Barometer

**Overview**

Provides atmospheric pressure readings in hPa.

Use cases include altitude calculations and weather-related features.

**Platform Support**

**Supported:** Android, iOS.

**Not Supported:** Web, Desktop.

**iOS Specific:** Custom sampling intervals are ignored.

**iOS Configuration Requirement**

To access motion data on iOS, add NSMotionUsageDescription to your pyproject.toml file.

Example:

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

Failure to include this will cause the app to crash when accessing motion data.

**Inheritance**

Inherits from flet.Service.

**Properties**

cancel_on_error: bool

- Default: True - Description: Determines if the stream subscription should be cancelled upon encountering the first sensor error.

enabled: bool

- Default: True - Description: Controls whether the sensor should be actively sampled. Setting to False stops the data stream.

interval: Duration | None

- Default: None (platform-dependent, typically 200ms. iOS ignores custom intervals.) - Description: Specifies the desired sampling interval using a flet.Duration object.

**Events**

on_error: EventHandler[SensorErrorEvent] | None

- Description: Triggered when the platform reports a sensor error. The event.message attribute contains the error description.

on_reading: EventHandler[BarometerReadingEvent] | None

- Description: Triggered when a new barometer reading is available. The event object contains: - pressure: float (in hPa) - timestamp: int (microseconds since epoch)

**Example Usage**

import flet as ft
def main(page: ft.Page):
    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.append(
        ft.Barometer(
            on_reading=handle_reading,
            on_error=handle_error,
            interval=ft.Duration(milliseconds=500),
        )
    )
    page.add(
        ft.Text("Atmospheric pressure (hPa)."),
        reading := ft.Text("Waiting for data..."),
    )
ft.run(main)