This sample demonstrates how to parse NMEA sentences and use the results to show device location on the map.
Use case
NMEA sentences can be retrieved from GPS receivers and parsed into a series of coordinates with additional information. Devices without a built-in GPS receiver can retrieve NMEA sentences by using a separate GPS dongle, commonly connected via bluetooth or through a serial port.
The NMEA location data source allows for detailed interrogation of the information coming from the GPS receiver. For example, allowing you to report the number of satellites in view.
How to use the sample
Click floating button "Play" to parse the provided NMEA sentences into a location data source, and display the location position and related satellite information. Click "Stop" to stop displaying the location information. The sample will automatically re-center the location data source as it moves across the map.
How it works
Load NMEA sentences from a local file.
Parse the NMEA sentence strings, and push data into NmeaLocationDataSource.
Set the NmeaLocationDataSource to the LocationDisplay's data source.
Start the location display to begin receiving location and satellite updates.
Relevant API
LocationDisplay
NmeaLocationDataSource
NmeaSatelliteInfo
About the data
This sample reads lines from a local file to simulate the feed of data into the NmeaLocationDataSource. This simulated data source provides NMEA data periodically, and allows the sample to be used on devices without a GPS dongle that produces NMEA data.
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/* Copyright 2022 Esri
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/package com.esri.arcgismaps.sample.displaydevicelocationwithnmeadatasources
import android.os.Bundle
import android.util.Log
import android.view.View
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity
import androidx.appcompat.content.res.AppCompatResources
import androidx.databinding.DataBindingUtil
import androidx.lifecycle.lifecycleScope
import com.arcgismaps.ApiKey
import com.arcgismaps.ArcGISEnvironment
import com.arcgismaps.geometry.Point
import com.arcgismaps.geometry.SpatialReference
import com.arcgismaps.location.LocationDataSourceStatus
import com.arcgismaps.location.LocationDisplayAutoPanMode
import com.arcgismaps.location.NmeaGnssSystem
import com.arcgismaps.location.NmeaLocationDataSource
import com.arcgismaps.mapping.ArcGISMap
import com.arcgismaps.mapping.BasemapStyle
import com.arcgismaps.mapping.Viewpoint
import com.esri.arcgismaps.sample.displaydevicelocationwithnmeadatasources.databinding.ActivityMainBinding
import com.google.android.material.floatingactionbutton.FloatingActionButton
import com.google.android.material.snackbar.Snackbar
import kotlinx.coroutines.launch
import java.io.File
import java.nio.charset.StandardCharsets
import java.util.*
import kotlin.concurrent.timerTask
classMainActivity : AppCompatActivity() {
privateval provisionPath: String by lazy {
getExternalFilesDir(null)?.path.toString() + File.separator + getString(R.string.app_name)
}
// create a new NMEA location data sourceprivateval nmeaLocationDataSource: NmeaLocationDataSource =
NmeaLocationDataSource(SpatialReference.wgs84())
// create a timer to simulate a stream of NMEA dataprivatevar timer = Timer()
// list of nmea location sentencesprivatevar nmeaSentences: List<String>? = emptyList()
// index of nmea location sentenceprivatevar locationIndex = 0// set up data binding for the activityprivateval activityMainBinding: ActivityMainBinding by lazy {
DataBindingUtil.setContentView(this, R.layout.activity_main)
}
privateval mapView by lazy {
activityMainBinding.mapView
}
privateval accuracyTV: TextView by lazy {
activityMainBinding.accuracyTV
}
privateval satelliteCountTV: TextView by lazy {
activityMainBinding.satelliteCountTV
}
privateval satelliteIDsTV: TextView by lazy {
activityMainBinding.satelliteIDsTV
}
privateval systemTypeTV: TextView by lazy {
activityMainBinding.systemTypeTV
}
privateval playPauseFAB: FloatingActionButton by lazy {
activityMainBinding.playPauseFAB
}
overridefunonCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
// authentication with an API key or named user is// required to access basemaps and other location services ArcGISEnvironment.apiKey = ApiKey.create(BuildConfig.API_KEY)
lifecycle.addObserver(mapView)
// create and add a map with a navigation night basemap styleval map = ArcGISMap(BasemapStyle.ArcGISNavigationNight)
mapView.map = map
// set a viewpoint on the map view centered on Redlands, California mapView.setViewpoint(
Viewpoint(
Point(-117.191, 34.0306, SpatialReference.wgs84()), 100000.0 )
)
mapView.locationDisplay.apply {
// set the map view's location display to use the nmea location data source dataSource = nmeaLocationDataSource
// set the map view to recenter on location changed events setAutoPanMode(LocationDisplayAutoPanMode.Recenter)
}
// disable map view interaction, the location display will automatically center on the mock device location mapView.interactionOptions.apply {
