How does one retrieve the cameraID and use setTorchMode?

问题

So Android M recently came out and it now has a built in cameralight function called setTorchMode. I was curious as to how this worked as the parameters are (String cameraID, Boolean true/false). The Boolean obviously dictates whether the light is on or off, but how do you get the cameraID? I know there's a method called getCameraIDList, but that returns an array of IDs, not just one. How do you know which one in that list to use?

回答1:

You should use CameraManager "getCameraIdList" function which will retrieve you a list of strings where each represent an active camera.

回答2:

 if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
        mCameraManager = (CameraManager) context.getSystemService(Context.CAMERA_SERVICE);
        try {
            for (String camID : mCameraManager.getCameraIdList()) {
                CameraCharacteristics cameraCharacteristics = mCameraManager.getCameraCharacteristics(camID);
                int lensFacing = cameraCharacteristics.get(CameraCharacteristics.LENS_FACING);
                if (lensFacing == CameraCharacteristics.LENS_FACING_FRONT && cameraCharacteristics.get(CameraCharacteristics.FLASH_INFO_AVAILABLE)) {
                    mCameraId = camID;
                    break;
                } else if (lensFacing == CameraCharacteristics.LENS_FACING_BACK && cameraCharacteristics.get(CameraCharacteristics.FLASH_INFO_AVAILABLE)) {
                    mCameraId = camID;
                }
            }
            if (mCameraId != null) {
                mCameraManager.setTorchMode(mCameraId, true);
            }
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

mCameraId will turn on front camera flash if available or else back camera flash if available. If no flash is available then mCameraId will be null and setTorchMode will not be called.

来源：https://stackoverflow.com/questions/32304341/how-does-one-retrieve-the-cameraid-and-use-settorchmode