4-4.Android Camera 之简化编码模板（获取摄像头 ID、选择最优预览尺寸）

一、Camera 简化思路

1. 在 Camera 的开发中，其实我们通常只关注打开相机、图像预览和关闭相机，其他的步骤我们不应该花费太多的精力

2. 为此，应该提供一个工具类，它有处理相机的一些基本工具方法，包括获取摄像头 ID、选择最优预览尺寸以及打印相机参数信息

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二、Camera 工具类

• CameraIdResult.java

public class CameraIdResult {private int qzCameraId = -1; // 前置摄像头 idprivate int hzCameraId = -1; // 后置摄像头 idpublic CameraIdResult() {}public CameraIdResult(int qzCameraId, int hzCameraId) {this.qzCameraId = qzCameraId;this.hzCameraId = hzCameraId;}public int getQzCameraId() {return qzCameraId;}public void setQzCameraId(int qzCameraId) {this.qzCameraId = qzCameraId;}public int getHzCameraId() {return hzCameraId;}public void setHzCameraId(int hzCameraId) {this.hzCameraId = hzCameraId;}
}

• MyCameraTool.java

public class MyCameraTool {public static final String TAG = MyCameraTool.class.getSimpleName();/*** 得到摄像头 Id 对象** @return 摄像头 Id 对象，它有前置摄像头 Id 和后置摄像头 Id*/public static CameraIdResult getCameraIdResult() {CameraIdResult cameraIdResult = new CameraIdResult();int numberOfCameras = Camera.getNumberOfCameras();Log.i(TAG, "------------------------------ 摄像头个数：" + numberOfCameras);for (int cameraId = 0; cameraId < numberOfCameras; cameraId++) {Camera.CameraInfo cameraInfo = new Camera.CameraInfo();Camera.getCameraInfo(cameraId, cameraInfo);if (cameraInfo.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {Log.i(TAG, "------------------------------ 前置摄像头，cameraId 为：" + cameraId);cameraIdResult.setQzCameraId(cameraId);}if (cameraInfo.facing == Camera.CameraInfo.CAMERA_FACING_BACK) {Log.i(TAG, "------------------------------ 后置摄像头，cameraId 为：" + cameraId);cameraIdResult.setHzCameraId(cameraId);} else {Log.i(TAG, "------------------------------ 其他摄像头，cameraId 为：" + cameraId);}}return cameraIdResult;}/*** 根据 SurfaceView 的尺寸和相机支持的预览尺寸来选择最优的预览尺寸** @param sizes 相机支持的预览尺寸列表* @param w     SurfaceView 的宽度* @param h     SurfaceView 的高度* @return 最优的预览尺寸，如果没有合适的尺寸则返回 null*/public static Camera.Size getOptimalPreviewSize(List<Camera.Size> sizes, int w, int h) {if (sizes == null) return null;final double ASPECT_TOLERANCE = 0.1;double targetRatio = (double) h / w;Camera.Size optimalSize = null;double minDiff = Double.MAX_VALUE;int targetHeight = h;// 遍历所有支持的预览尺寸for (Camera.Size size : sizes) {// 检查宽高比是否接近目标宽高比double ratio = (double) size.width / size.height;if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE) continue;// 计算当前尺寸与目标尺寸的宽度差异// 如果差异小于当前最小差异，则更新最优尺寸和最小差异if (Math.abs(size.height - targetHeight) < minDiff) {optimalSize = size;minDiff = Math.abs(size.height - targetHeight);}}// 如果找不到接近目标宽高比的尺寸，则选择最接近目标高度的尺寸if (optimalSize == null) {minDiff = Double.MAX_VALUE;for (Camera.Size size : sizes) {if (Math.abs(size.height - targetHeight) < minDiff) {optimalSize = size;minDiff = Math.abs(size.height - targetHeight);}}}return optimalSize;}/*** 打印相机参数信息** @param parameters 相机参数对象*/public static void showParameters(Camera.Parameters parameters) {Camera.Size previewSize = parameters.getPreviewSize();Log.i(TAG, "============================== getPreviewSize");Log.i(TAG, "---------- " + previewSize.width + " - " + previewSize.height);List<Camera.Size> supportedPreviewSizes = parameters.getSupportedPreviewSizes();Log.i(TAG, "============================== supportedPreviewSizes");Log.i(TAG, "============================== supportedPreviewSizes size: " + supportedPreviewSizes.size());for (Camera.Size supportedPreviewSize : supportedPreviewSizes) {Log.i(TAG, "---------- " + supportedPreviewSize.width + " - " + supportedPreviewSize.height);}Camera.Size pictureSize = parameters.getPictureSize();Log.i(TAG, "============================== getPictureSize");Log.i(TAG, "---------- " + pictureSize.width + " - " + pictureSize.height);List<Camera.Size> supportedPictureSizes = parameters.getSupportedPictureSizes();Log.i(TAG, "============================== getSupportedPictureSizes");Log.i(TAG, "============================== getSupportedPictureSizes: " + supportedPictureSizes.size());for (Camera.Size supportedPictureSize : supportedPictureSizes) {Log.i(TAG, "---------- " + supportedPictureSize.width + " - " + supportedPictureSize.height);}String focusMode = parameters.getFocusMode();Log.i(TAG, "============================== getFocusMode");Log.i(TAG,"---------- " + focusMode);String whiteBalance = parameters.getWhiteBalance();Log.i(TAG, "============================== getWhiteBalance");Log.i(TAG,"---------- " + whiteBalance);int exposureCompensation = parameters.getExposureCompensation();Log.i(TAG, "============================== getExposureCompensation");Log.i(TAG,"---------- " + exposureCompensation);String flashMode = parameters.getFlashMode();Log.i(TAG, "============================== getFlashMode");Log.i(TAG,"---------- " + flashMode);}
}

