How to Draw Polyline in Google Maps in Android?

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

What we are going to build in this article? 

We will be building a simple application in which we will display our Map. On this map, we will display a polygon between three locations as Brisbane, Tamworth, and Newcastle. A sample image is given below to get an idea about what we are going to do in this article. Note that we are going to implement this project using the Java language. 

Step by Step Implementation

Step 1: Create a New Project

To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. Note that select Java as the programming language. Make sure to select Maps Activity while creating a new Project.

Step 2: Generating an API key for using Google Maps

To generate the API key for Maps you may refer to How to Generate API Key for Using Google Maps in Android. After generating your API key for Google Maps. We have to add this key to our Project. For adding this key in our app navigate to the values folder > google_maps_api.xml file and at line 23 you have to add your API key in the place of YOUR_API_KEY. 

Step 3: Adding Polyline on Google Maps in Android

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

Java

import android.graphics.Color;
import android.os.Bundle;

import androidx.fragment.app.FragmentActivity;

import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.PolylineOptions;

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {

    private GoogleMap mMap;

    // below are the latitude and longitude of 4 different locations.
    LatLng TamWorth = new LatLng(-31.083332, 150.916672);
    LatLng NewCastle = new LatLng(-32.916668, 151.750000);
    LatLng Brisbane = new LatLng(-27.470125, 153.021072);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);
        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
    }

    /**
     * Manipulates the map once available.
     * This callback is triggered when the map is ready to be used.
     * This is where we can add markers or lines, add listeners or move the camera. In this case,
     * we just add a marker near Sydney, Australia.
     * If Google Play services is not installed on the device, the user will be prompted to install
     * it inside the SupportMapFragment. This method will only be triggered once the user has
     * installed Google Play services and returned to the app.
     */
    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
        // inside on map ready method
        // we will be displaying polygon on Google Maps.
        // on below line we will be adding polyline on Google Maps.
        mMap.addPolyline((new PolylineOptions()).add(Brisbane, NewCastle, TamWorth, Brisbane).
                        // below line is use to specify the width of poly line.
                        width(5)
                        // below line is use to add color to our poly line.
                        .color(Color.RED)
                        // below line is to make our poly line geodesic.
                        .geodesic(true));
        // on below line we will be starting the drawing of polyline.
        googleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(Brisbane, 13));
    }
}

After adding this code. Now run your app and see the output of the app.

Output:

Note: In the Google Developer Console (https://console.developers.google.com), ensure that the “Google Maps Android API v2” is enabled. And also ensure that your API Key exists.