Track state of camera permission

app/src/main/java/org/mydomain/myscan/CameraPermission.kt

@@ -22,27 +22,34 @@ import androidx.activity.compose.ManagedActivityResultLauncher
 import androidx.activity.compose.rememberLauncherForActivityResult
 import androidx.activity.result.contract.ActivityResultContracts
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.Stable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
 import androidx.compose.ui.platform.LocalContext
 import androidx.core.content.ContextCompat
 
-fun hasCameraPermission(context: Context): Boolean {
+private fun hasCameraPermission(context: Context): Boolean {
     val camera = Manifest.permission.CAMERA
     return ContextCompat.checkSelfPermission(context, camera) == PackageManager.PERMISSION_GRANTED
 }
 
-@Composable
+@Stable
-fun rememberCameraPermissionLauncher(
+class CameraPermissionState internal constructor(
-    onGranted: () -> Unit = {},
+    private val context: Context,
-    onDenied: () -> Unit = {}
+    private val launcher: ManagedActivityResultLauncher<String, Boolean>
-): ManagedActivityResultLauncher<String, Boolean> {
+) {
-    val context = LocalContext.current
+    var isGranted by mutableStateOf(hasCameraPermission(context))
-    return rememberLauncherForActivityResult (
+        private set
-        ActivityResultContracts.RequestPermission()
+
-    ) { isGranted ->
+    fun request() {
-        if (isGranted) {
+        launcher.launch(Manifest.permission.CAMERA)
-            onGranted()
+    }
-        } else {
+
-            onDenied()
+    internal fun update(granted: Boolean) {
+        isGranted = granted
+        if (!granted) {
             Toast.makeText(
                 context,
                 context.getString(R.string.camera_permission_denied),
@@ -51,3 +58,21 @@ fun rememberCameraPermissionLauncher(
         }
     }
 }
+
+@Composable
+fun rememberCameraPermissionState(): CameraPermissionState {
+    val context = LocalContext.current
+    lateinit var state: CameraPermissionState
+
+    val launcher = rememberLauncherForActivityResult(
+        ActivityResultContracts.RequestPermission()
+    ) { granted ->
+        state.update(granted)
+    }
+
+    state = remember {
+        CameraPermissionState(context, launcher)
+    }
+
+    return state
+}

app/src/main/java/org/mydomain/myscan/MainActivity.kt

@@ -60,6 +60,7 @@ class MainActivity : ComponentActivity() {
             val currentScreen by viewModel.currentScreen.collectAsStateWithLifecycle()
             val liveAnalysisState by viewModel.liveAnalysisState.collectAsStateWithLifecycle()
             val document by viewModel.documentUiModel.collectAsStateWithLifecycle()
+            val cameraPermission = rememberCameraPermissionState()
             MyScanTheme {
                 val navigation = Navigation(
                     toHomeScreen = { viewModel.navigateTo(Screen.Home) },
@@ -72,7 +73,7 @@ class MainActivity : ComponentActivity() {
                 when (val screen = currentScreen) {
                     is Screen.Home -> {
                         HomeScreen(
-                            hasCameraPermission = hasCameraPermission(this),
+                            cameraPermission = cameraPermission,
                             currentDocument = document,
                             navigation = navigation,
                             onStartNewScan = navigation.toCameraScreen,
@@ -85,6 +86,7 @@ class MainActivity : ComponentActivity() {
                             liveAnalysisState,
                             onImageAnalyzed = { image -> viewModel.liveAnalysis(image) },
                             onFinalizePressed = { viewModel.navigateTo(Screen.Document()) },
+                            cameraPermission = cameraPermission
                         )
                     }
                     is Screen.Document -> {

app/src/main/java/org/mydomain/myscan/view/CameraPreview.kt

@@ -52,10 +52,9 @@ import androidx.core.graphics.scale
 import androidx.lifecycle.LifecycleOwner
 import androidx.lifecycle.compose.LocalLifecycleOwner
 import com.google.common.util.concurrent.ListenableFuture
+import org.mydomain.myscan.CameraPermissionState
 import org.mydomain.myscan.LiveAnalysisState
 import org.mydomain.myscan.Point
-import org.mydomain.myscan.hasCameraPermission
-import org.mydomain.myscan.rememberCameraPermissionLauncher
 import org.mydomain.myscan.scaledTo
 import java.util.concurrent.ExecutorService
 import java.util.concurrent.Executors
@@ -66,13 +65,12 @@ fun CameraPreview(
     onImageAnalyzed: (ImageProxy) -> Unit,
     captureController: CameraCaptureController,
     onPreviewViewReady: (PreviewView) -> Unit,
+    cameraPermission: CameraPermissionState,
 ) {
     val context = LocalContext.current
-    val requestPermissionLauncher = rememberCameraPermissionLauncher(onGranted = {}, onDenied = {})
     LaunchedEffect(Unit) {
-        val camera = android.Manifest.permission.CAMERA
+        if (!cameraPermission.isGranted) {
-        if (!hasCameraPermission(context)) {
+            cameraPermission.request()
-            requestPermissionLauncher.launch(camera)
         }
     }
 

