Some Android-specific settings

[davidhubbard]

The app currently blindly does this:

• Keep the screen on, and never go to sleep
• Hide status bar (top of screen)
• Hide nav bar (bottom of screen)
• If nav bar is shown by user swiping up, wait 2s and hide it again

It would be nice to give the user control:

• If the user leaves the app, the device will go to sleep, so they do have this level of control right now
• If the user's device is not plugged in, disable the "never go to sleep"
• Add a setting: "Stay awake" { "Always" | "When plugged in" | "Never" }
• Add a setting: "Nav Bar Mode" { "Auto Hide" | "Glass" | "Show" }
• Nav bar mode "Glass" just means using SYSTEM_UI_FLAG_IMMERSIVE_STICKY
• Add a setting: "Smart Nav Bar" { "On" | "Off" } so if the user swiped up to get the nav bar, then the nav bar disappeared 2 s later, then the user swiped up within 2 s after that, this is a "user frustration" moment. If the user has 2 "user frustration" moments with the nav bar auto-disappear code within 5 minutes, then "Smart Nav Bar" switches from "On" to "Off," and the nav bar is shown and does not auto-hide any more.

[davidhubbard]

These settings are Android-specific. While working on Bluetooth support, these settings came up:

• Always turn on Bluetooth
• ACTION_REQUEST_DISCOVERABLE is blindly turned on when discovering. This can be improved by exposing the bit through to the js app and making the device DISCOVERABLE when the bluetooth settings screen is shown.
• Android will not notify you when a device disappears, but you can poll it using fetchUuidsWithSdp()