Request permissions from any Activity (not just FragmentActivity)

[Luiz Machado]

It seems we need the FragmentManager to be able to request permissions with Splitties, it would be nice if we could request perimssions from the AndroidViewModel context using just the application.

Here is some example code on how to do that:

package com.example

import android.content.Context
import android.content.Intent
import android.content.pm.PackageManager
import android.os.Bundle
import android.os.Parcelable
import androidx.appcompat.app.AppCompatActivity
import androidx.core.app.ActivityCompat
import br.com.havan.apps.havanapp.R
import kotlinx.android.parcel.Parcelize
import java.util.concurrent.ConcurrentHashMap

@Parcelize
class PermissionResult(val permission: String, val state: State) : Parcelable

enum class State { GRANTED, DENIED_TEMPORARILY, DENIED_PERMANENTLY }

typealias Cancellable = () -> Unit

private const val PERMISSIONS_ARGUMENT_KEY = "PERMISSIONS_ARGUMENT_KEY"
private const val REQUEST_CODE_ARGUMENT_KEY = "REQUEST_CODE_ARGUMENT_KEY"

object PermissionRequester {
    private val callbackMap = ConcurrentHashMap<Int, (List<PermissionResult>) -> Unit>(1)
    private var requestCode = 256
        get() {
            requestCode = field--
            return if (field < 0) 255 else field
        }

    fun requestPermissions(context: Context, vararg permissions: String, callback: (List<PermissionResult>) -> Unit): Cancellable {
        val intent = Intent(context, PermissionRequestActivity::class.java)
            .putExtra(PERMISSIONS_ARGUMENT_KEY, permissions)
            .putExtra(REQUEST_CODE_ARGUMENT_KEY, requestCode)
            .addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
        context.startActivity(intent)
        callbackMap[requestCode] = callback
        return { callbackMap.remove(requestCode) }
    }

    internal fun onPermissionResult(responses: List<PermissionResult>, requestCode: Int) {
        callbackMap[requestCode]?.invoke(responses)
        callbackMap.remove(requestCode)
    }
}

class PermissionRequestActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        if (savedInstanceState == null) {
            requestPermissions()
        }
    }

    private fun requestPermissions() {
        val permissions = intent?.getStringArrayExtra(PERMISSIONS_ARGUMENT_KEY) ?: arrayOf()
        val requestCode = intent?.getIntExtra(REQUEST_CODE_ARGUMENT_KEY, -1) ?: -1
        when {
            permissions.isNotEmpty() && requestCode != -1 -> ActivityCompat.requestPermissions(this, permissions, requestCode)
            else -> finishWithResult()
        }
    }

    override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<String>, grantResults: IntArray) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)

        val permissionResults = grantResults.zip(permissions).map { (grantResult, permission) ->
            val state =  when {
                grantResult == PackageManager.PERMISSION_GRANTED -> State.GRANTED
                ActivityCompat.shouldShowRequestPermissionRationale(this, permission) -> State.DENIED_TEMPORARILY
                else -> State.DENIED_PERMANENTLY
            }
            PermissionResult(permission, state)
        }

        finishWithResult(permissionResults)
    }

    private fun finishWithResult(permissionResult: List<PermissionResult> = listOf()) {
        val requestCode = intent?.getIntExtra(REQUEST_CODE_ARGUMENT_KEY, -1) ?: -1
        PermissionRequester.onPermissionResult(permissionResult, requestCode)
        finish()
    }
}

You just need to register the PermissionRequestActivity in the AppManifest and you are all set to use PermissionRequester.requestPermissions passing down two parameters: the app context and the list of permissions names you want.

[Louis CAD]

AndroidX ViewModel is not the right place to expose such an API IMO. It's better exposed in the UI, which is hosted in an Activity.
That said, I see a way to not require a FragmentActivity and allow it for any Activity. It's not on my priority list at the moment though.