Google Jetpack新组件CameraX介绍与实践

1    // CameraX
2    def camerax_version = "1.0.0-alpha01"
3    implementation "androidx.camera:camera-core:${camerax_version}"
4    implementation "androidx.camera:camera-camera2:${camerax_version}"

1// // Apply declared configs to CameraX using the same lifecycle owner
2CameraX.bindToLifecycle(
3               lifecycleOwner: this, preview, imageCapture, imageAnalyzer)

1// Unbinds all use cases from the lifecycle and removes them from CameraX.
2 CameraX.unbindAll()

1fun buildPreviewUseCase(): Preview {
 2    val previewConfig = PreviewConfig.Builder()
 3        // 宽高比
 4        .setTargetAspectRatio(aspectRatio)
 5        // 旋转
 6        .setTargetRotation(rotation)
 7        // 分辨率
 8        .setTargetResolution(resolution)
 9        // 前后摄像头
10        .setLensFacing(lensFacing)
11        .build()
12
13    // 创建 Preview 对象
14    val preview = Preview(previewConfig)
15    // 设置监听
16    preview.setOnPreviewOutputUpdateListener { previewOutput ->
17        // PreviewOutput 会返回一个 SurfaceTexture
18        cameraTextureView.surfaceTexture = previewOutput.surfaceTexture
19    }
20
21    return preview
22}

1preview.setOnPreviewOutputUpdateListener { previewOutput ->
 2    cameraTextureView.surfaceTexture = previewOutput.surfaceTexture
 3
 4    // Compute the center of preview (TextureView)
 5    val centerX = cameraTextureView.width.toFloat() / 2
 6    val centerY = cameraTextureView.height.toFloat() / 2
 7
 8    // Correct preview output to account for display rotation
 9    val rotationDegrees = when (cameraTextureView.display.rotation) {
10        Surface.ROTATION_0 -> 0
11        Surface.ROTATION_90 -> 90
12        Surface.ROTATION_180 -> 180
13        Surface.ROTATION_270 -> 270
14        else -> return@setOnPreviewOutputUpdateListener
15    }
16
17    val matrix = Matrix()
18    matrix.postRotate(-rotationDegrees.toFloat(), centerX, centerY)
19
20    // Finally, apply transformations to TextureView
21    cameraTextureView.setTransform(matrix)
22}

1fun buildImageAnalysisUseCase(): ImageAnalysis {
 2    // 分析器配置 Config 的建造者
 3    val analysisConfig = ImageAnalysisConfig.Builder()
 4        // 宽高比例
 5        .setTargetAspectRatio(aspectRatio)
 6        // 旋转
 7        .setTargetRotation(rotation)
 8        // 分辨率
 9        .setTargetResolution(resolution)
10        // 图像渲染模式
11        .setImageReaderMode(readerMode)
12        // 图像队列深度
13        .setImageQueueDepth(queueDepth)
14        // 设置回调的线程
15        .setCallbackHandler(handler)
16        .build()
17
18    // 创建分析器 ImageAnalysis 对象
19    val analysis = ImageAnalysis(analysisConfig)
20
21    // setAnalyzer 传入实现了 analyze 接口的类
22    analysis.setAnalyzer { image, rotationDegrees ->
23        // 可以得到的一些图像信息，参见 ImageProxy 类相关方法
24        val rect = image.cropRect
25        val format = image.format
26        val width = image.width
27        val height = image.height
28        val planes = image.planes
29    }
30
31    return analysis
32}

1fun buildImageCaptureUseCase(): ImageCapture {
 2    val captureConfig = ImageCaptureConfig.Builder()
 3        .setTargetAspectRatio(aspectRatio)
 4        .setTargetRotation(rotation)
 5        .setTargetResolution(resolution)
 6        .setFlashMode(flashMode)
 7        // 拍摄模式
 8        .setCaptureMode(captureMode)
 9        .build()
10
11    // 创建 ImageCapture 对象
12    val capture = ImageCapture(captureConfig)
13    cameraCaptureImageButton.setOnClickListener {
14        // Create temporary file
15        val fileName = System.currentTimeMillis().toString()
16        val fileFormat = ".jpg"
17        val imageFile = createTempFile(fileName, fileFormat)
18
19        // Store captured image in the temporary file
20        capture.takePicture(imageFile, object : ImageCapture.OnImageSavedListener {
21            override fun onImageSaved(file: File) {
22                // You may display the image for example using its path file.absolutePath
23            }
24
25            override fun onError(useCaseError: ImageCapture.UseCaseError, message: String, cause: Throwable?) {
26                // Display error message
27            }
28        })
29    }
30
31    return capture
32}