Permissions trong Android

1. Giới thiệu

Permissions bảo vệ quyền riêng tư của user bằng cách yêu cầu app xin phép trước khi truy cập sensitive data hoặc hardware.

2. Loại Permissions

Normal Permissions

Tự động được cấp, chỉ cần khai báo trong Manifest:


<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.VIBRATE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

Dangerous Permissions

Cần runtime request:

CAMERA
LOCATION
MICROPHONE
CONTACTS
CALENDAR
STORAGE
PHONE

3. Khai báo trong Manifest


<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.READ_CONTACTS" />
<uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
 
<!-- Storage permissions -->
<uses-permission android:name="android.permission.READ_MEDIA_IMAGES" />
<uses-permission android:name="android.permission.READ_MEDIA_VIDEO" />
<uses-permission android:name="android.permission.READ_MEDIA_AUDIO" />

4. Request Permission - Activity


class MainActivity : ComponentActivity() {
    
    private val requestPermissionLauncher = registerForActivityResult(
        ActivityResultContracts.RequestPermission()
    ) { isGranted ->
        if (isGranted) {
            openCamera()
        } else {
            showPermissionDeniedMessage()
        }
    }
    
    private fun checkCameraPermission() {
        when {
            checkSelfPermission(Manifest.permission.CAMERA) 
                == PackageManager.PERMISSION_GRANTED -> {
                openCamera()
            }
            shouldShowRequestPermissionRationale(Manifest.permission.CAMERA) -> {
                showRationaleDialog()
            }
            else -> {
                requestPermissionLauncher.launch(Manifest.permission.CAMERA)
            }
        }
    }
}

5. Multiple Permissions


private val requestMultiplePermissions = registerForActivityResult(
    ActivityResultContracts.RequestMultiplePermissions()
) { permissions ->
    val allGranted = permissions.entries.all { it.value }
    
    if (allGranted) {
        startLocationTracking()
    } else {
        // Check which permissions were denied
        permissions.forEach { (permission, granted) ->
            if (!granted) {
                handleDenied(permission)
            }
        }
    }
}
 
private fun requestLocationPermissions() {
    requestMultiplePermissions.launch(
        arrayOf(
            Manifest.permission.ACCESS_FINE_LOCATION,
            Manifest.permission.ACCESS_COARSE_LOCATION
        )
    )
}

6. Compose với Accompanist


// build.gradle.kts
implementation("com.google.accompanist:accompanist-permissions:0.34.0")

Single Permission


@OptIn(ExperimentalPermissionsApi::class)
@Composable
fun CameraScreen() {
    val cameraPermissionState = rememberPermissionState(Manifest.permission.CAMERA)
    
    when {
        cameraPermissionState.status.isGranted -> {
            CameraPreview()
        }
        cameraPermissionState.status.shouldShowRationale -> {
            Column {
                Text("Camera permission is required for this feature")
                Button(onClick = { cameraPermissionState.launchPermissionRequest() }) {
                    Text("Grant Permission")
                }
            }
        }
        else -> {
            Button(onClick = { cameraPermissionState.launchPermissionRequest() }) {
                Text("Request Camera Permission")
            }
        }
    }
}

Multiple Permissions


@OptIn(ExperimentalPermissionsApi::class)
@Composable
fun LocationScreen() {
    val locationPermissions = rememberMultiplePermissionsState(
        listOf(
            Manifest.permission.ACCESS_FINE_LOCATION,
            Manifest.permission.ACCESS_COARSE_LOCATION
        )
    )
    
    when {
        locationPermissions.allPermissionsGranted -> {
            LocationContent()
        }
        locationPermissions.shouldShowRationale -> {
            RationaleDialog(onConfirm = { locationPermissions.launchMultiplePermissionRequest() })
        }
        else -> {
            Button(onClick = { locationPermissions.launchMultiplePermissionRequest() }) {
                Text("Request Location Permissions")
            }
        }
    }
}

7. Xử lý “Don’t ask again”


if (!shouldShowRequestPermissionRationale(permission) 
    && checkSelfPermission(permission) != PackageManager.PERMISSION_GRANTED) {
    // User selected "Don't ask again"
    showSettingsDialog()
}
 
private fun showSettingsDialog() {
    AlertDialog.Builder(this)
        .setTitle("Permission Required")
        .setMessage("Please enable permission in Settings")
        .setPositiveButton("Settings") { _, _ ->
            val intent = Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS)
            intent.data = Uri.fromParts("package", packageName, null)
            startActivity(intent)
        }
        .setNegativeButton("Cancel", null)
        .show()
}

8. Permission Groups (Android 14+)


// Photo picker - không cần permission
val pickMedia = registerForActivityResult(ActivityResultContracts.PickVisualMedia()) { uri ->
    uri?.let { handleSelectedImage(it) }
}
 
pickMedia.launch(PickVisualMediaRequest(ActivityResultContracts.PickVisualMedia.ImageOnly))

9. Best Practices


// ✅ Good: Request khi cần
fun onCameraButtonClick() {
    requestCameraPermission()
}
 
// ❌ Bad: Request khi app start
override fun onCreate() {
    requestAllPermissions()  // Don't do this
}
 
// ✅ Good: Explain why
@Composable
fun PermissionRationale() {
    Column {
        Text("We need camera access to take photos for your profile")
        Button(onClick = { requestPermission() }) {
            Text("Continue")
        }
    }
}
 
// ✅ Good: Graceful degradation
if (hasLocationPermission) {
    showNearbyPlaces()
} else {
    showAllPlaces()  // Fallback without location
}

10. Special Permissions


// Overlay permission
if (!Settings.canDrawOverlays(this)) {
    val intent = Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION)
    startActivity(intent)
}
 
// Notification permission (Android 13+)
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
    requestPermissionLauncher.launch(Manifest.permission.POST_NOTIFICATIONS)
}

📝 Tóm tắt

Type	Request
Normal	Manifest only
Dangerous	Runtime request
Special	Intent to Settings

Best Practice	Description
Request in context	Khi user cần feature
Explain why	Show rationale
Handle denial	Graceful degradation
Don’t ask again	Link to Settings