目前Camera API 1使用的比较少了，一般代码如下。遇到的问题是camera1接口无法打开相机，cam2接口打开正常。最后排查结果是 sensor的 frameRate 配置不对。

    Camera camera;CameraPreview mPreview;@SuppressLint("MissingPermission")@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.cam_1_layout);mPreview = findViewById(R.id.camera_1_preview);try {camera = Camera.open(0);mPreview.setCamera(camera);} catch (Exception e) {e.printStackTrace();}}public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {private Camera mCamera;public CameraPreview(Context context, AttributeSet attrs) {super(context, attrs);}public CameraPreview(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);}public CameraPreview(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {super(context, attrs, defStyleAttr, defStyleRes);}public void setCamera(Camera camera) {mCamera = camera;}@Overridepublic void surfaceCreated(SurfaceHolder holder) {try {mCamera.setPreviewDisplay(holder);mCamera.startPreview();} catch (IOException e) {e.printStackTrace();}}@Overridepublic void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {// 相机预览尺寸变化时，调整相机参数if (mCamera != null) {Camera.Parameters parameters = mCamera.getParameters();parameters.setPreviewSize(width, height);mCamera.setParameters(parameters);}}@Overridepublic void surfaceDestroyed(SurfaceHolder holder) {// 停止相机预览并释放资源if (mCamera != null) {mCamera.stopPreview();mCamera.release();mCamera = null;}}

    log显示是  Camera.open(0); 时异常，预览分辨率不对导致。跟踪代码，Cam初始化时

CameraService::connectHelper 函数中执行 client->initialize，client 对应到不同api创建不同的对象。api1下的Camera2Client::initialize 流程中有 mParameters.initialize 步骤，在 Parameters::initialize 中执行 getFilteredSizes 进行过滤操作

    //过滤预览sizeres = getFilteredSizes(maxPreviewSize, &availablePreviewSizes);if (res != OK) return res;res = getFilteredSizes(videoSizeUpperBound, &availableVideoSizes);if (res != OK) return res;status_t Parameters::getFilteredSizes(Size limit, Vector<Size> *sizes) {if (info == NULL) {ALOGE("%s: Static metadata is not initialized", __FUNCTION__);return NO_INIT;}if (sizes == NULL) {ALOGE("%s: Input size is null", __FUNCTION__);return BAD_VALUE;}sizes->clear();Vector<StreamConfiguration> scs = getStreamConfigurations();for (size_t i=0; i < scs.size(); i++) {const StreamConfiguration &sc = scs[i];if (sc.isInput == ANDROID_SCALER_AVAILABLE_STREAM_CONFIGURATIONS_OUTPUT &&sc.format == HAL_PIXEL_FORMAT_IMPLEMENTATION_DEFINED &&sc.width <= limit.width && sc.height <= limit.height) {int64_t minFrameDuration = getMinFrameDurationNs({sc.width, sc.height}, HAL_PIXEL_FORMAT_IMPLEMENTATION_DEFINED);if (minFrameDuration > MAX_PREVIEW_RECORD_DURATION_NS) {// Filter slow sizes from preview/recordcontinue;}sizes->push({sc.width, sc.height});}}if (sizes->isEmpty()) {ALOGE("generated preview size list is empty!!");return BAD_VALUE;}return OK;
}

这里获取 sensor 配置支持的 ANDROID_SCALER_AVAILABLE_MIN_FRAME_DURATIONS 数值，与平台默认 MAX_PREVIEW_RECORD_DURATION_NS 值比较。这里比较是每一帧的时间，单位是ns，值越大，说明帧率越低。MAX_PREVIEW_RECORD_DURATION_NS 由系统默认设置，一般平台帧率30，MAX_PREVIEW_RECORD_DURATION_NS  = 1/30 * 1000 000 000 (ns)。sensor 配置帧率一般在 sensor.xml 中，标签是 <frameRate> ，根据不同SIZE会配置不同frameRate的值。