[Request]: Stream for Battery Level Changes #3733

Plugin

battery_plus

Use case

Currently, battery_plus only provides a Future for batteryLevel and a Stream for batteryState. To track level changes, developers are forced to use Timer.periodic to poll the getter, which is inefficient and not reactive.

Proposal

I would like to request a new stream: Stream onBatteryLevelChanged.

Platforms support this natively, so we should not need to rely on polling.

• iOS: We can observe UIDevice.batteryLevelDidChangeNotification. Note: Apple documentation states this notification is sent no more frequently than once per minute, which is acceptable for most use cases.
• Android: We can register a BroadcastReceiver for Intent.ACTION_BATTERY_CHANGED. This intent contains the EXTRA_LEVEL and EXTRA_SCALE to calculate the percentage immediately upon change.
• Web: The BatteryManager has a built-in event listener: onlevelchange.
• macOS: The system provides a system loop notification: kIOPSPowerSourceHaveToUpdateNotification

Something like:

// Current
Stream<BatteryState> get onBatteryStateChanged;

// Proposed
Stream<int> get onBatteryLevelChanged;

Additional Context

• This issue streamlines the battery level, but a stream to listen to all battery aspects would the preferrable solution. See [Request]: Support tracking all battery aspects #3446