CODEWITHSUNDEEP
javaandroidgoogle-maps
JDoe
JDoe

Reputation: 221

Android - Displaying Polyline

The concept of my application is that a a path is drawn every time a user sets two markers on a map and that path is shown in another activity. I have saved the path (waypoints) as an Array list in my FireBase database and I have also retrieved the way points in the second activity, but I am having problems displaying the poly line in the second activity. My database:

enter image description here

My POJO classes:

public static class Route {

    private ArrayList<Location> locations;

    public Route() {
    }

    @PropertyName("route")
    public ArrayList<Location> getLocations() {
        return locations;
    }

    @PropertyName("route")
    public void setLocations(ArrayList<Location> locations) {
        this.locations = locations;
    }
}


public static class Location {
    private Double latitude;
    private Double longitude;

    public Location() {
    }

    public Double getLatitude() {
        return latitude;
    }

    public void setLatitude(Double latitude) {
        this.latitude = latitude;
    }

    public Double getLongitude() {
        return longitude;
    }

    public void setLongitude(Double longitude) {
        this.longitude = longitude;
    }
}

Retrieval of waypoints:

 userRef.child("Route").addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            Route route = dataSnapshot.getValue(Route.class);
            for (Location location : route.getLocations()) {
                points = new ArrayList();
                double lat = location.getLatitude();
                double lng = location.getLongitude();
                position = new LatLng(lat, lng);
                points.add(position);
            }
        }

To add the polyline to the map I do this:

 PolylineOptions lineOptions = null;
    lineOptions.add(position);
    lineOptions.width(12);
    lineOptions.color(Color.RED);

    mMap.addPolyline(lineOptions);

But I get this exception :

"NullPointerException: Attempt to invoke virtual method 'com.google.android.gms.maps.model.PolylineOptions com.google.android.gms.maps.model.PolylineOptions.add(com.google.android.gms.maps.model.LatLng)' on a null object reference"

Upvotes: 2

Views: 850

Answers (1)

Nabin Bhandari
Nabin Bhandari

Reputation: 16379

What about writing 

PolylineOptions lineOptions = new PolylineOptions();

instead of

PolylineOptions lineOptions = null;

Also you are adding a single point in the polyline. Loop through your list points and add all of them.

for (LatLng point: points){
    lineOptions.add(point);
}
mMap.addPolyline(lineOptions);

Your another mistake:

You are recreating the ArrayList as points = new ArrayList(); inside for loop. Use it before for loop.

points = new ArrayList();
for (Location location : route.getLocations()) {
    //your code
}

Upvotes: 3

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