在 Jetpack Compose 中解锁 CameraX 的强大功能

[versions]..camerax = "1.5.0-alpha03"accompanist = "0.36.0" # or whatever matches with your Compose version
[libraries]..# Contains the basic camera functionality such as SurfaceRequestandroidx-camera-core = { module = "androidx.camera:camera-core", version.ref = "camerax" }# Contains the CameraXViewfinder composableandroidx-camera-compose = { module = "androidx.camera:camera-compose", version.ref = "camerax" }# Allows us to bind the camera preview to our UI lifecycleandroidx-camera-lifecycle = { group = "androidx.camera", name = "camera-lifecycle", version.ref = "camerax" }# The specific camera implementation that renders the previewandroidx-camera-camera2 = { module = "androidx.camera:camera-camera2", version.ref = "camerax" }# The helper library to grant the camera permissionaccompanist-permissions = { module = "com.google.accompanist:accompanist-permissions", version.ref = "accompanist" }

dependencies {  ..  implementation(libs.androidx.camera.core)  implementation(libs.androidx.camera.compose)  implementation(libs.androidx.camera.lifecycle)  implementation(libs.androidx.camera.camera2)  implementation(libs.accompanist.permissions)}

<manifest xmlns:android="http://schemas.android.com/apk/res/android">    <uses-feature android:name="android.hardware.camera" android:required="true" />    <uses-permission android:name="android.permission.CAMERA" />
    ..
</manifest>

class MainActivity : ComponentActivity() {    override fun onCreate(savedInstanceState: Bundle?) {        super.onCreate(savedInstanceState)        enableEdgeToEdge()        setContent {            MyApplicationTheme {                CameraPreviewScreen()            }        }    }}
@OptIn(ExperimentalPermissionsApi::class)@Composablefun CameraPreviewScreen(modifier: Modifier = Modifier) {    val cameraPermissionState = rememberPermissionState(android.Manifest.permission.CAMERA)    if (cameraPermissionState.status.isGranted) {        CameraPreviewContent(modifier)    } else {        Column(            modifier = modifier.fillMaxSize().wrapContentSize().widthIn(max = 480.dp),            horizontalAlignment = Alignment.CenterHorizontally        ) {            val textToShow = if (cameraPermissionState.status.shouldShowRationale) {                // If the user has denied the permission but the rationale can be shown,                // then gently explain why the app requires this permission                "Whoops! Looks like we need your camera to work our magic!" +                    "Don't worry, we just wanna see your pretty face (and maybe some cats).  " +                    "Grant us permission and let's get this party started!"            } else {                // If it's the first time the user lands on this feature, or the user                // doesn't want to be asked again for this permission, explain that the                // permission is required                "Hi there! We need your camera to work our magic! ✨\n" +                    "Grant us permission and let's get this party started! \uD83C\uDF89"            }            Text(textToShow, textAlign = TextAlign.Center)            Spacer(Modifier.height(16.dp))            Button(onClick = { cameraPermissionState.launchPermissionRequest() }) {                Text("Unleash the Camera!")            }        }    }}
@Composableprivate fun CameraPreviewContent(modifier: Modifier = Modifier) {    // TODO: Implement}

class CameraPreviewViewModel : ViewModel() {    // Used to set up a link between the Camera and your UI.    private val _surfaceRequest = MutableStateFlow<SurfaceRequest?>(null)    val surfaceRequest: StateFlow<SurfaceRequest?> = _surfaceRequest
    private val cameraPreviewUseCase = Preview.Builder().build().apply {        setSurfaceProvider { newSurfaceRequest ->            _surfaceRequest.update { newSurfaceRequest }        }    }
    suspend fun bindToCamera(appContext: Context, lifecycleOwner: LifecycleOwner) {        val processCameraProvider = ProcessCameraProvider.awaitInstance(appContext)        processCameraProvider.bindToLifecycle(            lifecycleOwner, DEFAULT_FRONT_CAMERA, cameraPreviewUseCase        )
        // Cancellation signals we're done with the camera        try { awaitCancellation() } finally { processCameraProvider.unbindAll() }    }}

@Composablefun CameraPreviewContent(    viewModel: CameraPreviewViewModel,    modifier: Modifier = Modifier,    lifecycleOwner: LifecycleOwner = LocalLifecycleOwner.current) {    val surfaceRequest by viewModel.surfaceRequest.collectAsStateWithLifecycle()    val context = LocalContext.current    LaunchedEffect(lifecycleOwner) {         viewModel.bindToCamera(context.applicationContext, lifecycleOwner)     }
    surfaceRequest?.let { request ->        CameraXViewfinder(            surfaceRequest = request,            modifier = modifier        )    }}

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