AndroidのカメラをUIに表示する【Androidアプリ開発】

<uses-feature
    android:name="android.hardware.camera"
    android:required="false" />
<uses-permission android:name="android.permission.CAMERA" />

implementation("androidx.camera:camera-camera2:1.3.1")
implementation("androidx.camera:camera-lifecycle:1.3.1")
implementation("androidx.camera:camera-view:1.3.1")

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            RtmpTestTheme {
                Surface(
                    modifier = Modifier.fillMaxSize(),
                    color = MaterialTheme.colorScheme.background
                ) {
                    // CameraPreview() に hasCameraPermission を渡します
                    CameraPreviewWithPermissionRequest()
                }
            }
        }
    }
}

@Composable
fun CameraPreviewWithPermissionRequest() {
    var hasCameraPermission by remember { mutableStateOf(false) }
    val context = LocalContext.current

    // パーミッションのリクエストの結果を受け取る Launcher
    val permissionLauncher = rememberLauncherForActivityResult(
        contract = ActivityResultContracts.RequestPermission(),
        onResult = { isGranted: Boolean ->
            hasCameraPermission = isGranted
        }
    )

    // アプリがフォアグラウンドに来たときにパーミッションの状態をチェック
    LaunchedEffect(key1 = true) {
        if (context.checkSelfPermission(android.Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
            permissionLauncher.launch(android.Manifest.permission.CAMERA)
        } else {
            hasCameraPermission = true
        }
    }

    if (hasCameraPermission) {
        CameraPreview()
    } else {
        Text("カメラのアクセス許可が必要です。")
    }
}

@Composable
fun CameraPreview() {
    val context = LocalContext.current
    val lifecycleOwner = LocalLifecycleOwner.current
    val cameraProviderFuture = remember { ProcessCameraProvider.getInstance(context) }
    val previewView = remember { PreviewView(context) } // CameraXライブラリの一部で、カメラのプレビューを表示するためのビュー
    val modifier = Modifier.fillMaxSize()

    AndroidView(
        modifier = modifier,
        factory = { previewView },
        update = { view ->
            val cameraProvider = cameraProviderFuture.get()
            val preview = Preview.Builder().build().also {
                it.setSurfaceProvider(view.surfaceProvider)
            }

            val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA
            try {
                cameraProvider.unbindAll()
                cameraProvider.bindToLifecycle(
                    lifecycleOwner, cameraSelector, preview
                )
            } catch(exc: Exception) {
                Log.e("CameraPreview", "Use case binding failed", exc)
            }
        }
    )
}

val context = LocalContext.current
val lifecycleOwner = LocalLifecycleOwner.current

val cameraProviderFuture = remember { ProcessCameraProvider.getInstance(context) }
val previewView = remember { PreviewView(context) }

AndroidView(
    modifier = modifier,
    factory = { previewView },
    update = { view ->
        // ...
    }
)

val cameraProvider = cameraProviderFuture.get()
val preview = Preview.Builder().build().also {
    it.setSurfaceProvider(view.surfaceProvider)
}

val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA
try {
    cameraProvider.unbindAll()
    cameraProvider.bindToLifecycle(
        lifecycleOwner, cameraSelector, preview
    )
} catch(exc: Exception) {
    Log.e("CameraPreview", "Use case binding failed", exc)
}