Google made a change in Android 9 to improve battery life; now some app developers are steamed
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Several developers have posted complaints on Google's issue tracker website for Android (via Android Police). The problem is that starting with Android 9 Pie, Google has limited the number of times an app can perform Wi-Fi scans. Such scans are required by certain apps that perform indoor navigation, measure signal strength, analyze Wi-Fi coverage and more. For example, the developers of an app called ElectroSmart posted several complaints. The app measures the strength of different signals near phone users to help them limit their exposure to RF radiation.
"ElectroSmart is an app that shows the evolution of different signals (Wi-Fi, 2G, 3G, 4G, and Bluetooth) in realtime (updates the results every 5 seconds) when the app is run in foreground. It uses curves to represent this graphically. As such, the users of ElectroSmart who use the app in foreground expect the results to be updated in that frequency. Now with the new restrictions of Android Pie, the results shown to the user static after the four scans in 2-minute period are exhausted in the first 20 seconds of the use of the app. This makes the application a whole lot less useful."-Arnaud Legout, developer, ElectroSmart
Last summer, Google responded to the initial posts by saying that it needed to throttle Wi-Fi scanning in order to improve battery life and network performance on Android phones. One post suggested that Google allow users to whitelist certain apps; this would allow them to decide for themselves whether the functionality of a particular app is worth losing some battery life over. That would seem to be the best solution to this issue. After all, as this same post points out, smartphone users are willing to accept losing battery life when a GPS based navigation app is open.
Things that are NOT allowed: