Android Jetpack Compose – Calculate Distance Between Two Locations

We have seen many apps that use Google Maps. These maps are used to indicate places on Google Maps and also we can use this to calculate the distance between two locations. In this article, we will take a look at calculating the distance between two locations in Android. A sample video is given below to get an idea about what we are going to do in this article.

Step by Step Implementation

Step 1: Create a New Project in Android Studio

To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. While choosing the template, select Empty Compose Activity. If you do not find this template, try upgrading the Android Studio to the latest version. We demonstrated the application in Kotlin, so make sure you select Kotlin as the primary language while creating a New Project.

Step 2: Adding a new color to the Color.kt file

Navigate to app > java > your app’s package name > ui.theme > Color.kt file and add the below code to it. 

Kotlin

import androidx.compose.ui.graphics.Color

val Purple200 = Color(0xFF0F9D58)
val Purple500 = Color(0xFF0F9D58)
val Purple700 = Color(0xFF3700B3)
val Teal200 = Color(0xFF03DAC5)

// on below line we are adding different colors.
val greenColor = Color(0xFF0F9D58)

Step 3: Adding Dependency to use Google Maps

Navigate to build.gradle file and add the below dependency in the build.gradle file.

implementation("com.google.android.libraries.maps:maps:3.1.0-beta")
implementation("com.google.maps.android:maps-v3-ktx:2.2.0")
implementation("androidx.fragment:fragment:1.3.2")

After adding the dependency simply click on the sync now option to install it.

Step 4: Adding Permissions and Google Maps API key

Navigate to app > AndroidManifest.xml file and add the below code in the application tag for adding the API key.

<meta-data
android:name="com.google.android.geo.API_KEY"
android:value="Enter your API key" />

Check out the below article on How to Generate API Key for Using Google Maps in Android?

Step 5: Create a New Layout File for Map Layout

Navigate to app > res > Right click on it > New > Directory and name it as layout. Now right-click on that directory and click on New > Layout resource file. Create a new xml file and name it map_layout and add the below code to it. Comments are added in the code to get to know it in detail. 

XML

<?xml version="1.0" encoding="utf-8"?>
<androidx.fragment.app.FragmentContainerView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/map"
    android:name="com.google.android.gms.maps.SupportMapFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

Step 6: Create a new file for creating a Map

Navigate to app>java>your app’s package name>Right click on it>New>Kotlin class and name it as MapUtils and add the below code to it. Comments are added in the code to get to know it in detail.

Kotlin

import android.os.Bundle
import androidx.compose.runtime.Composable
import androidx.compose.runtime.DisposableEffect
import androidx.compose.runtime.remember
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.platform.LocalLifecycleOwner
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.LifecycleEventObserver
import com.google.android.libraries.maps.MapView

// on below line creating a new
// composable widget for displaying map
@Composable
fun rememberMapViewWithLifecycle(): MapView {
    val context = LocalContext.current
    // on below line initializing
    // our maps view with id.
    val mapView = remember {
        MapView(context).apply {
            id = R.id.map
        }
    }

    // Makes MapView follow the lifecycle of this composable
    val lifecycleObserver = rememberMapLifecycleObserver(mapView)
    // on below line initializing lifecycle variable.
    val lifecycle = LocalLifecycleOwner.current.lifecycle
    // on below line adding observer for lifecycle.
    DisposableEffect(lifecycle) {
        lifecycle.addObserver(lifecycleObserver)
        onDispose {
            lifecycle.removeObserver(lifecycleObserver)
        }
    }
    // returning map view on below line.
    return mapView
}

@Composable
// creating a function for map lifecycle observer.
fun rememberMapLifecycleObserver(mapView: MapView): LifecycleEventObserver =
    remember(mapView) {
        // on below line adding different events for maps view
        LifecycleEventObserver { _, event ->
            when (event) {
                Lifecycle.Event.ON_CREATE -> mapView.onCreate(Bundle())
                Lifecycle.Event.ON_START -> mapView.onStart()
                Lifecycle.Event.ON_RESUME -> mapView.onResume()
                Lifecycle.Event.ON_PAUSE -> mapView.onPause()
                Lifecycle.Event.ON_STOP -> mapView.onStop()
                Lifecycle.Event.ON_DESTROY -> mapView.onDestroy()
                else -> throw IllegalStateException()
            }
        }
    }

Step 7: Working with the MainActivity.kt file

Go to the MainActivity.kt file and refer to the following code. Below is the code for the MainActivity.kt file. Comments are added inside the code to understand the code in more detail.

