安卓CameraX的使用

如果要在安卓应用中操作相机，有三个库可以选：

1. Camera（已废弃）：Camera是安卓最早的包，目前已废弃，在Android 5.0（API 级别 21）的设备上操作相机可以选择该包，保证兼容性；
2. Camera2：Camera2在Android 5.0（API 级别 21）开始提供，用于替代Camera，相比Camera，在性能、灵活性等方面有优势，但是使用起来更复杂；
3. CameraX：CameraX是对Camera2的封装，是Jetpack的一个库，支持Android 5.0（API 级别 21）及更高版本。CameraX降低了操作相机的难度，大多数情况下，使用CameraX已足以完成需求，建议使用CameraX。

注：Jetpack是一个由多个库组成的套件，可帮助开发者遵循最佳做法、减少样板代码并编写可在各种Android版本和设备中一致运行的代码，让开发者可将精力集中于真正重要的编码工作。

谷歌的文档只提供了Kotlin的代码示例，根据Kotlin的代码示例和文档，本文提供Java的实现。

1. CameraX常见用例

您可以使用CameraX，借助名为“用例”的抽象概念与设备的相机进行交互。提供的用例如下：

• 预览（Preview）：在屏幕上查看相机画面；
• 图片分析（ImageAnalysis）：逐帧处理相机捕获到的每一帧画面；
• 图片拍摄（ImageCapture）：拍照；
• 视频拍摄（VideoCapture）：拍视频（和音频）。

CameraX允许同时使用Preview、VideoCapture、ImageAnalysis和ImageCapture各一个实例。此外：

• 每个用例都可以单独使用。例如，应用可以在不使用预览的情况下录制视频；
• 启用扩展后，只能保证能够使用ImageCapture和Preview的组合。根据OEM实现情况，可能无法同时添加ImageAnalysis；无法为VideoCapture用例启用扩展。如需了解详情，请参阅扩展参考文档；
• 对于某些相机而言，在较低分辨率模式下可以支持的组合，在较高的分辨率下将无法支持，这具体取决于相机的功能；
• 在相机硬件级别为FULL或更低的设备上，组合使用Preview、VideoCapture和ImageCapture或ImageAnalysis可能会迫使CameraX为Preview和VideoCapture复制相机的PRIV数据流。这种重复（称为数据流共享）可让您同时使用这些功能，但代价是增加了处理需求。因此，您可能会遇到略长的延迟时间和缩短的电池续航时间。

2. 代码实现

在build.gradle中添加相关依赖：

// camerax
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}"
implementation "androidx.camera:camera-video:${camerax_version}"
// 扩展，本文代码未使用
// implementation "androidx.camera:camera-extensions:${camerax_version}"

在AndroidManifest.xml添加相关权限：

<uses-permission android:name="android.permission.CAMERA"/>
<uses-permission android:name="android.permission.RECORD_AUDIO" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

添加布局文件activity_camerax_preview.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:fitsSystemWindows="true"><androidx.camera.view.PreviewViewandroid:id="@+id/camerax_preview_view"android:layout_width="match_parent"android:layout_height="match_parent" /><RelativeLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:layout_alignParentBottom="true"><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:orientation="vertical"><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:gravity="center"><Buttonandroid:id="@+id/camerax_flash"android:layout_width="110dp"android:layout_height="70dp"android:layout_marginStart="10dp"android:layout_marginTop="5dp"android:layout_marginEnd="10dp"android:layout_marginBottom="5dp"android:text="开灯" /><Buttonandroid:id="@+id/camerax_switch_camera"android:layout_width="110dp"android:layout_height="70dp"android:layout_marginStart="10dp"android:layout_marginTop="5dp"android:layout_marginEnd="10dp"android:layout_marginBottom="5dp"android:text="切换摄像头" /></LinearLayout><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:gravity="center"><Buttonandroid:id="@+id/camerax_image_capture_button"android:layout_width="110dp"android:layout_height="70dp"android:layout_marginStart="10dp"android:layout_marginTop="5dp"android:layout_marginEnd="10dp"android:layout_marginBottom="5dp"android:text="拍照" /><Buttonandroid:id="@+id/camerax_video_capture_button"android:layout_width="110dp"android:layout_height="70dp"android:layout_marginStart="10dp"android:layout_marginTop="5dp"android:layout_marginEnd="10dp"android:layout_marginBottom="5dp"android:text="开始录制" /><Buttonandroid:id="@+id/camerax_video_capture_pause_button"android:layout_width="110dp"android:layout_height="70dp"android:layout_marginStart="10dp"android:layout_marginTop="5dp"android:layout_marginEnd="10dp"android:layout_marginBottom="5dp"android:text="暂停录制"android:visibility="gone" /></LinearLayout></LinearLayout></RelativeLayout>
</RelativeLayout>

