如何使用camera-viewfinder-compose库在Jetpack Compose中获取相机预览？

1. 添加依赖 #

在Module级别的build.gradle文件中引入CameraX相关依赖：

dependencies {
    // Viewfinder Compose组件
    implementation "androidx.camera:camera-viewfinder-compose:1.0.0-alpha02"
    // CameraX核心依赖
    implementation "androidx.camera:camera-core:1.3.0"
    implementation "androidx.camera:camera-camera2:1.3.0"
    implementation "androidx.camera:camera-lifecycle:1.3.0"
}

2. 配置相机权限 #

在AndroidManifest.xml中添加必要权限：

<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" />
<uses-feature android:name="android.hardware.camera.autofocus" />
<!-- 如需录像功能，添加录音权限 -->
<uses-permission android:name="android.permission.RECORD_AUDIO" />

3. 完整实现流程 #

3.1 权限检查与请求 #

在Compose中先处理相机权限授权逻辑：

val context = LocalContext.current
val cameraPermissionState = rememberPermissionState(android.Manifest.permission.CAMERA)

LaunchedEffect(Unit) {
    if (!cameraPermissionState.hasPermission) {
        cameraPermissionState.launchPermissionRequest()
    }
}

3.2 初始化CameraX并获取预览所需参数 #

通过ProcessCameraProvider绑定相机生命周期，生成SurfaceRequest和ViewfinderTransformationInfo：

val lifecycleOwner = LocalLifecycleOwner.current
val cameraProviderFuture = remember { ProcessCameraProvider.getInstance(context) }

var surfaceRequest by remember { mutableStateOf<SurfaceRequest?>(null) }
var transformationInfo by remember { mutableStateOf<ViewfinderTransformationInfo?>(null) }

LaunchedEffect(cameraPermissionState.hasPermission) {
    if (cameraPermissionState.hasPermission) {
        val cameraProvider = cameraProviderFuture.get()
        val preview = Preview.Builder().build()
        val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA

        try {
            // 解绑原有相机绑定
            cameraProvider.unbindAll()
            val camera = cameraProvider.bindToLifecycle(lifecycleOwner, cameraSelector, preview)

            // 监听Surface请求
            preview.setSurfaceProvider { request ->
                surfaceRequest = request as SurfaceRequest
                // 提供Surface完成预览请求
                request.provideSurface(request.surface, context.mainExecutor) {
                    // 处理Surface释放逻辑
                }
            }

            // 获取画面变换信息，适配屏幕旋转与相机传感器方向
            transformationInfo = ViewfinderTransformationInfo(
                cameraInfo = camera.cameraInfo,
                displayRotation = context.display?.rotation ?: 0
            )
        } catch (e: Exception) {
            // 处理相机绑定失败异常
            e.printStackTrace()
        }
    }
}

3.3 渲染Viewfinder组件 #

将获取到的参数传入Viewfinder，实现相机预览：

if (surfaceRequest != null && transformationInfo != null) {
    Viewfinder(
        surfaceRequest = surfaceRequest!!,
        // 可选PERFORMANCE（优先硬件加速）或COMPATIBILITY（适配旧设备）
        implementationMode = ViewfinderImplementationMode.PERFORMANCE,
        transformationInfo = transformationInfo!!
    )
} else {
    // 相机未准备或权限未授权时的占位UI
    Box(modifier = Modifier.fillMaxSize(), contentAlignment = Alignment.Center) {
        Text(text = "相机准备中或未授权")
    }
}

关键参数说明 #

• surfaceRequest: 由CameraX的Preview组件提供，是相机预览画面的Surface请求载体，负责将相机输出渲染到Viewfinder。
• implementationMode: 控制预览的渲染模式，PERFORMANCE优先使用硬件加速，性能更优；COMPATIBILITY适配更多旧设备，性能稍低。
• transformationInfo: 包含相机传感器信息与屏幕旋转数据，用于自动调整预览画面的缩放、旋转角度，保证画面无畸变、方向正确。

内容的提问来源于stack exchange，提问作者Muscle Code