Firebase 如何动态更新谷歌地图上的标记位置？

我正在创建一个约会应用程序，它将使用谷歌地图，以显示一定范围内的所有用户，并跟踪他们的移动。我已经从Firebase数据库中检索了数据，并将其以标记的形式显示在地图上，但我真的不知道如何实现位置的自动更新。现在可以通过手动刷新地图来查看更改

这是我的onCreate函数：

override fun onCreate(savedInstanceState: Bundle?) 
       super.onCreate(savedInstanceState)
       setContentView(R.layout.activity_maps)

       mFusedLocationProviderClient = LocationServices.getFusedLocationProviderClient(this)
       mapFrag = supportFragmentManager.findFragmentById(R.id.map) as SupportMapFragment
       mapFrag?.getMapAsync(this)

override fun onMapReady(googleMap: GoogleMap?) {
        map = googleMap!!
        map.mapType = GoogleMap.MAP_TYPE_NORMAL
        mLocationRequest = LocationRequest()
        mLocationRequest.interval = 120000
        mLocationRequest.fastestInterval = 120000
        mLocationRequest.priority = LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY
        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M){
            if(ContextCompat.checkSelfPermission(this,android.Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED)
            {
                mFusedLocationProviderClient?.requestLocationUpdates(mLocationRequest,mLocationCallback, Looper.myLooper()!!)
                map.isMyLocationEnabled = true
                update_pr()
            }
            else
            {
                checkLocationPermission()
            }
        }
        else
        {
            mFusedLocationProviderClient?.requestLocationUpdates(mLocationRequest,mLocationCallback,Looper.myLooper()!!)
        }

和onMapReady函数：

override fun onCreate(savedInstanceState: Bundle?) 
       super.onCreate(savedInstanceState)
       setContentView(R.layout.activity_maps)

       mFusedLocationProviderClient = LocationServices.getFusedLocationProviderClient(this)
       mapFrag = supportFragmentManager.findFragmentById(R.id.map) as SupportMapFragment
       mapFrag?.getMapAsync(this)

override fun onMapReady(googleMap: GoogleMap?) {
        map = googleMap!!
        map.mapType = GoogleMap.MAP_TYPE_NORMAL
        mLocationRequest = LocationRequest()
        mLocationRequest.interval = 120000
        mLocationRequest.fastestInterval = 120000
        mLocationRequest.priority = LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY
        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M){
            if(ContextCompat.checkSelfPermission(this,android.Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED)
            {
                mFusedLocationProviderClient?.requestLocationUpdates(mLocationRequest,mLocationCallback, Looper.myLooper()!!)
                map.isMyLocationEnabled = true
                update_pr()
            }
            else
            {
                checkLocationPermission()
            }
        }
        else
        {
            mFusedLocationProviderClient?.requestLocationUpdates(mLocationRequest,mLocationCallback,Looper.myLooper()!!)
        }