Android app开发：Camera2 api判断前后摄

public static final int LENS_FACING_FRONT_ID = 0;
public static final int LENS_FACING_BACK_ID = 1;

private int judgeCameraId() {
    int ret = 2;
    try {
        CameraManager cameraManager = (CameraManager) getSystemService(CAMERA_SERVICE);
        String[] cameraIdList = cameraManager.getCameraIdList();
        Log.d(TAG, "wjz debug judgeCameraId: cameraIdList.length is " + cameraIdList.length);
        switch (cameraIdList.length) {
            case 0:
                Log.e(TAG, "wjz debug judgeCameraId: 当前没有可用摄像头!!!!");
                ret = -1;
                break;
            case 1:
                //只有一个摄像头的时候，无论接前摄还是后摄，id都是0，因此通过LENS_FACING来判断摄像头的位置
                //camera2 api里面，0表示摄像头接在前摄，1表示摄像头接在后摄
                int face = cameraManager.getCameraCharacteristics(cameraIdList[0]).get(CameraCharacteristics.LENS_FACING);
                if (face == LENS_FACING_FRONT_ID) {
                    ret = LENS_FACING_FRONT_ID;
                    Log.d(TAG, "wjz debug judgeCameraId: 当前只有1个前摄像头");
                }
                if (face == LENS_FACING_BACK_ID) {
                    ret = LENS_FACING_BACK_ID;
                    Log.d(TAG, "wjz debug judgeCameraId: 当前只有1个后摄像头");
                }
                break;
            case 2:
                Log.d(TAG, "wjz debug judgeCameraId: 当前有2个可用摄像头！");
                break;
            default:
                break;
        }
    } catch (CameraAccessException e) {
        Log.e(TAG, "wjz debug judgeCameraId: error is " + e.getMessage());
        e.printStackTrace();
    }
    return ret;
}