视频采集：Android平台基于CameraX的实现

什么是CameraX（快乐星球）

       在 Android 应用中要实现 Camera 功能还是比较困难的，为了保证在各品牌手机设备上的兼容性、响应速度等体验细节，Camera 应用的开发者往往需要花很大的时间和精力进行测试，甚至需要手动在数百种不同设备上进行测试。CameraX 正是为解决这个痛点而诞生的。另外，CameraX 基于 Camera2 API 实现，它极大地简化了在 minSdk 21 及以上版本的实现过程。这篇文章为大家准备了CameraX的使用。
       个人使用过后感觉比Camera和Camera2 更加简单易用，且兼容性更好，不会出现常见的聚焦失败等问题。同样后面有完整代码。

有什么知识？

了解如何添加CameraX依赖项。
了解如何在活动中显示相机预览。（预览用例）
了解拍照后并将其保存到存储中。（ImageCapture用例）
了解如何实时分析相机中的帧。（ImageAnalysis用例）

需要什么？

Android设备。
Android Studio的模拟器也可以使用
我们建议使用R及更高版本。图像分析用例不适用于低于R的任何对象。
支持的最低API级别为21。
Android Studio 3.6或更高版本。

步骤

1、构建项目这里不说了

2、添加Gradle依赖

def camerax_version = "1.0.0-beta03"
// CameraX core library using camera2 implementation
implementation "androidx.camera:camera-camera2:$camerax_version"
// CameraX Lifecycle Library
implementation "androidx.camera:camera-lifecycle:$camerax_version"
// CameraX View class
implementation "androidx.camera:camera-view:1.0.0-alpha10"

使用CameraX中可能会用到Java8的方法，因此我们需要相应地设置编译选项。在该android块的末尾，紧接着buildTypes，添加以下内容：

compileOptions {sourceCompatibility JavaVersion.VERSION_1_8targetCompatibility JavaVersion.VERSION_1_8
}

3、XML布局

PreviewView内部是surface实现的 是一个TextureView

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical"android:layout_width="match_parent"android:layout_height="match_parent"><Buttonandroid:id="@+id/camera_capture_button"android:layout_width="100dp"android:layout_height="100dp"android:layout_marginBottom="50dp"android:scaleType="fitCenter"android:text="Take Photo"android:elevation="2dp" /><!--内部是surface实现的 是一个TextureView--><androidx.camera.view.PreviewViewandroid:id="@+id/viewFinder"android:layout_width="match_parent"android:layout_height="match_parent" />
</RelativeLayout>

4、申请权限

我们在AndroidManifest.xml中设置：

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

CameraXCapture.Java

private final String[] PERMISSIONS = new String[]{Manifest.permission.CAMERA,Manifest.permission.READ_EXTERNAL_STORAGE,Manifest.permission.WRITE_EXTERNAL_STORAGE};

OnCreate中

if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {ActivityCompat.requestPermissions(this, PERMISSIONS, 1);}

5、开启Camera和预览

public class CameraXCapture extends AppCompatActivity{private String TAG = "CameraXBasic";private String FILENAME_FORMAT = "yyyy-MM-dd-HH-mm-ss-SSS";private Preview preview = null;private ImageCapture imageCapture;//分析private ImageAnalysis imageAnalysis;private Camera camera = null;private File outputDirectory;private ExecutorService cameraExecutor;private PreviewView viewFinder;private final String[] PERMISSIONS = new String[]{Manifest.permission.CAMERA,Manifest.permission.READ_EXTERNAL_STORAGE,Manifest.permission.WRITE_EXTERNAL_STORAGE};@Overrideprotected void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_camerax_capture);if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {ActivityCompat.requestPermissions(this, PERMISSIONS, 1);}startCamera();viewFinder = findViewById(R.id.viewFinder);// Setup the listener for take photo buttonfindViewById(R.id.camera_capture_button).setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {//takePhoto();}});outputDirectory = getOutputDirectory();cameraExecutor = Executors.newSingleThreadExecutor();}/*** 开启预览*/private void startCamera() {//创建的实例ProcessCameraProvider。这用于将摄像机的生命周期绑定到生命周期所有者。// 由于CameraX具有生命周期感知功能，因此您不必担心打开和关闭相机。ListenableFuture<ProcessCameraProvider> cameraProviderFuture = ProcessCameraProvider.getInstance(this);//侦听器添加到中cameraProviderFuture。添加一个Runnable作为一个参数，// 稍后我们将对其进行填充。添加作为第二个参数，这将返回一个在主线程上运行的。// ContextCompat.getMainExecutor()ExecutorcameraProviderFuture.addListener(new Runnable() {@Overridepublic void run() {try {// Used to bind the lifecycle of cameras to the lifecycle owner//添加ProcessCameraProvider，用于将相机的生命周期绑定到应用程序进程中的LifecycleOwnerProcessCameraProvider cameraProvider = cameraProviderFuture.get();//Preview//初始化您的Preview对象。preview = new Preview.Builder().build(); // select cake camera//一个CameraSelector对象，然后使用该 CameraSelector.Builder.requireLensFacing方法传递您喜欢的镜头。CameraSelector cameraSelector = new CameraSelector.Builder().requireLensFacing(CameraSelector.LENS_FACING_FRONT).build();// Unbind use cases before rebindingcameraProvider.unbind();//Bind Use cases to camera//然后将cameraSelector和预览对象绑定到cameraProvider。// 将viewFinder的Surface提供程序附加到preview用例camera = cameraProvider.bindToLifecycle(CameraXCapture.this, cameraSelector, preview, imageCapture, imageAnalysis);preview.setSurfaceProvider(viewFinder.createSurfaceProvider(camera.getCameraInfo()));} catch (ExecutionException e) {e.printStackTrace();} catch (InterruptedException e) {e.printStackTrace();}}}, ContextCompat.getMainExecutor(this));}