activity类：

package org.tao.hetools.activities;import android.Manifest;
import android.content.ContentValues;
import android.os.Build;
import android.os.Bundle;
import android.provider.MediaStore;
import android.util.Log;
import android.util.Size;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;import androidx.activity.ComponentActivity;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.camera.core.Camera;
import androidx.camera.core.CameraSelector;
import androidx.camera.core.ImageAnalysis;
import androidx.camera.core.ImageCapture;
import androidx.camera.core.ImageCaptureException;
import androidx.camera.core.Preview;
import androidx.camera.core.TorchState;
import androidx.camera.lifecycle.ProcessCameraProvider;
import androidx.camera.video.MediaStoreOutputOptions;
import androidx.camera.video.Quality;
import androidx.camera.video.QualitySelector;
import androidx.camera.video.Recorder;
import androidx.camera.video.Recording;
import androidx.camera.video.VideoCapture;
import androidx.camera.view.PreviewView;
import androidx.core.content.ContextCompat;import com.google.common.util.concurrent.ListenableFuture;import org.tao.hetools.R;
import org.tao.hetools.utils.PermissionUtils;import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Date;
import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executor;public class CameraxPreviewActivity extends ComponentActivity {private static final String TAG = "CameraxPreviewActivity";private static final SimpleDateFormat SIMPLE_DATE_FORMAT = new SimpleDateFormat("yyyyMMddHHmmssSSS");private static final Size SIZE = new Size(1080, 1920);private static final List<CameraSelector> CAMERAS = Arrays.asList(CameraSelector.DEFAULT_BACK_CAMERA,CameraSelector.DEFAULT_FRONT_CAMERA);private static final String START_RECORD = "开始录制";private static final String STOP_RECORD = "结束录制";private static final String PAUSE_RECORD = "暂停录制";private static final String RESUME_RECORD = "恢复录制";private PreviewView previewView;private Executor executor;private Preview preview;private ImageAnalysis imageAnalysis;private ImageCapture imageCapture;private VideoCapture<Recorder> videoCapture;private Recording videoRecording;private ProcessCameraProvider cameraProvider;private Camera camera;private boolean isRecordingStart = false;private boolean isRecordingPause = false;private int cameraIndex = 0;private Button flashButton;private Button pauseResumeVideoButton;private Button startShopVideoButton;private Button switchCameraButton;@Overrideprotected void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);this.setContentView(R.layout.activity_camerax_preview);PermissionUtils.checkPermission(this, Manifest.permission.CAMERA,Manifest.permission.RECORD_AUDIO,Manifest.permission.WRITE_EXTERNAL_STORAGE);previewView = findViewById(R.id.camerax_preview_view);executor = ContextCompat.getMainExecutor(this);initCamerax();initButton();}private void initCamerax() {// 可以将相机生命周期绑定到activity，从而免去打开、关闭相机的任务ListenableFuture<ProcessCameraProvider> cameraProviderListenableFuture = ProcessCameraProvider.getInstance(this);cameraProviderListenableFuture.addListener(() -> {try {cameraProvider = cameraProviderListenableFuture.get();// 预览preview = new Preview.Builder().build();preview.setSurfaceProvider(previewView.getSurfaceProvider());// 图片分析imageAnalysis = new ImageAnalysis.Builder()// 设置输出图片格式.setOutputImageFormat(ImageAnalysis.OUTPUT_IMAGE_FORMAT_YUV_420_888)// 非阻塞模式，只取最新的图片。若需要每帧图片都处理，使用阻塞模式 ImageAnalysis.STRATEGY_BLOCK_PRODUCER.setBackpressureStrategy(ImageAnalysis.STRATEGY_KEEP_ONLY_LATEST).setTargetResolution(SIZE).build();imageAnalysis.setAnalyzer(executor, (imageProxy) -> {// close后才认为处理完成当前帧，所以放到try-with-resources语句中try (imageProxy) {// 在此处处理图片，如对图片进行人脸、条码识别等Log.i(TAG, "接收到一帧图片" + SIMPLE_DATE_FORMAT.format(new Date()));} catch (Exception exception) {Log.w(TAG, exception.getMessage());}});// 拍照imageCapture = new ImageCapture.Builder().setFlashMode(ImageCapture.FLASH_MODE_AUTO).setTargetResolution(SIZE).build();// 录制Recorder recorder = new Recorder.Builder().setQualitySelector(QualitySelector.from(Quality.FHD)).build();videoCapture = VideoCapture.withOutput(recorder);cameraProvider.unbindAll();camera = cameraProvider.bindToLifecycle(this, CAMERAS.get(cameraIndex), preview,imageCapture, videoCapture);} catch (ExecutionException e) {throw new RuntimeException(e);} catch (InterruptedException