How to pass Location type ArrayList to MapsActivity from MainActivity in android?

Question

What I'm trying to do is pass a list of locations to maps activity and put marker on those locations. I've tried using in MainActivity

public class MainActivity extends AppCompatActivity implements Parcelable {

ArrayList<Location> locs=new ArrayList<>();
...
locs.add(location);
...
Intent in = new Intent(context,MapsActivity.class);
in.putExtra("setlocations",locs);
startActivity(in);
...
 @Override
public int describeContents() {
    return 0;
}

@Override
public void writeToParcel(Parcel dest, int flags) {
    dest.writeList(locs);

}
}

And then in MapsActivity's onCreate()

 Bundle extras = getIntent().getExtras();
    if(extras != null){
        locs=(ArrayList<Location>)getIntent().getParcelableExtra("setlocations");
        addMarkeratLocation();
    }

The addMarkeratLocation() method uses locs list for adding markers using for loop

public void addMarkeratLocation(){
    BitmapDescriptor icon = BitmapDescriptorFactory.fromResource(R.mipmap.dott);
    LatLng addpoint=new LatLng(0.0,0.0);
    for(int i=0;i<locs.size();i++){
        addpoint = new LatLng(locs.get(i).getLatitude(), locs.get(i).getLongitude());
        mMap.addMarker(new MarkerOptions().position(addpoint).icon(icon));
     }
    mMap.moveCamera(CameraUpdateFactory.newLatLng(addpoint));
}

My application crashes when the intent is fired. And the logcat shows java.lang.NullPointerException: Attempt to invoke virtual method 'int java.util.ArrayList.size()' on a null object reference Why it is showing null? This is first time I'm using Parcelable interface.. Is there anything that I'm missing? Any input will be appreciated, thanks.

Nandhakumar Appusamy · Accepted Answer · 2017-09-11 15:55:09Z

5

`Location` class is not a Parcalable class.

Intent.putExtra() function only accept primitive and Parcelable data type. So you can not pass List<Location> through intent. Instead you can use Gson library to serialise you arraylist of Location and pass it as Json string to MapActivity and In MapActivity deserialise Json string to array of Location.

edited Sep 11, 2017 at 15:55

answered Sep 10, 2017 at 20:20

Nandhakumar Appusamy

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2 Comments

Diksha Over a year ago

can you provide any example of that..?

Nandhakumar Appusamy Over a year ago

Sure I'll put details answer

Nandhakumar Appusamy · Accepted Answer · 2017-09-11 17:02:24Z

4

Step 1: First Import Gson Library using Gradle Script

Add this line in your Gradle dependency

dependencies {
    compile 'com.google.code.gson:gson:2.7'
}

Step 2: Convert List into JSON String and pass the JSON String from MainActivity to MapsActivity

        Location location1 = new Location("");
        location1.setLatitude(12.124);
        location1.setLongitude(77.124);
        Location location2 = new Location("");
        location2.setLatitude(12.765);
        location2.setLatitude(77.8965);

        List<Location> locations = new ArrayList<Location>();
        locations.add(location1);
        locations.add(location2);

        Gson gson = new Gson();
        String jsonString = gson.toJson(locations);
        Intent intent = new Intent(MainActivity.this,MapsActivity.class);
        intent.putExtra("KEY_LOCATIONS",jsonString);
        startActivity(intent);

Step 3: Get the JSON String from Bundle and convert it to List

        Bundle bundle = getIntent().getExtras();
        String jsonString = bundle.getString("KEY_LOCATIONS");

        Gson gson = new Gson();
        Type listOfLocationType = new TypeToken<List<Location>>() {}.getType();
        List<Location> locations = gson.fromJson(jsonString,listOfLocationType );

I hope this might help you!!

answered Sep 11, 2017 at 17:02

Nandhakumar Appusamy

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7 Comments

Diksha Over a year ago

There are multiple import options for Type package.. which one shall I import?

Nandhakumar Appusamy Over a year ago

import java.lang.reflect.Type;

Diksha Over a year ago

App crashes giving error

java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.android.gms.maps.model.Marker com.google.android.gms.maps.GoogleMap.addMarker(com.google.android.gms.maps.model.MarkerOptions)' on a null object reference

on the line of adding marker, this is how I'm adding marker

mMap.addMarker(new MarkerOptions().position(addpoint).icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_ORANGE)));

Nandhakumar Appusamy Over a year ago

The variables location1 and location2 are incomplete that may be the issue but I'm not sure. Try to pass complete location variable. But above method will sure let you pass List<Location> to other Activity

Diksha Over a year ago

I'm adding locations to the list in onLocationChanged method

|

Chandresh Tarasariya · Accepted Answer · 2017-09-11 10:19:15Z

0

ArrayList locs=new ArrayList<>(); Location class should be implemented with Parcelable, you already implemented Parcelable but it is for activity that should be for Location class.

Please refer below link for more info related your query.

Passing arraylist of custom object to another activity

answered Sep 11, 2017 at 10:19

Chandresh Tarasariya

492 bronze badges

2 Comments

Diksha Over a year ago

That Location class is the android's inbuilt class... how can I implement that with Parcelable??

Chandresh Tarasariya Over a year ago

you need to create your own class and that class should have that location class example:- create another class MyLocationClass so array will be ArrayList<MyLocationClass> and MyLocationClass should have implemented with Parcelable.

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