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三、Camera 工具类解析

1、获取取摄像头 ID

1. 该方法用于获取取摄像头 ID，它会返回一个 cameraIdResult 对象

2. cameraIdResult 对象有两个属性为 qzCameraId 和 hzCameraId，分别代表前置摄像头 ID 和后置摄像头 ID，如果 qzCameraId 或 hzCameraId 的值为 -1，代表没有获取到

public static CameraIdResult getCameraIdResult() {CameraIdResult cameraIdResult = new CameraIdResult();int numberOfCameras = Camera.getNumberOfCameras();Log.i(TAG, "------------------------------ 摄像头个数：" + numberOfCameras);for (int cameraId = 0; cameraId < numberOfCameras; cameraId++) {Camera.CameraInfo cameraInfo = new Camera.CameraInfo();Camera.getCameraInfo(cameraId, cameraInfo);if (cameraInfo.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {Log.i(TAG, "------------------------------ 前置摄像头，cameraId 为：" + cameraId);cameraIdResult.setQzCameraId(cameraId);}if (cameraInfo.facing == Camera.CameraInfo.CAMERA_FACING_BACK) {Log.i(TAG, "------------------------------ 后置摄像头，cameraId 为：" + cameraId);cameraIdResult.setHzCameraId(cameraId);} else {Log.i(TAG, "------------------------------ 其他摄像头，cameraId 为：" + cameraId);}}return cameraIdResult;
}

2、选择最优预览图像尺寸

• 该方法用于选择最优预览图像尺寸，设置最优预览图像尺寸，能保证在预览图像时（例如，SurfaceView）图像不被拉伸

public static Camera.Size getOptimalPreviewSize(List<Camera.Size> sizes, int w, int h) {if (sizes == null) return null;final double ASPECT_TOLERANCE = 0.1;double targetRatio = (double) h / w;Camera.Size optimalSize = null;double minDiff = Double.MAX_VALUE;int targetHeight = h;// 遍历所有支持的预览尺寸for (Camera.Size size : sizes) {// 检查宽高比是否接近目标宽高比double ratio = (double) size.width / size.height;if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE) continue;// 计算当前尺寸与目标尺寸的宽度差异// 如果差异小于当前最小差异，则更新最优尺寸和最小差异if (Math.abs(size.height - targetHeight) < minDiff) {optimalSize = size;minDiff = Math.abs(size.height - targetHeight);}}// 如果找不到接近目标宽高比的尺寸，则选择最接近目标高度的尺寸if (optimalSize == null) {minDiff = Double.MAX_VALUE;for (Camera.Size size : sizes) {if (Math.abs(size.height - targetHeight) < minDiff) {optimalSize = size;minDiff = Math.abs(size.height - targetHeight);}}}return optimalSize;
}

3、打印相机参数信息

• 该方法用于打印相机参数信息，用于了解设备，并根据业务做更合适的设置

1. 例如，根据 supportedPreviewSizes 可以对预览图像的大小做更合适的设置（SurfaceView、setPreviewSize 方法）

2. 再例如，根据 getSupportedPictureSizes 可以对拍照时图片的大小做更合适的设置（setPictureSize 方法）

public static void showParameters(Camera.Parameters parameters) {Camera.Size previewSize = parameters.getPreviewSize();Log.i(TAG, "============================== getPreviewSize");Log.i(TAG, "---------- " + previewSize.width + " - " + previewSize.height);List<Camera.Size> supportedPreviewSizes = parameters.getSupportedPreviewSizes();Log.i(TAG, "============================== supportedPreviewSizes");Log.i(TAG, "============================== supportedPreviewSizes size: " + supportedPreviewSizes.size());for (Camera.Size supportedPreviewSize : supportedPreviewSizes) {Log.i(TAG, "---------- " + supportedPreviewSize.width + " - " + supportedPreviewSize.height);}Camera.Size pictureSize = parameters.getPictureSize();Log.i(TAG, "============================== getPictureSize");Log.i(TAG, "---------- " + pictureSize.width + " - " + pictureSize.height);List<Camera.Size> supportedPictureSizes = parameters.getSupportedPictureSizes();Log.i(TAG, "============================== getSupportedPictureSizes");Log.i(TAG, "============================== getSupportedPictureSizes: " + supportedPictureSizes.size());for (Camera.Size supportedPictureSize : supportedPictureSizes) {Log.i(TAG, "---------- " + supportedPictureSize.width + " - " + supportedPictureSize.height);}String focusMode = parameters.getFocusMode();Log.i(TAG, "============================== getFocusMode");Log.i(TAG,"---------- " + focusMode);String whiteBalance = parameters.getWhiteBalance();Log.i(TAG, "============================== getWhiteBalance");Log.i(TAG,"---------- " + whiteBalance);int exposureCompensation = parameters.getExposureCompensation();Log.i(TAG, "============================== getExposureCompensation");Log.i(TAG,"---------- " + exposureCompensation);String flashMode = parameters.getFlashMode();Log.i(TAG, "============================== getFlashMode");Log.i(TAG,"---------- " + flashMode);
}