e) {throw new RuntimeException(e);}}, executor);}private void initButton() {initFlashButton();initSwitchButton();initImageCaptureButton();initVideoCaptureButtons();}/*** 视频操作按钮*/private void initVideoCaptureButtons() {startShopVideoButton = findViewById(R.id.camerax_video_capture_button);pauseResumeVideoButton = findViewById(R.id.camerax_video_capture_pause_button);// 开始/停止录制视频startShopVideoButton.setOnClickListener(view -> {if (videoCapture == null || executor == null) {return;}if (isRecordingStart) {videoRecording.stop();videoRecording = null;isRecordingStart = false;startShopVideoButton.setText(START_RECORD);// 视频录制停止后不显示"暂停/恢复录制"按钮pauseResumeVideoButton.setVisibility(View.GONE);// 录制视频完成后显示切换摄像头按钮switchCameraButton.setVisibility(View.VISIBLE);return;}PermissionUtils.checkPermission(this, Manifest.permission.RECORD_AUDIO);videoRecording = videoCapture.getOutput().prepareRecording(this, getMediaStoreOutputOptions()).withAudioEnabled().start(executor, videoRecordEvent -> {});isRecordingStart = true;startShopVideoButton.setText(STOP_RECORD);pauseResumeVideoButton.setText(PAUSE_RECORD);// 视频录制开始后显示"暂停/恢复录制"按钮pauseResumeVideoButton.setVisibility(View.VISIBLE);// 录制视频期间不允许切换摄像头，切换摄像头会终止录制switchCameraButton.setVisibility(View.GONE);});// 暂停/恢复录制视频pauseResumeVideoButton.setOnClickListener(view -> {if (videoCapture == null || executor == null || videoRecording == null || !isRecordingStart) {return;}if (isRecordingPause) {isRecordingPause = false;videoRecording.resume();pauseResumeVideoButton.setText(PAUSE_RECORD);} else {videoRecording.pause();isRecordingPause = true;pauseResumeVideoButton.setText(RESUME_RECORD);}});}/*** 拍照按钮*/private void initImageCaptureButton() {findViewById(R.id.camerax_image_capture_button).setOnClickListener(view -> {if (imageCapture == null || executor == null) {return;}imageCapture.takePicture(getImageOutputFileOptions(), executor,new ImageCapture.OnImageSavedCallback() {@Overridepublic void onImageSaved(@NonNull ImageCapture.OutputFileResults outputFileResults) {Log.i(TAG, "save picture success");Toast.makeText(CameraxPreviewActivity.this, "success", Toast.LENGTH_SHORT).show();}@Overridepublic void onError(@NonNull ImageCaptureException exception) {Log.w(TAG, "error" + exception.getMessage());Toast.makeText(CameraxPreviewActivity.this, "fail", Toast.LENGTH_SHORT).show();}});});}/*** 切换摄像头按钮*/private void initSwitchButton() {switchCameraButton = findViewById(R.id.camerax_switch_camera);switchCameraButton.setOnClickListener((view -> {if (cameraProvider == null) {return;}if (++cameraIndex >= CAMERAS.size()) {cameraIndex = 0;}cameraProvider.unbindAll();cameraProvider.bindToLifecycle(this, CAMERAS.get(cameraIndex), preview, imageAnalysis,imageCapture, videoCapture);resetButtonStatus(cameraIndex);}));}/*** 闪光灯按钮*/private void initFlashButton() {flashButton = findViewById(R.id.camerax_flash);flashButton.setOnClickListener(view -> {if (camera == null) {return;}boolean isTorchOff = camera.getCameraInfo().getTorchState().getValue() == TorchState.OFF;camera.getCameraControl().enableTorch(isTorchOff);flashButton.setText(camera.getCameraInfo().getTorchState().getValue() == TorchState.ON ? "关灯" : "开灯");});}/*** 重设按钮状态*/private void resetButtonStatus(int cameraIndex) {flashButton.setText("开灯");flashButton.setVisibility(cameraIndex == 0 ? View.VISIBLE : View.GONE);startShopVideoButton.setText(START_RECORD);pauseResumeVideoButton.setText(PAUSE_RECORD);pauseResumeVideoButton.setVisibility(View.GONE);}private ImageCapture.OutputFileOptions getImageOutputFileOptions() {return new ImageCapture.OutputFileOptions.Builder(getContentResolver(), MediaStore.Images.Media.EXTERNAL_CONTENT_URI,getContentValues("image/png")).build();}private MediaStoreOutputOptions getMediaStoreOutputOptions() {return new MediaStoreOutputOptions.Builder(getContentResolver(),MediaStore.Video.Media.EXTERNAL_CONTENT_URI).setContentValues(getContentValues("video/mp4")).build();}private ContentValues getContentValues(String mimeType) {String name = SIMPLE_DATE_FORMAT.format(new Date());ContentValues contentValues = new ContentValues();contentValues.put(MediaStore.MediaColumns.DISPLAY_NAME, name);contentValues.put(MediaStore.MediaColumns.MIME_TYPE, mimeType);if (Build.VERSION.SDK_INT > Build.VERSION_CODES.P) {contentValues.put(MediaStore.Images.Media.RELATIVE_PATH, "Pictures/HeTools");}return contentValues;}
}

参考文章

1. 开始使用Android相机