Lidl, the German supermarket, every year for a week sells a handlebar phone bag that works through its own protective plastic with the iPhone touch screen even when there is protective film over the iPhone screen to add another layer of Touch Insensitivity <TM>. It comes with a clip on the baggie side which separates the fastening to leave it on the bike, so that you can carry the phone in its baggie away with you and just clip it back in when you return to the bike. Works a treat for a few bucks.
I mention it because between the permanent part of the clip remaining on the bike and the spring loaded release on the baggie, the phone bag is raised about an inch, so controls that you don't need to see because you know what they do, can be under the baggie. For instance, the controls for my electric motor and the bell on my bike are half under the baggie.
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For bike phones I'm very keen on the iPhone 4S from 2011 and the SE from 2016 for their carved-from-solid-aluminium construction which can withstand endless hard handling, and also for their smaller size; the 2016 SE has the longest battery life of any of the reasonably sized iPhones. But I don't use the phone for navigation, instead using it to control my power output to the heart rate my cardiologist permits, filling in with the electric motor beyond that. For that the Crivit baggie from Lidl and the smaller iPhones are brilliant; even when I'm riding in a party which is generally slower, so that I'm not glancing at the phone every few seconds, Polar's Beat programme on the iPhone tells me aloud at every kilometre what my heartbeat is; the baggie does not impede the voice, so if your nav programme has voice responses, the size of the screen doesn't matter. I'm training Siri to say, "Hello, Big Boy, you're building muscles in places I especially appreciate."