6、完整代码带takePhoto拍照和实时数据帧数据

运行后，点击按钮可以看到提示，保存照片的路径。
查看命令行窗口logcat可以看到：(随时捕获的帧数据)

public class CameraXCapture extends AppCompatActivity{private String TAG = "CameraXBasic";private String FILENAME_FORMAT = "yyyy-MM-dd-HH-mm-ss-SSS";private Preview preview = null;private ImageCapture imageCapture;//分析private ImageAnalysis imageAnalysis;private Camera camera = null;private File outputDirectory;private ExecutorService cameraExecutor;private PreviewView viewFinder;private final String[] PERMISSIONS = new String[]{Manifest.permission.CAMERA,Manifest.permission.READ_EXTERNAL_STORAGE,Manifest.permission.WRITE_EXTERNAL_STORAGE};@Overrideprotected void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_camerax_capture);if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {ActivityCompat.requestPermissions(this, PERMISSIONS, 1);}startCamera();viewFinder = findViewById(R.id.viewFinder);// Setup the listener for take photo buttonfindViewById(R.id.camera_capture_button).setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {takePhoto();}});outputDirectory = getOutputDirectory();cameraExecutor = Executors.newSingleThreadExecutor();}/*** 开启预览*/private void startCamera() {//创建的实例ProcessCameraProvider。这用于将摄像机的生命周期绑定到生命周期所有者。// 由于CameraX具有生命周期感知功能，因此您不必担心打开和关闭相机。ListenableFuture<ProcessCameraProvider> cameraProviderFuture = ProcessCameraProvider.getInstance(this);//侦听器添加到中cameraProviderFuture。添加一个Runnable作为一个参数，// 稍后我们将对其进行填充。添加作为第二个参数，这将返回一个在主线程上运行的。// ContextCompat.getMainExecutor()ExecutorcameraProviderFuture.addListener(new Runnable() {@Overridepublic void run() {try {// Used to bind the lifecycle of cameras to the lifecycle owner//添加ProcessCameraProvider，用于将相机的生命周期绑定到应用程序进程中的LifecycleOwnerProcessCameraProvider cameraProvider = cameraProviderFuture.get();//Preview//初始化您的Preview对象。preview = new Preview.Builder().build();//创建imageCaptureimageCapture = new ImageCapture.Builder().build();//创建imageAnalyzerimageAnalysis = new ImageAnalysis.Builder().build();imageAnalysis.setAnalyzer(cameraExecutor, new LuminosityAnalyzer());// select cake camera//一个CameraSelector对象，然后使用该 CameraSelector.Builder.requireLensFacing方法传递您喜欢的镜头。CameraSelector cameraSelector = new CameraSelector.Builder().requireLensFacing(CameraSelector.LENS_FACING_FRONT).build();// Unbind use cases before rebindingcameraProvider.unbind();//Bind Use cases to camera//然后将cameraSelector和预览对象绑定到cameraProvider。// 将viewFinder的Surface提供程序附加到preview用例camera = cameraProvider.bindToLifecycle(CameraXCapture.this, cameraSelector, preview, imageCapture, imageAnalysis);preview.setSurfaceProvider(viewFinder.createSurfaceProvider(camera.getCameraInfo()));} catch (ExecutionException e) {e.printStackTrace();} catch (InterruptedException e) {e.printStackTrace();}}}, ContextCompat.getMainExecutor(this));}/*** 拍照*/private void takePhoto() {// Create timestamped output file to hold the imageFile photoFile = new File(outputDirectory, new SimpleDateFormat(FILENAME_FORMAT, Locale.US).format(System.currentTimeMillis()) + ".jpg");// Create output options object which contains file + metadataImageCapture.OutputFileOptions outputOptions = new ImageCapture.OutputFileOptions.Builder(photoFile).build();// Setup image capture listener which is triggered after photo has// been takenimageCapture.takePicture(outputOptions, ContextCompat.getMainExecutor(this), new ImageCapture.OnImageSavedCallback() {@Overridepublic void onImageSaved(@NonNull ImageCapture.OutputFileResults outputFileResults) {Uri uri = Uri.fromFile(photoFile);Toast.makeText(CameraXCapture.this, uri.toString(), Toast.LENGTH_SHORT).show();}@Overridepublic void onError(@NonNull ImageCaptureException exception) {Log.e(TAG, "Photo capture failed:die");}});}private File getOutputDirectory(){File file = new File(Environment.getExternalStorageDirectory(), "camerax");if (!file.exists()){file.mkdirs();}return file;}private class LuminosityAnalyzer implements ImageAnalysis.Analyzer{@Overridepublic void analyze(@NonNull ImageProxy image) {Log.e(TAG, "analyze: ...");image.close();}}
}