CameraX使用

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#android #kotlin #CameraX

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本文介绍了如何在Android应用中集成CameraX库，包括添加依赖、权限声明、PreviewView使用和自定义配置。重点讲解了CameraX的UseCase和关键API，如选择相机、拍照和录像功能的实现。

添加依赖

def camerax_version = "1.1.0-beta03"
// CameraX core library
implementation "androidx.camera:camera-core:$camerax_version"
// CameraX Camera2 extensions[可选]拓展库可实现人像、HDR、夜间和美颜、滤镜但依赖于OEM
implementation "androidx.camera:camera-camera2:$camerax_version"
// CameraX Lifecycle library[可选]避免手动在生命周期释放和销毁数据
implementation "androidx.camera:camera-lifecycle:$camerax_version"
// CameraX View class[可选]最佳实践，最好用里面的PreviewView，它会自行判断用SurfaceView还是TextureView来实现
implementation 'androidx.camera:camera-view:1.1.0-beta03'

在build.gradle中添加CameraX依赖，最新版本可以从官网链接查看

声明权限

<uses-feature android:name="android.hardware.camera.any" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.RECORD_AUDIO" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

在AndroidManifest.xml中声明需要使用的权限

添加PreviewView布局

<androidx.camera.view.PreviewView
    android:id="@+id/preview"
    android:layout_height="match_parent"
    android:layout_width="match_parent" />

PreviewView可以根据不同场景，自行区分使用SurfaceView或者TextureView

自定义配置Camera

class CameraApplication : Application(), CameraXConfig.Provider {
   override fun getCameraXConfig(): CameraXConfig {
       return CameraXConfig.Builder.fromConfig(Camera2Config.defaultConfig())
           .setMinimumLoggingLevel(Log.ERROR).build()
   }
}

CameraXConfig用于自定义相机的初始配置

检查Camera可用性

private fun openCamera() {
    var cameraProviderFuture = ProcessCameraProvider.getInstance(requireContext())
    cameraProviderFuture.addListener({
        cameraProvider = cameraProviderFuture.get()
        bindPreview(cameraProvider)
    }, ContextCompat.getMainExecutor(requireContext()))
}

选择相机、绑定生命周期并添加usecase

private fun bindPreview(cameraProvider: ProcessCameraProvider) {
  	cameraSelector = CameraSelector.Builder()
        .requireLensFacing(CameraSelector.LENS_FACING_BACK).build()

    preview = Preview.Builder()
        .setTargetAspectRatio(AspectRatio.RATIO_16_9)  //设置宽高比
        .setTargetRotation(Surface.ROTATION_0)
        .build()
    preview.setSurfaceProvider(previewView.surfaceProvider)

    imageCapture = ImageCapture.Builder()
        .setTargetRotation(requireView().display.rotation)
        .build()

    val recorder = Recorder.Builder().build()
    videoCapture = VideoCapture.withOutput(recorder)

    try {
        cameraProvider.unbindAll()
        cameraProvider.bindToLifecycle(viewLifecycleOwner, cameraSelector, videoCapture, imageCapture, preview)
    } catch (e: Exception) {
        Log.e(TAG, "bind preview error: $e")
    }
}

查看bindToLifecycle方法可以看到，CameraX定义了一个UseCase的概念，以满足不同场景下Camera的使用，如代码中的preview、imageCapture、videoCapture分别用于展示预览、拍摄照片、录制视频，同时也可以写成以下形式：

val useCaseGroup = UseCaseGroup.Builder()
    .addUseCase(preview)
    .addUseCase(imageCapture)
    .addUseCase(videoCapture)
    .build()

try {
    cameraProvider.unbindAll()
    cameraProvider.bindToLifecycle(viewLifecycleOwner, cameraSelector, useCaseGroup)
} catch (e: Exception) {
    Log.e(TAG, "bind preview error: $e")
}

拍摄照片

private fun takePicture() {
    var path = requireContext().cacheDir.canonicalPath + getFileName("jpeg")
    val outputFileOptions = ImageCapture.OutputFileOptions.Builder(File(path)).build()
  
    imageCapture.takePicture(outputFileOptions, ContextCompat.getMainExecutor(requireContext()),
        object : ImageCapture.OnImageSavedCallback {
            override fun onImageSaved(outputFileResults: ImageCapture.OutputFileResults) {
                Toast.makeText(requireContext(), "picture saved: $path", Toast.LENGTH_LONG).show()
            }

            override fun onError(exception: ImageCaptureException) {
                Toast.makeText(requireContext(), "task picture error: $exception", Toast.LENGTH_LONG).show()
            }
        }
    )
}

指定照片存储位置，照片默认为JPEG格式
使用imageCapture.takePicture拍照并监听回调

录制视频

private fun startRecording() {
    var fileName = getFileName("mp4")

    val contentValues = ContentValues().apply {
        put(MediaStore.Video.Media.DISPLAY_NAME, fileName)
    }
    var mediaStoreOutput = MediaStoreOutputOptions.Builder(
        requireActivity().contentResolver,
        MediaStore.Video.Media.EXTERNAL_CONTENT_URI)
        .setContentValues(contentValues)
        .build()

    currentRecording = videoCapture.output
        .prepareRecording(requireActivity(), mediaStoreOutput)
        .start(mainThreadExecutor, captureListener)
}

private fun getFileName(type: String): String {
    var date = Date()
    var simpleDateFormat = SimpleDateFormat(FILENAME_FORMAT)

    return simpleDateFormat.format(date) + ".$type"
}

private val captureListener = Consumer<VideoRecordEvent> { event ->
    // TODO 视频状态监听处理
}