app/src/main/java/org/mydomain/myscan/view/CameraScreen.kt

@@ -75,6 +75,7 @@ import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import kotlinx.coroutines.delay
+import org.mydomain.myscan.CameraPermissionState
 import org.mydomain.myscan.LiveAnalysisState
 import org.mydomain.myscan.MainViewModel
 import org.mydomain.myscan.MainViewModel.CaptureState
@@ -102,6 +103,7 @@ fun CameraScreen(
     liveAnalysisState: LiveAnalysisState,
     onImageAnalyzed: (ImageProxy) -> Unit,
     onFinalizePressed: () -> Unit,
+    cameraPermission: CameraPermissionState,
 ) {
     var previewView by remember { mutableStateOf<PreviewView?>(null) }
     val document by viewModel.documentUiModel.collectAsStateWithLifecycle()
@@ -145,7 +147,8 @@ fun CameraScreen(
             CameraPreview(
                 onImageAnalyzed = onImageAnalyzed,
                 captureController = captureController,
-                onPreviewViewReady = { view -> previewView = view }
+                onPreviewViewReady = { view -> previewView = view },
+                cameraPermission = cameraPermission,
             )
         },
         pageListState =

app/src/main/java/org/mydomain/myscan/view/HomeScreen.kt

@@ -14,7 +14,6 @@
  */
 package org.mydomain.myscan.view
 
-import android.Manifest
 import androidx.compose.foundation.Image
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
@@ -46,15 +45,16 @@ import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
+import org.mydomain.myscan.CameraPermissionState
 import org.mydomain.myscan.Navigation
 import org.mydomain.myscan.R
-import org.mydomain.myscan.rememberCameraPermissionLauncher
+import org.mydomain.myscan.rememberCameraPermissionState
 import org.mydomain.myscan.ui.theme.MyScanTheme
 
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
 fun HomeScreen(
-    hasCameraPermission: Boolean,
+    cameraPermission: CameraPermissionState,
     currentDocument: DocumentUiModel,
     navigation: Navigation,
     onStartNewScan: () -> Unit
@@ -95,8 +95,8 @@ fun HomeScreen(
                 .fillMaxSize()
                 .verticalScroll(rememberScrollState())
         ) {
-            if (!hasCameraPermission) {
+            if (!cameraPermission.isGranted) {
-                CameraPermissionRationale()
+                CameraPermissionRationale(cameraPermission)
             }
 
             if (!currentDocument.isEmpty()) {
@@ -115,8 +115,7 @@ fun HomeScreen(
 }
 
 @Composable
-private fun CameraPermissionRationale() {
+private fun CameraPermissionRationale(cameraPermission: CameraPermissionState) {
-    val requestPermissionLauncher = rememberCameraPermissionLauncher(onGranted = {}, onDenied = {})
     Card(
         modifier = Modifier
             .fillMaxWidth()
@@ -128,9 +127,7 @@ private fun CameraPermissionRationale() {
                 style = MaterialTheme.typography.bodyMedium
             )
             Spacer(Modifier.height(8.dp))
-            Button(onClick = {
+            Button(onClick = { cameraPermission.request() }) {
-                requestPermissionLauncher.launch(Manifest.permission.CAMERA)
-            }) {
                 Text(stringResource(R.string.grant_permission))
             }
         }
@@ -183,7 +180,7 @@ private fun SectionTitle(text: String) {
 fun HomeScreenPreviewOnFirstLaunch() {
     MyScanTheme {
         HomeScreen(
-            hasCameraPermission = false,
+            cameraPermission = rememberCameraPermissionState(),
             currentDocument = DocumentUiModel(listOf()) { _ -> null },
             navigation = dummyNavigation(),
             onStartNewScan = {}
@@ -196,7 +193,7 @@ fun HomeScreenPreviewOnFirstLaunch() {
 fun HomeScreenPreviewWithCurrentDocument() {
     MyScanTheme {
         HomeScreen(
-            hasCameraPermission = true,
+            cameraPermission = rememberCameraPermissionState(),
             currentDocument = fakeDocument(
                 listOf("gallica.bnf.fr-bpt6k5530456s-1.jpg"),
                 LocalContext.current),