArray
    )
}

class PermissionDelegateImpl(private val permissionRequests: List<PermissionRequest>) :
    PermissionDelegate {

    override fun performRequest(
        context: Context,
        fragment: Fragment,
        permissionRequest: PermissionRequest
    ) {
        require(permissionRequest in permissionRequests) { "$permissionRequest not found in submitted requests" }

        when (ContextCompat.checkSelfPermission(context, permissionRequest.permission)) {
            PackageManager.PERMISSION_GRANTED -> permissionRequest.grantedCallback()
            PackageManager.PERMISSION_DENIED -> fragment.requestPermissions(
                arrayOf(
                    permissionRequest.permission
                ), permissionRequest.requestCode
            )
        }
    }

    override fun onRequestPermissionsResult(
        requestCode: Int,
        permissions: Array<out String>,
        grantResults: IntArray
    ) {
        val permissionsResult = getPermissionResultMap(permissions, grantResults)

        permissionRequests.firstOrNull { it.requestCode == requestCode }?.let { permissionRequest ->
            permissionsResult[permissionRequest.permission]?.also {
                if (it) {
                    permissionRequest.grantedCallback()
                } else {
                    permissionRequest.deniedCallback?.invoke()
                }
            }
        }
    }

    private fun getPermissionResultMap(
        permissions: Array<out String>,
        grantResults: IntArray
    ): Map<String, Boolean> {
        val isGranted = { grantResult: Int -> grantResult == PackageManager.PERMISSION_GRANTED }

        val map = mutableMapOf<String, Boolean>()

        permissions.forEachIndexed { index: Int, value: String ->
            map[value] = isGranted(grantResults[index])
        }

        return map
    }
}

/* usage */

class UsageExample : Fragment() {
    private val permissionRequst =
        PermissionRequest(1, Manifest.permission.WRITE_EXTERNAL_STORAGE, {
            println("permission granted")
        })

    private val anotherPermissionRequeast =
        PermissionRequest(2, Manifest.permission.WRITE_CONTACTS, {
            println("also permission granted")
        })

    private val permissionDelegate =
        PermissionDelegateImpl(listOf(permissionRequst, anotherPermissionRequeast))

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        view.findViewById<Button>(R.id.button_color_blue).setOnClickListener {
            permissionDelegate.performRequest(requireContext(), this, permissionRequst)
        }

        view.findViewById<Button>(R.id.button_color_green).setOnClickListener {
            permissionDelegate.performRequest(requireContext(), this, anotherPermissionRequeast)
        }
    }

    override fun onRequestPermissionsResult(
        requestCode: Int,
        permissions: Array<out String>,
        grantResults: IntArray
    ) = permissionDelegate.onRequestPermissionsResult(requestCode, permissions, grantResults)
}