相机与媒体 (Camera & Media)

Compose 目前没有原生的 Camera 或 Video 组件，我们需要通过 AndroidView 来桥接 Android 原生的 CameraX 和 ExoPlayer。

1. 相机预览 (CameraX)

依赖

val camerax_version = "1.3.1"
implementation("androidx.camera:camera-core:${camerax_version}")
implementation("androidx.camera:camera-camera2:${camerax_version}")
implementation("androidx.camera:camera-lifecycle:${camerax_version}")
implementation("androidx.camera:camera-view:${camerax_version}")

实现 CameraPreview

@Composable
fun CameraPreview(
    modifier: Modifier = Modifier,
    scaleType: PreviewView.ScaleType = PreviewView.ScaleType.FILL_CENTER,
    cameraSelector: CameraSelector = CameraSelector.DEFAULT_BACK_CAMERA
) {
    val lifecycleOwner = LocalLifecycleOwner.current
    
    AndroidView(
        modifier = modifier,
        factory = { context ->
            val previewView = PreviewView(context).apply {
                this.scaleType = scaleType
            }
            
            // 获取 CameraProvider
            val cameraProviderFuture = ProcessCameraProvider.getInstance(context)
            
            cameraProviderFuture.addListener({
                val cameraProvider = cameraProviderFuture.get()
                
                // 创建 Preview 用例
                val preview = Preview.Builder().build().also {
                    it.setSurfaceProvider(previewView.surfaceProvider)
                }

                try {
                    // 解绑所有并重新绑定
                    cameraProvider.unbindAll()
                    cameraProvider.bindToLifecycle(
                        lifecycleOwner,
                        cameraSelector,
                        preview
                    )
                } catch (e: Exception) {
                    Log.e("CameraPreview", "Use case binding failed", e)
                }
            }, ContextCompat.getMainExecutor(context))
            
            previewView
        }
    )
}

2. 视频播放 (ExoPlayer)

依赖

implementation("androidx.media3:media3-exoplayer:1.2.0")
implementation("androidx.media3:media3-ui:1.2.0")

实现 VideoPlayer

@Composable
fun VideoPlayer(uri: Uri) {
    val context = LocalContext.current
    
    // 初始化 ExoPlayer
    val exoPlayer = remember {
        ExoPlayer.Builder(context).build().apply {
            setMediaItem(MediaItem.fromUri(uri))
            prepare()
            playWhenReady = true
        }
    }

    // 记得在组件销毁时释放 Player
    DisposableEffect(Unit) {
        onDispose {
            exoPlayer.release()
        }
    }

    // 使用 PlayerView
    AndroidView(
        factory = { ctx ->
            PlayerView(ctx).apply {
                player = exoPlayer
            }
        },
        modifier = Modifier
            .fillMaxWidth()
            .aspectRatio(16f / 9f) // 保持 16:9
    )
}

生命周期处理

对于视频播放器，通常还需要处理 onPause (暂停播放) 和 onResume (恢复播放)。可以通过监听 LocalLifecycleOwner 来实现。