How to Draw Polylines on Google Maps in Android using Jetpack Compose?

Google Maps is used in many Android applications. While using Google Maps there are many modifications that you will get to see while using Maps in this app. When we have used Google Maps in different apps such as OLA and Uber, we will see lines and routes drawn on our Maps. In this article, we will look at drawing Polyline on Google Maps in Android using Jetpack Compose. 

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"?>
<!-- on below line we are creating a container view for our map fragment -->
<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 MainActivity.kt file.

Navigate to app > java > your app’s package name > MainActivity.kt file and add the below code to it. Comments are added in the code to get to know it in detail.

Kotlin

import android.content.Context
import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.fillMaxHeight
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
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.model.LatLng
import com.google.android.libraries.maps.model.PolylineOptions
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
                                    )
                                })
                        }) {
                        mapUI(LocalContext.current)
                        // on below line we are calling method to display UI
                    }
                }
            }
        }
    }
}

@Composable
fun mapUI(context: Context) {
    val mapView = rememberMapViewWithLifecycle()
    // 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
                // on below line we are creating a lat lng variable for all location
                val TamWorth = LatLng(-31.083332, 150.916672)
                val NewCastle = LatLng(-32.916668, 151.750000)
                val Brisbane = LatLng(-27.470125, 153.021072)
                map.addPolyline(
                    PolylineOptions().add(Brisbane, NewCastle, TamWorth, Brisbane)
                        .width // below line is use to specify the width of poly line.
                            (5f) // below line is use to add color to our poly line.
                        .color(context.getColor(R.color.purple_200)) // below line is to make our poly line geodesic.
                        .geodesic(true)
                )
                // on below line we will be starting the drawing of polyline.
                map.moveCamera(CameraUpdateFactory.newLatLngZoom(Brisbane, 13f))
            }
        }
    }
}

Output: