How to ask permission, the clean way - Droidcon 2021

Presentation at Droidcon 2021 by Ronaldo Pace
How to ask permission, the clean way
Tells the approach to implement Android Runtime permissions using a "clean" approach of service/repository/viewModel by the means decoupling it from the Android UI.

Transcript

1. How to ask permission,
   @ronaldopace
   (the clean way)
   

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2. Slide was added after the conference
   I decided I'll refactor my previous library
   "permission-bitte" into a V2 that will be the full
   implementation on what's on this presentation.
   This will be a nights and weekends deal,
   so might take a lil bit to complete.
   So if you're interested,
   be sure to watch or star the repo on
   https://github.com/budius/permission-bitte
   

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3. data
   (services)
   domain / business
   (repository)
   presentations
   (view/viewModel)
   The "clean" architecture
   

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4. class MyFragment {
   fun onSomethingClick() = when {
   ContextCompat.checkSelfPermission(this, Manifest.permission.REQUESTED_PERMISSION) == PackageManager.PERMISSION_GRANTED ->
   useTheApi()
   shouldShowRequestPermissionRationale(permissions) -> showPopUpToUser()
   else -> requestPermissions(this, arrayOf(Manifest.permission.REQUESTED_PERMISSION), REQUEST_CODE)
   }
   override fun onRequestPermissionsResult(
   requestCode: Int,
   permissions: Array,
   grantResults: IntArray
   ) {
   if ((grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED)) {
   useTheApi()
   } else {
   showPopUpToUser()
   }
   }
   }
   How to ask permission (according to the docs)
   

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5. How to "cleanly" ask permission (naively)
   class MyFragment {
   fun onSomethingClick() = when {
   ContextCompat.checkSelfPermission(this, Manifest.permission.REQUESTED_PERMISSION) == PackageManager.PERMISSION_GRANTED ->
   viewModel.useTheApi()
   shouldShowRequestPermissionRationale(permissions) -> showPopUpToUser()
   else -> requestPermissions(this, arrayOf(Manifest.permission.REQUESTED_PERMISSION), REQUEST_CODE)
   }
   override fun onRequestPermissionsResult(
   requestCode: Int,
   permissions: Array,
   grantResults: IntArray
   ) {
   if ((grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED)) {
   viewModel.useTheApi()
   } else {
   showPopUpToUser()
   }
   }
   }
   

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6. How to ask permission (with libraries)
   // delegates
   private val permissionDelegate = PermissionDelegate(this)
   fun onSomethingClick() {
   if (permissionDelegate.needsPermission(Manifest.permission.REQUESTED_PERMISSION))
   permission.request(Manifest.permission.REQUESTED_PERMISSION)
   }
   override fun onRequestPermissionsResult(requestCode: Int, permissions: Array,
   grantResults: IntArray) = permissionDelegate.result(requestCode, permissions, grantResults)
   // annotation
   @NeedsPermission(Manifest.permission.REQUESTED_PERMISSION)
   fun onSomethingElseClick() {
   // permission was approved
   }
   @OnPermissionResult(Manifest.permission.REQUESTED_PERMISSION)
   fun onRequestPermissionResult(result: Code) {
   // handle result here
   }
   

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7. Are they really clean,
   if all that logic is on the presentation layer?
   data
   (services)
   domain / business
   (repository)
   presentations
   (view/viewModel)
   (don´t forget to mention DRY)
   

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8. interface PermissionService {
   val permissions: Flow>
   suspend fun requestPermissions(permissions: Set)
   }
   data class Permission(val name: String, state: PermissionState)
   enum class PermissionState {
   GRANTED,
   REQUEST_PERMISSION,
   DENIED,
   SHOW_RATIONALE
   }
   PermissionService.kt
   data
   (services)
   domain / business
   (repository)
   presentations
   (view/viewModel)
   

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9. Dividing the problem: List
   Just copy from: https://github.com/budius/permission-bitte
   class PermissionServiceImpl(app: Application) : PermissionService {
   private val _permissions = MutableStateFlow(extractPermissionsFromManifest(app))
   override val permissions = _permissions.map{ mapToSet(it) }.distinctUntilChanged()
   }
   private fun extractPermissionsFromManifest(context: Context): Map {
   val pm = context.packageManager
   val info = pm.getPackageInfo(context.getPackageName(), PackageManager.GET_PERMISSIONS)
   val names = info.requestedPermissions
   val groups = names.map { pm.getPermissionInfo(name, 0).group }
   val flags = info.requestedPermissionsFlags
   // parse name, group, flags into Map
   // but DENIED can´t be obtained here =(
   map[name] = GRANTED / REQUEST_PERMISSION / SHOW_RATIONALE
   

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10. Dividing the problem: Updating from outside the app
    class PermissionServiceImpl(app: Application) : PermissionService {
    private val activityCallback = object : ActivityLifecycleCallbacks {
    override fun onActivityResumed(activity: Activity) {
    val newData = extractPermissionsFromManifest(activity)
    _permissions.value = updatePermissions(newData, _permissions.value)
    }
    }
    }
    private fun updatePermissions(
    newData: Map,
    current: Map
    ): Map {
    // any permissions that current is DENIED,
    // must stay DENIED
    // the others, pick from the newData
    }
    

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11. class PermissionServiceImpl {
    private var pendingResult: CompletableDeferred? = null
    override suspend fun requestPermissions(permissions: Set) {
    val request = filter(permissions) ?: return
    pendingResult = CompletableDeferred().also {
    requestPermissionInternal(permissions, it) // magic ?
    }
    val result = pendingResult.await()
    val newData: Map = parseResult(result)
    _permissions.value = updatePermissions(newData, _permissions.value)
    }
    }
    private data class RequestResult(val permissions: Array, val grantResults: IntArray)
    Dividing the problem: Prepare the request
    

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12. class PermissionFragment : Fragment() {
    private var pendingResult: CompletableDeferred? = null
    override fun onResume() {
    super.onResume()
    requestPermissions(requireArguments().getStringArray("permissions")!!, 42)
    }
    override fun onRequestPermissionsResult(requestCode: Int, permissions: Array, grantResults: IntArray) {
    pendingResult?.let {
    it.complete("")
    pendingResult = null
    }
    }
    fun setPendingResult(pendingResult: CompletableDeferred) {
    this.pendingResult = pendingResult
    }
    }
    Dividing the problem: Request permission
    

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13. Dividing the problem: Triggering the request
    class PermissionServiceImpl {
    private var pendingResult: CompletableDeferred? = null
    private lateinit var currentActivity: WeakReferenced
    override fun onActivityCreated(activity: Activity) {
    pendingRequest?.let { addPermissionFragment(activity, pendingResult) }
    }
    override fun onActivityStarted(activity: Activity) {
    if (activity is FragmentActivity) currentActivity = WeakReferenced(activity)
    }
    private fun requestPermissionInternal(permissions: Set,
    pendingResult: CompletableDeferred) {
    currentActivity.get()?.supportFragmentManager.beginTransaction()
    .add(PermissionFragment().apply {
    arguments = Bundle().apply { putStringArray("permissions", val) }
    setPendingResult(pendingResult)}, "permission-fragment").commit()
    }
    }
    

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14. Is it clean now?
    data
    (services)
    domain / business
    (repository)
    presentations
    (view/viewModel)
    PermissionFragment
    PermissonServiceImpl
    PermissionService
    PermissionRepo LocationRepo
    Onboarding V-VM SomeMapThing V-VM
    Google Play Services
    - Location
    

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15. Questions?
    @ronaldopace
    

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