I am trying to get a full screen preview of the camera. I read through the documentation of camera2 which says Each Surface has to be pre-configured with an appropriate size and format (if applicable) to match the sizes and formats available from the camera device. Here is what I understand so far. Please correct me if any of my understanding is wrong:
The texture view and the preview buffer need to be the same aspect ratio. They can be different resolutions, but the aspect ratio must be the same if you don't want the preview to look distorted.
You should set the buffer size of the texture view to the optimally chosen preview size. camera2basic demo seems to confirm this with the line texture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight().
The question I have is, once you match the aspect ratio and size of the texture view and the preview to be the same, how do you scale the texture view so that it fits fullscreen?
The camera2basic demo's configureTransform method seems to transform the TextureView to the preview size, but not make it full screen. How do I calculate the correct scale factor to make TextureView fullscreen?
You can just make your TextureView fill the screen in your Activity's layout. You'll then need to adjust the configureTransform() method to account for the aspect ratio difference between the full-screen TextureView and the closest-aspect preview size; basically you need to implement the usual letter- or pillar-boxing effect.
Of course, if there does happen to be a matching aspect ratio, you can use it directly, but this isn't too likely.