Kotlin

package com.example.newcanaryproject

import android.content.Context
import android.location.Location
import android.os.Bundle
import android.util.Log
import android.widget.Toast
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.*
import androidx.compose.material.*
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.text.style.TextAlign
import androidx.compose.ui.viewinterop.AndroidView
import com.example.newcanaryproject.ui.theme.NewCanaryProjectTheme
import com.example.newcanaryproject.ui.theme.greenColor
import com.google.android.libraries.maps.CameraUpdateFactory
import com.google.android.libraries.maps.MapView
import com.google.android.libraries.maps.model.LatLng
import com.google.android.libraries.maps.model.MarkerOptions
import com.google.maps.android.ktx.awaitMap
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.launch

class MainActivity : ComponentActivity() {

    var message = ""
    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)
        setContent {
            NewCanaryProjectTheme {
                // on below line we are specifying
                // background color for our application
                Surface(
                    // on below line we are specifying modifier and color for our app
                    modifier = Modifier.fillMaxSize(), color = MaterialTheme.colors.background
                ) {
                    // on the below line we are specifying
                    // the theme as the scaffold.
                    Scaffold(
                        // in scaffold we are
                        // specifying the top bar.
                        topBar = {
                            // inside top bar we are specifying
                            // background color.
                            TopAppBar(backgroundColor = greenColor,
                                // along with that we are specifying
                                // title for our top bar.
                                title = {
                                    // in the top bar we are
                                    // specifying tile as a text
                                    Text(
                                        // on below line we are specifying
                                        // text to display in top app bar
                                        text = "GFG",
                                        // on below line we are specifying
                                        // modifier to fill max width
                                        modifier = Modifier.fillMaxWidth(),
                                        // on below line we are
                                        // specifying text alignment
                                        textAlign = TextAlign.Center,
                                        // on below line we are
                                        // specifying color for our text.
                                        color = Color.White
                                    )
                                })
                        }) {
                        // on below line we are calling
                        // method to display UI
                        mapUI(LocalContext.current)
                    }
                }
            }
        }
    }
}

@Composable
fun mapUI(context: Context) {
    val mapView = rememberMapViewWithLifecycle()
    // on below line creating a variable for location.
    // on below line creating a column for our maps.
    Column(
        modifier = Modifier
            .fillMaxHeight()
            .fillMaxWidth()
            .background(Color.White)
    ) {
        // on below line adding a map view to it.
        AndroidView({ mapView }) { mapView ->
            // on below line launching our map view
            CoroutineScope(Dispatchers.Main).launch {
                val map = mapView.awaitMap()
                // on below line adding zoom controls for map.
                map.uiSettings.isZoomControlsEnabled = true
                getDistance(mapView, context)
            }
        }
    }
}

private fun getDistance(mapView: MapView, context: Context) {
    // on below line we are getting our map view.
    mapView.getMapAsync {
        // on below line adding co ordinates.
        val Sydney = LatLng(-34.0, 151.0)
        val Brisbane = LatLng(-27.470125, 153.021072)
        // on below line creating variable for
        // location a and location b.
        // on below line setting lat and lng.
        val locationA: Location = Location("Sydney")
        locationA.latitude = Sydney.latitude
        locationA.longitude = Sydney.longitude
        val locationB: Location = Location("Brisbane")
        locationB.latitude = Brisbane.latitude
        locationB.longitude = Brisbane.longitude

        // on below line calculating distance.
        var distance: Float = locationA.distanceTo(locationB)
        distance /= 1000

        // on below line displaying toast message.
        Toast.makeText(
            context,
            "Distance between Sydney and Brisbane is : " + distance + "km",
            Toast.LENGTH_SHORT
        )
            .show()

        // creating array list for adding all our locations.
        // in below line we are initializing our array list.
        val locationArrayList: ArrayList<LatLng?> = ArrayList()
        // on below line we are adding
        // our locations in our array list.
        locationArrayList.add(Sydney)
        locationArrayList.add(Brisbane)
        // inside that we are drawing marker on our map.
        for (i in locationArrayList.indices) {
            // below line is use to add marker to each location of our array list.
            it.addMarker(MarkerOptions().position(locationArrayList[i]!!).title("Marker"))
            // below line is use to zoom our camera on map.
            it.animateCamera(CameraUpdateFactory.zoomTo(18.0f))
            // below line is use to move our camera to the specific location.
            it.moveCamera(CameraUpdateFactory.newLatLng(locationArrayList[i]))
        }
    }
}

Now run your application to see the output of it. 

Output: