Barometer

Streams barometer readings (atmospheric pressure in hPa). Useful for altitude calculations and weather-related experiences.

Note

• Supported platforms: Android, iOS.
• Barometer APIs are not exposed on the web or desktop platforms.
• iOS ignores custom sampling intervals.

Running on iOS

On iOS you must also include a key called NSMotionUsageDescription in your app's Info.plist file. This key provides a message that tells the user why the app is requesting access to the device's motion data. Barometer service needs access to motion data to get barometer data.

For example, add the following to your pyproject.toml file:

[tool.flet.ios.info]
NSMotionUsageDescription = "This app requires access to the barometer to provide altitude information."

Adding NSMotionUsageDescription is a requirement and not doing so will crash your app when it attempts to access motion data.

Inherits: Service

Properties

• cancel_on_error(bool) –

  Whether the stream subscription should cancel on the first sensor error.

• enabled(bool) –

  Whether the sensor should be sampled. Disable to stop streaming.

• interval(Duration | None) –

  Desired sampling interval provided as a Duration.

Events

• on_error(EventHandler[SensorErrorEvent] | None) –

  Fired when the platform reports a sensor error. event.message is the error

• on_reading(EventHandler[BarometerReadingEvent] | None) –

  Fires when a new reading is available.

Examples

import flet as ft


def main(page: ft.Page):
    intro = ft.Text("Atmospheric pressure (hPa).")
    reading = ft.Text("Waiting for data...")

    def handle_reading(e: ft.BarometerReadingEvent):
        reading.value = f"{e.pressure:.2f} hPa"
        page.update()

    def handle_error(e: ft.SensorErrorEvent):
        page.add(ft.Text(f"Barometer error: {e.message}"))

    page.services = [
        ft.Barometer(
            on_reading=handle_reading,
            on_error=handle_error,
            interval=ft.Duration(milliseconds=500),
        ),
    ]

    page.controls = [intro, reading]


ft.run(main)

Properties

cancel_on_error class-attribute instance-attribute

cancel_on_error: bool = True

Whether the stream subscription should cancel on the first sensor error.

enabled class-attribute instance-attribute

enabled: bool = True

Whether the sensor should be sampled. Disable to stop streaming.

interval class-attribute instance-attribute

interval: Duration | None = None

Desired sampling interval provided as a Duration. Defaults to 200 ms, though some platforms (such as iOS) ignore custom sampling intervals.

Events

on_error class-attribute instance-attribute

on_error: EventHandler[SensorErrorEvent] | None = None

Fired when the platform reports a sensor error. event.message is the error description.

on_reading class-attribute instance-attribute

on_reading: EventHandler[BarometerReadingEvent] | None = (
    None
)

Fires when a new reading is available.

event contains pressure (hPa) and timestamp (microseconds since epoch).