Setting Parameters.FLASH_MODE_TORCH doesn't work on Droid X 2.3

Question

I am writing an app that sets the flash mode to torch. I have been testing the application on my Droid X, and the LED light does not come on. I tried it on a Droid Incredible and it worked fine. I can't figure out what the problem is. Here is part of my code for turning on torch mode.

    Camera mCamera = Camera.open();
    Camera.Parameters params = mCamera.getParameters();
    if(params.getFlashMode() != null){
        params.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH);
    }
    mCamera.setParameters(params);

I have added mCamera.startPreview(); because I read that should make a difference, but it doesn't. I also made a list of available flash modes and displayed them to the screen to make sure that my Droid X does have torch mode, and it was in the list. I even created a new application from code I found online that turns the LED flash on and off with a button. Again it worked fine on the Droid Incredible but not the Droid X. Is there something I am missing to get this to run on the Droid X, or could it be something with Gingerbread? The Droid X is running Gingerbread and the Droid Incredible is running FroYo.

Answer 1

There are quite a few quirks when setting FLASH_MODE_TORCH.

Often you need to start a camera preview:

Camera mCamera = Camera.open();
mCamera.startPreview();
Camera.Parameters params = mCamera.getParameters();
if(params.getFlashMode() != null){
    params.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH);
}
mCamera.setParameters(params);

That may resolve it on some phones, other phones also require the preview to be drawn to a SurfaceView. This can be done by implementing SurfaceHolder.Callback interface in your activity. See an example here.