isPanEnabled = false isZoomEnabled = false isRotateEnabled = false }
// read nmea location sentences from file nmeaSentences = getNMEASentenceList()
// collects the accuracy for each location change collectLocationChanges()
// collects satellite changes and display satellite information collectSatelliteChanges()
}
/**
* Reads NMEA location sentences from the .nmea file and
* returns it as a [MutableList]
*/privatefungetNMEASentenceList(): List<String>? {
val simulatedNmeaDataFile = File("$provisionPath/Redlands.nmea")
if (!simulatedNmeaDataFile.exists()) {
showError("NMEA file does not exist")
returnnull }
// create list of nmea location sentencesvar nmeaSentences: List<String> = emptyList()
// create a buffered reader using the .nmea fileval bufferedReader = File(simulatedNmeaDataFile.path).bufferedReader()
// read the nmea file contents using a buffered reader and store the mock data sentences in a list bufferedReader.useLines { bufferReaderLines ->
// add carriage return for nmea location data source parser nmeaSentences = bufferReaderLines.map { it + "\n" }.toList()
}
return nmeaSentences
}
/**
* Control the start/stop status of the NMEA location data source
*/funplayPauseClick(view: View) = lifecycleScope.launch {
if (nmeaLocationDataSource.status.value != LocationDataSourceStatus.Started) {
// initialize the location data source and prepare to begin receiving location updates when data is pushed// as updates are received, they will be displayed on the map nmeaLocationDataSource.start().onFailure {
showError("NmeaLocationDataSource failed to start: ${it.message}")
return@launch }
// starts the NMEA mock data sentences nmeaSentences?.let { startNMEAMockData(it) }
setButtonStatus(true)
} else {
// stop receiving and displaying location data nmeaLocationDataSource.stop()
// cancel up the timer task timer.cancel()
setButtonStatus(false)
clearUI()
}
}
/**
* Initializes the location data source, reads the mock data NMEA sentences, and displays location updates from that file
* on the location display. Data is pushed to the data source using a timeline to simulate live updates, as they would
* appear if using real-time data from a GPS dongle
*//**
* Push the mock data NMEA sentences into the data source every 250 ms
*/privatefunstartNMEAMockData(nmeaSentences: List<String>) {
timer = Timer()
timer.schedule(timerTask {
// only push data when startedif (nmeaLocationDataSource.status.value == LocationDataSourceStatus.Started)
nmeaLocationDataSource.pushData(
nmeaSentences[locationIndex++].toByteArray(StandardCharsets.UTF_8)
)
// reset the location index after the last data point is reachedif (locationIndex == nmeaSentences.size) locationIndex = 0 }, 250, 250)
}
/**
* Sets the FAB button to "Start"/"Stop" based on [isShowingLocation]
*/privatefunsetButtonStatus(isShowingLocation: Boolean) = if (isShowingLocation) {
playPauseFAB.setImageDrawable(
AppCompatResources.getDrawable(
this, R.drawable.ic_round_pause_24
)
)
} else {
playPauseFAB.setImageDrawable(
AppCompatResources.getDrawable(
this, R.drawable.ic_round_play_arrow_24
)
)
}
/**
* Collects location changes of the NMEA location data source,
* and displays the location accuracy
*/privatefuncollectLocationChanges() = lifecycleScope.launch {
nmeaLocationDataSource.locationChanged.collect { nmeaLocation ->
// convert from meters to footval horizontalAccuracy = nmeaLocation.horizontalAccuracy * 3.28084val verticalAccuracy = nmeaLocation.verticalAccuracy * 3.28084 accuracyTV.text =
getString(R.string.accuracy) + "Horizontal-%.1fft, Vertical-%.1fft".format(
horizontalAccuracy, verticalAccuracy
)
}
}
/**
* Obtains NMEA satellite information from the NMEA location data source,
* and displays satellite information on the app
*/privatefuncollectSatelliteChanges() = lifecycleScope.launch {
nmeaLocationDataSource.satellitesChanged.collect { nmeaSatelliteInfoList ->
// set the text of the satellite count label satelliteCountTV.text = getString(R.string.satellite_count) + nmeaSatelliteInfoList.size
// get the system of the first satelliteval satelliteSystems = when (nmeaSatelliteInfoList.first().system) {
NmeaGnssSystem.Bds -> "BDS" NmeaGnssSystem.Galileo -> "Galileo" NmeaGnssSystem.Glonass -> "Glonass" NmeaGnssSystem.Gps -> "GPS" NmeaGnssSystem.NavIc -> "NavIc" NmeaGnssSystem.Qzss -> "Qzss" NmeaGnssSystem.Unknown -> "Unknown" }
// get the satellite IDs from the info listval uniqueSatelliteIDs = nmeaSatelliteInfoList.map { it.id }
// display the satellite system and id information systemTypeTV.text = getString(R.string.system) + satelliteSystems
satelliteIDsTV.text = getString(R.string.satellite_ids) + uniqueSatelliteIDs
}
}
/**
* Clears out the info messages when LocationDataSource is paused.
*/privatefunclearUI() {
accuracyTV.text = getString(R.string.accuracy)
satelliteCountTV.text = getString(R.string.satellite_count)
satelliteIDsTV.text = getString(R.string.satellite_ids)
systemTypeTV.text = getString(R.string.system)
}
privatefunshowError(message: String) {
Log.e(localClassName, message)
Snackbar.make(mapView, message, Snackbar.LENGTH_SHORT).show()
}
}