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CameraX + Compose
Author: Adam Powell
Sample implementation of CameraX integration in a Composable
| suspend fun <R> withChildLifecycleOwner( | |
| parentLifecycle: Lifecycle, | |
| block: suspend CoroutineScope.(LifecycleOwner) -> R | |
| ): R { | |
| val childOwner = object : LifecycleOwner { | |
| val lifecycle = LifecycleRegistry(this) | |
| override fun getLifecycle(): Lifecycle = lifecycle | |
| } | |
| val registry = childOwner.lifecycle | |
| return coroutineScope { | |
| val myJob = coroutineContext.job | |
| val parentObserver = LifecycleEventObserver { _, event -> | |
| registry.currentState = event.targetState | |
| if (event == Lifecycle.Event.ON_DESTROY) { | |
| myJob.cancel("parent lifecycle was destroyed") | |
| } | |
| } | |
| parentLifecycle.addObserver(parentObserver) | |
| try { | |
| block(childOwner) | |
| } finally { | |
| parentLifecycle.removeObserver(parentObserver) | |
| registry.currentState = Lifecycle.State.DESTROYED | |
| } | |
| } | |
| } | |
| class CameraState { | |
| private val bindingMutex = MutatorMutex() | |
| var camera: Camera? by mutableStateOf(null) | |
| private set | |
| suspend fun <R> bind( | |
| context: Context, | |
| lifecycleOwner: LifecycleOwner, | |
| selector: CameraSelector, | |
| vararg useCases: UseCase, | |
| block: suspend (Camera) -> R | |
| ): R { | |
| val provider = ProcessCameraProvider.getInstance(context).await() | |
| return bindingMutex.mutate { | |
| withChildLifecycleOwner(lifecycleOwner.lifecycle) { childLifecycleOwner -> | |
| try { | |
| block( | |
| provider.bindToLifecycle(childLifecycleOwner, selector, *useCases) | |
| .also { this@CameraState.camera = it } | |
| ) | |
| } finally { | |
| camera = null | |
| } | |
| } | |
| } | |
| } | |
| } | |
| @Composable | |
| fun CameraBinding( | |
| state: CameraState, | |
| vararg useCases: UseCase, | |
| selectorBuilder: CameraSelector.Builder.() -> CameraSelector.Builder = { this } | |
| ) { | |
| // Make selectorBuilder observe snapshot changes and only rebuild the selector | |
| // when the builder changes. We do this since selectors don't implement equals | |
| // and this makes the API a little nicer since the caller doesn't need | |
| // to remember to remember {}. | |
| val currentSelectorBuilder by rememberUpdatedState(selectorBuilder) | |
| val selector by remember { | |
| derivedStateOf { | |
| CameraSelector.Builder().run(currentSelectorBuilder).build() | |
| } | |
| } | |
| val lifecycleOwner = LocalLifecycleOwner.current | |
| val context = LocalContext.current | |
| // useCases.toList() since arrays don't implement structural equality | |
| LaunchedEffect(state, selector, lifecycleOwner, useCases.toList()) { | |
| state.bind(context, lifecycleOwner, selector, *useCases) { | |
| awaitCancellation() | |
| } | |
| } | |
| } |
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