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Sensor and system services

· 3 min read
Feodor Fitsner
Feodor Fitsner
Flet founder and developer

We've just merged a pull request introducing 10 new device and platform services to the Flet SDK, significantly expanding access to hardware sensors and system capabilities.

New sensor services​

  • Accelerometer – Reads raw acceleration along the X, Y, and Z axes, including gravity.
  • Barometer – Provides atmospheric pressure readings useful for altitude estimation.
  • Gyroscope – Measures device rotation around each axis.
  • Magnetometer – Detects magnetic field strength, commonly used for compass functionality.
  • UserAccelerometer – Reports acceleration data with gravity filtered out for cleaner motion detection.

New system services​

  • Battery – Monitors battery level, charging state, and power source changes.
  • Connectivity – Detects network status and connection type (Wi-Fi, mobile, offline).
  • ScreenBrightness – Allows reading and adjusting the device screen brightness.
  • Share – Invokes the system share sheet to share text, files, or URLs.
  • Wakelock – Prevents the device screen from dimming or sleeping while active.
Flet sensor and system services

Sensor services mostly work on iOS and Android devices. Using them in a web app is also possible to some extent, but only under specific browser and hardware conditions.

System services are supported on all mobile and desktop platforms.

How to test​

Install the latest Flet 0.70.0.devXYZ pre-release.

Use the flet debug command to run your app on a real iOS/Android device or emulator.

Testing in the Android emulator is especially convenient, as it allows you to experiment with virtually all available sensors:

Flet sensors testing in Android emulator

Services API​

Previously, some services were exposed as page properties, such as page.clipboard or page.shared_preferences.

All services are now standalone and should be used by creating their own instances. For example:

clipboard = ft.Clipboard()
await clipboard.set("Hello, world!")

or simply:

await ft.Clipboard().set("Hello, world!")

When you create a new instance of a service, it is automatically registered within the page and disposed of when it is no longer referenced - for example, at the end of a method call.

However, if you need to assign an event handler to a service that must persist across method calls, you must keep a reference to that service to prevent it from being disposed.

In an imperative Flet app, you can use the page.services list, which holds service instances. For example:

async def main(page: ft.Page):
    battery = ft.Battery()
    page.services.append(battery)  # need to keep a reference to the service

    async def on_state_change(e: ft.BatteryStateChangeEvent):
        print(f"State changed: {e.state}")

    battery.on_state_change = on_state_change

    ...

In a declarative Flet app, you can use the use_ref or use_state hook to hold a service reference. For example:

import flet as ft

@ft.component
def App():
    async def on_state_change(e: ft.BatteryStateChangeEvent):
        print(f"State changed: {e.state}")

    ft.use_ref(lambda: ft.Battery(on_state_change=on_state_change))

    return ft.Text("Battery status app")

ft.run(lambda page: page.render(App))

That's all for today, folks! Happy Fletting!