Accelerometer EventChannel Utility (Assignment)

Overview This Flutter app reads device accelerometer data from native Android (Kotlin) and iOS (Swift) via an EventChannel and enforces native-side throttling so the Flutter UI only updates 4 times per second (≈250ms). This prevents UI jank while still sampling raw sensor feed at high frequency.

Assignment Requirements Addressed

• Read a high-frequency sensor via EventChannel (Accelerometer).
• Raw data arrives at ≥60 Hz (Android listener uses a fast delay; iOS uses 100 Hz).
• Flutter UI updates limited to 4 Hz (throttled at 250ms on native side).
• Throttling implemented entirely natively (Kotlin/Swift), before sending to Flutter.

Architecture

• Native → EventChannel → Dart Stream → ViewModel → UI widgets.
• Channel name: com.bmoni/accelerometer.
• Payload: { x, y, z, timestamp }.

Native Implementation Android (Kotlin)

• Registers SensorManager listener for TYPE_ACCELEROMETER with SENSOR_DELAY_FASTEST (maximum device-supported rate), captures SensorEvent values.
• Throttles using lastEmitTime and THROTTLE_INTERVAL_MS = 250; only emits when 250ms have elapsed.
• Emits a map to EventChannel; handles no-sensor error; unregisters on cancel.

iOS (Swift)

• Uses CMMotionManager with accelerometerUpdateInterval = 0.01 (100 Hz).
• startAccelerometerUpdates(on main queue) and throttle with lastEmitTime and throttleInterval = 0.25s.
• Emits dictionary with x, y, z and millisecond timestamp; stops updates on cancel.

Dart Layer

• AccelerometerService subscribes to EventChannel broadcast stream, validates payloads, maps to AccelerometerData.
• AccelViewModel collects the last 150 samples and computes magnitude sqrt(x^2 + y^2 + z^2); exposes running/start/stop/clear.
• UI uses Provider selectors to minimize rebuilds and keep frames smooth at throttled cadence.

UI

• NumberCard: latest x, y, z, magnitude + progress bar.
• RadialGauge: circular progress indicator with needle and last magnitude.
• MultilineChart (fl_chart): lines for x, y, z (straight) and magnitude (curved) over the recent window.
• Floating actions: Start/Stop stream, Clear history; tip to move device.

Running

• flutter pub get
• flutter run (attach a physical device).