Doesn't sound familiar. I have been using the Snapdragon camera app quite a lot, and always with physical camera button. I can easily feel the difference between "focus" and "shutter". Of course the button feedback is nowhere near to a DSLR shutter button for example, but still performs quite good. I don't remember taking any photos accidentally without focusing it first. You should see the focusing ring on the screen to turn green when it has made the focusing successfully.