一、声明必要的权限

在 Android 项目中，需要在AndroidManifest.xml文件中添加相机使用权限：

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

二、创建管理器

在 Java 或 Kotlin 代码中，创建一个CameraManager实例来管理相机设备：

  • 在java中:

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    CameraManager cameraManager = (CameraManager)getSystemService(Context.CAMERA_SERVICE);

  • 在Kotlin中:

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    val cameraManager = getSystemService(Context.CAMERA_SERVICE) as CameraManager

三、获取相机信息

查询相机列表，找到要打开的目标相机:

  • 在java中:

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             String[] cameraIds = cameraManager.getCameraIdList();
         String rearCameraId = null;
         for (String id : cameraIds) {
             CameraCharacteristics characteristics = cameraManager.getCameraCharacteristics(id);
             Integer facing = characteristics.get(CameraCharacteristics.LENS_FACING);
             if (facing!= null && facing == CameraCharacteristics.LENS_FACING_BACK) {
                 rearCameraId = id;
                 break;
             }
         }

  • 在Kotlin中:

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             val cameraIds = cameraManager.cameraIdList
         var rearCameraId: String? = null
         for (id in cameraIds) {
             val characteristics = cameraManager.getCameraCharacteristics(id)
             val facing = characteristics.get(CameraCharacteristics.LENS_FACING)
             if (facing!= null && facing == CameraCharacteristics.LENS_FACING_BACK) {
                 rearCameraId = id
                 break
             }
         }

四、打开相机

通过管理器，打开指定的相机:

  • 在java中:

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           CameraDevice.StateCallback stateCallback = new CameraDevice.StateCallback() {
           @Override
           public void onOpened(CameraDevice camera) {
               // 相机已打开，可以进行后续操作
           }

           @Override
           public void onDisconnected(CameraDevice camera) {
               camera.close();
           }

           @Override
           public void onError(CameraDevice camera, int error) {
               camera.close();
           }
       };
       cameraManager.openCamera(rearCameraId, stateCallback, null);

  • 在Kotlin中:

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           val stateCallback = object : CameraDevice.StateCallback() {
           override fun onOpened(camera: CameraDevice) {
               // 相机已打开，可以进行后续操作
           }

           override fun onDisconnected(camera: CameraDevice) {
               camera.close()
           }

           override fun onError(camera: CameraDevice, error: Int) {
               camera.close()
           }
       }
       cameraManager.openCamera(rearCameraId, stateCallback, null)

五、开启相机会话，并配置相机参数,获取YUV数据

打开相机成功后（在onOpened方法中），开始配置相机参数以获取 YUV 数据。

  • 在java中:

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           CameraDevice cameraDevice; // 已打开的相机设备
       CameraCaptureSession.StateCallback sessionCallback = new CameraCaptureSession.StateCallback() {
           @Override
           public void onConfigured(CameraCaptureSession session) {
               try {
                   CaptureRequest.Builder builder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
                   // 设置输出格式为YUV_420_888
                   builder.set(CaptureRequest.COLOR_CORRECTION_MODE, CaptureRequest.COLOR_CORRECTION_MODE_TRILINEAR);
                   ImageReader imageReader = ImageReader.newInstance(width, height, ImageFormat.YUV_420_888, 2);
                   imageReader.setOnImageAvailableListener(new ImageReader.OnImageAvailableListener() {
                       @Override
                       public void onImageAvailable(ImageReader reader) {
                           Image image = reader.acquireLatestImage();
                           if (image!= null) {
                               // 在这里处理YUV数据
                               ByteBuffer yBuffer = image.getPlanes()[0].getBuffer();
                               ByteBuffer uBuffer = image.getPlanes()[1].getBuffer();
                               ByteBuffer vBuffer = image.getPlanes()[2].getBuffer();
                               byte[] yData = new byte[yBuffer.remaining()];
                               byte[] uData = new byte[uBuffer.remaining()];
                               byte[] vData = new byte[vBuffer.remaining()];
                               yBuffer.get(yData);
                               uBuffer.get(uData);
                               vBuffer.get(vData);
                               image.close();
                           }
                       }
                   }, null);
                   builder.addTarget(imageReader.getSurface());
                   session.setRepeatingRequest(builder.build(), null, null);
               } catch (CameraAccessException e) {
                   e.printStackTrace();
               }
           }

           @Override
           public void onConfigureFailed(CameraCaptureSession session) {
               // 配置失败处理
           }
       };
       cameraDevice.createCaptureSession(Arrays.asList(imageReader.getSurface()), sessionCallback, null);

  • 在Kotlin中:

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           val cameraDevice: CameraDevice // 已打开的相机设备
       val sessionCallback = object : CameraCaptureSession.StateCallback() {
           override fun onConfigured(session: CameraCaptureSession) {
               try {
                   val builder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW)
                   // 设置输出格式为YUV_420_888
                   builder.set(CaptureRequest.COLOR_CORRECTION_MODE, CaptureRequest.COLOR_CORRECTION_MODE_TRILINEAR)
                   val imageReader = ImageReader.newInstance(width, height, ImageFormat.YUV_420_888, 2)
                   imageReader.setOnImageAvailableListener({ reader ->
                       val image = reader.acquireLatestImage()
                       if (image!= null) {
                           // 在这里处理YUV数据
                           val yBuffer = image.planes[0].buffer
                           val uBuffer = image.planes[1].buffer
                           val vBuffer = image.planes[2].buffer
                           val yData = ByteArray(yBuffer.remaining())
                           val uData = ByteArray(uBuffer.remaining())
                           val vData = ByteArray(vBuffer.remaining())
                           yBuffer.get(yData)
                           uBuffer.get(uData)
                           vBuffer.get(vData)
                           image.close()
                       }
                   }, null)
                   builder.addTarget(imageReader.surface)
                   session.setRepeatingRequest(builder.build(), null, null)
               } catch (e: CameraAccessException) {
                   e.printStackTrace()
               }
           }

           override fun onConfigureFailed(session: CameraCaptureSession) {
               // 配置失败处理
           }
       }
       cameraDevice.createCaptureSession(listOf(imageReader.surface), sessionCallback, null)

六、注意事项

  • 内存管理：在处理 YUV 数据时，要注意及时释放相关的ByteBuffer和Image对象，以避免内存泄漏。
  • 设备兼容性：不同的 Android 设备可能对Camera2 API 的支持存在差异，可能需要进行一些兼容性处理。
  • 性能优化：获取和处理 YUV 数据可能会消耗较多的系统资源，特别是在高分辨率或高帧率的情况下。可以根据实际需求调整相机参数（如分辨率、帧率等）来优化性能。