I'm surprised no one has mentioned pttrns, yet. This website is incredible for mobile design as it can be sorted by OS, page type (e.g. onboarding, messaging), and even by device type (e.g. watch, tablet). The name pttrns is entirely appropriate, as you'll start to identify certain similarities across different camera designs, for instance, and have a better understanding for why certain elements are placed where they are. I use this a lot and it's worth subscribing for access to unlimited and the secret Slack.