react native gps foreground service - android, kotlin (1)

react native 에서 gps 트래킹을 해야한다. 앱이 백그라운드에 있어도 동작하도록

네이티브 모듈을 만드는 것만 해도 많이 안하다보니 까다로운데 gps + 서비스 동작을 해야한다니.

기본으로 돌아가기로 했다. 일단 안드로이드 앱에서 GPS 트래킹하는 코드부터 시도해보았다.

### MainActivity.kt

```
package com.example.gpstracker

import android.annotation.SuppressLint
import android.content.Context
import android.content.pm.PackageManager
import android.location.LocationListener
import android.location.LocationManager
import android.os.Bundle
import android.util.Log
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.material3.Button
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.Surface
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.core.app.ActivityCompat
import com.example.gpstracker.ui.theme.GpsTrackerTheme

val TAG = "gpstracker"

class MainActivity : ComponentActivity() {
    private lateinit var locationManager: LocationManager
    private lateinit var locationListener: LocationListener

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)


        locationManager = getSystemService(Context.LOCATION_SERVICE) as LocationManager
        locationListener = MyLocationListener()

        if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED &&
            ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this, arrayOf(android.Manifest.permission.ACCESS_FINE_LOCATION), 1)
            Log.d(TAG, "request denied")
            return
        }

        setContent {
            GpsTrackerTheme {
                // A surface container using the 'background' color from the theme
                Surface(
                    modifier = Modifier.fillMaxSize(),
                    color = MaterialTheme.colorScheme.background
                ) {
                    Column {
                        StartButton(locationManager, locationListener)
                        EndButton(locationManager, locationListener)
                    }
                }
            }
        }
    }
}


@SuppressLint("MissingPermission")
@Composable
fun StartButton(locationManager: LocationManager, locationListener: LocationListener) {
    Button(onClick = {
        Log.d(TAG,"start")
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0f, locationListener)
        locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0f, locationListener)
    }) {
        Text(text = "start")
    }
}
@Composable
fun EndButton(locationManager: LocationManager, locationListener: LocationListener) {
    Button(onClick = {
        Log.d(TAG,"end")
        locationManager.removeUpdates(locationListener)
    }) {
        Text(text="end")
    }
}

```

### MyLocationListener
```
package com.example.gpstracker

import android.location.Location
import android.location.LocationListener
import android.util.Log

class MyLocationListener : LocationListener{
    override fun onLocationChanged(p0: Location) {
        val latitude = p0.latitude
        val longitude = p0.longitude
        Log.d(TAG, "Latitude: $latitude, Longitude: $longitude")
    }
}
```
잘 돌아간다. 

펴미션은 아래 두가지를 추가해준다

```
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
```

이제 1초에 한번씩 아무 로그나 찍는 서비스를 구현해본다

```
package com.example.gpstracker

import android.app.NotificationChannel
import android.app.NotificationManager
import android.app.PendingIntent
import android.app.PendingIntent.FLAG_CANCEL_CURRENT
import android.app.Service
import android.content.Intent
import android.os.Build
import android.os.IBinder
import android.util.Log
import androidx.core.app.NotificationCompat
import java.util.Timer
import java.util.TimerTask

class MyForegroundService: Service() {
    private val CHANNEL_ID = "ForegroundServiceChannel"
    private var timer: Timer? = null

    override fun onCreate() {
        super.onCreate()

        Log.d(TAG, "service create")
    }

    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
        Log.d(TAG, "onStartCommand")

        createNotificationChannel()

        val notificationIntent = Intent(this, MainActivity::class.java)

        val pendingIntent = PendingIntent.getActivity(this, 0, notificationIntent,
            PendingIntent.FLAG_IMMUTABLE)

        val notification = NotificationCompat.Builder(this, CHANNEL_ID)
            .setContentTitle("Foreground Service")
            .setContentText("Logging every second")
            .setSmallIcon(R.drawable.ic_launcher_foreground)
            .setContentIntent(pendingIntent)
            .build()

        startForeground(1, notification)

        startLogging()

        return START_STICKY
    }

    override fun onDestroy() {
        super.onDestroy()
        stopLogging()
        Log.d(TAG, "onDestroy")
    }

    override fun onBind(p0: Intent?): IBinder? {
        return null
    }

    private fun createNotificationChannel() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            val serviceChannel = NotificationChannel(
                CHANNEL_ID,
                "Foreground Service Channel",
                NotificationManager.IMPORTANCE_DEFAULT
            )
            val manager = getSystemService(NotificationManager::class.java)
            manager.createNotificationChannel(serviceChannel)
        }
    }

    private fun startLogging() {
        timer = Timer()
        timer?.scheduleAtFixedRate(object : TimerTask() {
            override fun run() {
                Log.d(TAG, "Logging...")
            }
        }, 0, 1000) // Log every 1 second
    }

    private fun stopLogging() {
        timer?.cancel()
    }
}
```

퍼미션과 서비스가 추가되어야 한다
```
<uses-permission android:name="android.permission.FOREGROUND_SERVICE" />

<service
	android:name=".MyForegroundService"
	android:foregroundServiceType="location"
	android:exported="false"/>
```

이제 위의 두가지를 합쳐야 한다.

단순히 `onStartCommand` 에서 `locationManager` 에 위치 요청을 하니 포그라운드 서비스에서 잘 돌았다.

```
@SuppressLint("MissingPermission")
override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
    Log.d(TAG, "onStartCommand")

    createNotificationChannel()

    val notificationIntent = Intent(this, MainActivity::class.java)

    val pendingIntent = PendingIntent.getActivity(this, 0, notificationIntent,
        PendingIntent.FLAG_IMMUTABLE)

    val notification = NotificationCompat.Builder(this, CHANNEL_ID)
        .setContentTitle("Foreground Service")
        .setContentText("Logging every second")
        .setSmallIcon(R.drawable.ic_launcher_foreground)
        .setContentIntent(pendingIntent)
        .build()

    startForeground(1, notification)

    startLogging()

    locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0f, locationListener)
    locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0f, locationListener)

    return START_STICKY
}

override fun onDestroy() {
    super.onDestroy()
    stopLogging()

    locationManager.removeUpdates(locationListener)

    Log.d(TAG, "onDestroy")
}
```

### 전체 코드 github
`https://github.com/qja0707/Kotlin-GPS-ForegroundService`



### what is double colon?
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### What is PendingIntent
서비스 notification channel 을 사용자가 눌렀을 때 작동할 정보. 보통의 안드로이드 앱이라면 액티비티 정보를 넣는 것으로 충분하겠지만...

### What does onStartCommand return integer means? (START_STICKY etc...)
서비스가 어떤식으로 동작해야하는지 명시해주는 Integer이다. 앱이 꺼졌을 때 서비스의 라이프사이클에 관련된 값이라고 생각된다.