MainActivity.java

Purpose

The MainActivity.java class acts as the Android entry point for the HealthyWear Flutter application. It extends FlutterActivity and bridges native Android functionality with Flutter using MethodChannel and EventChannel. It also manages Bluetooth device scanning and communication for MetaWear and Sensoria sensors.

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Key Imports

import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.content.pm.PackageManager;
import android.Manifest;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.le.ScanResult;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.NotificationChannel;
import android.os.Build;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;
import androidx.annotation.NonNull;

Flutter & Plugin APIs

import io.flutter.embedding.android.FlutterActivity;
import io.flutter.embedding.engine.FlutterEngine;
import io.flutter.plugin.common.MethodChannel;
import io.flutter.plugin.common.EventChannel;

Networking

import okhttp3.*;

MetaWear SDK

import com.mbientlab.metawear.android.BtleService;

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Responsibilities

• Bluetooth Permission Handling

• MetaWear Service Binding

• File Upload via OkHttp

• Event Channels for MetaWear and Sensoria status streaming

• Flutter MethodChannel Handlers for platform interop

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Flutter Channels

MethodChannels

Handles one-shot requests from Flutter, such as:

• Uploading files to server

• Initiating sensor commands

• Querying permission status

EventChannels

Enables real-time stream communication to Flutter, such as:

• metawear_connection_status

• sensoria_connection_status

These push live BLE connection updates into the Dart application UI layer.

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Service Binding

Intent serviceIntent = new Intent(this, BtleService.class);
bindService(serviceIntent, serviceConnection, Context.BIND_AUTO_CREATE);

Binds the Android service used to communicate with MetaWear sensors.

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Notifications

NotificationCompat.Builder builder = new NotificationCompat.Builder(this, CHANNEL_ID)

Custom notifications are created during scanning or error handling.

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Uploads

RequestBody fileBody = RequestBody.create(file, MediaType.parse("application/octet-stream"));
Request request = new Request.Builder().url(serverUrl).post(requestBody).build();

Files are uploaded from Android storage using OkHttp.

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Structure

• configureFlutterEngine() sets up all channels and service bindings.

• Sensors are initialized via SensorHandler objects.

• Communication is managed using EventSink.

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Platform-Specific Logic

All Bluetooth and file-handling operations are done through native Android code, while status and results are forwarded to Flutter through interop channels.