Android CameraX 使用指南及一些高级功能(简化相机开发)

def camerax_version = "1.3.0"
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}"

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

private val requestPermissionLauncher = registerForActivityResult(
    ActivityResultContracts.RequestPermission()
) { isGranted ->
    if (isGranted) {
        startCamera()
    } else {
        Toast.makeText(this, "Permission denied", Toast.LENGTH_SHORT).show()
    }
}
// 检查并请求权限
if (ContextCompat.checkSelfPermission(
        this, Manifest.permission.CAMERA
    ) == PackageManager.PERMISSION_GRANTED
) {
    startCamera()
} else {
    requestPermissionLauncher.launch(Manifest.permission.CAMERA)
}

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

private fun startCamera() {
    val cameraProviderFuture = ProcessCameraProvider.getInstance(this)
    cameraProviderFuture.addListener({
        // 用于绑定相机生命周期
        val cameraProvider: ProcessCameraProvider = cameraProviderFuture.get()
        // 预览
        val preview = Preview.Builder()
            .build()
            .also {
                it.setSurfaceProvider(viewFinder.surfaceProvider)
            }
        // 选择后置摄像头
        val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA
        try {
            // 解绑之前的所有用例
            cameraProvider.unbindAll()
            // 绑定用例到生命周期
            cameraProvider.bindToLifecycle(
                this, cameraSelector, preview
            )
        } catch(exc: Exception) {
            Log.e(TAG, "Use case binding failed", exc)
        }
    }, ContextCompat.getMainExecutor(this))
}

val imageAnalysis = ImageAnalysis.Builder()
    .setBackpressureStrategy(ImageAnalysis.STRATEGY_KEEP_ONLY_LATEST)
    .build()
imageAnalysis.setAnalyzer(executor) { imageProxy ->
    // 在这里处理图像
    val rotationDegrees = imageProxy.imageInfo.rotationDegrees
    // 处理完成后关闭imageProxy
    imageProxy.close()
}
// 记得在bindToLifecycle中添加这个用例
cameraProvider.bindToLifecycle(
    this, cameraSelector, preview, imageAnalysis
)

private fun takePhoto() {
    // 创建图片捕获用例
    val imageCapture = ImageCapture.Builder()
        .setCaptureMode(ImageCapture.CAPTURE_MODE_MINIMIZE_LATENCY)
        .build()
    // 绑定用例
    cameraProvider.bindToLifecycle(
        this, cameraSelector, preview, imageCapture
    )
    // 创建输出选项
    val outputOptions = ImageCapture.OutputFileOptions.Builder(
        File(externalMediaDirs.first(), "${System.currentTimeMillis()}.jpg")
    ).build()
    // 拍照
    imageCapture.takePicture(
        outputOptions,
        ContextCompat.getMainExecutor(this),
        object : ImageCapture.OnImageSavedCallback {
            override fun onError(exc: ImageCaptureException) {
                Log.e(TAG, "Photo capture failed: ${exc.message}", exc)
            }
            override fun onImageSaved(output: ImageCapture.OutputFileResults) {
                val savedUri = output.savedUri ?: Uri.fromFile(outputOptions.outputFile)
                Log.d(TAG, "Photo capture succeeded: $savedUri")
            }
        }
    )
}

val cameraInfo = cameraProvider.availableCameraInfos.find {
    it.cameraSelector == cameraSelector
}
// 检查闪光灯支持
val hasFlash = cameraInfo?.torchState?.value != null
// 检查变焦支持
val hasZoom = cameraInfo?.zoomState?.value != null