How to Add an Android Header in a Calling App

This tutorial demonstrates how to make a Sinch app-to-app call with a header. In this app, I’ll send the location of the person calling so the recipient can see where the other user is calling from. finished-app.png

The app is built on top of the sinch-rtc-sample-calling sample included in the Android SDK, and the finished code can be found on our GitHub.


  1. Create a free Sinch developer account
  2. Create an app in the Developer Dashboard
  3. Download the Sinch Android SDK
  4. Add your app key and secret to the sinch-rtc-sample-calling app included in the SDK (in

Update SinchServiceInterface

Sinch allows you to make an app-to-app call and send along a Map<String, String> of headers. First, extend the SinchServiceInterface in to support this method:

public Call callUser(String userId, Map<String, String> headers) {
    return mSinchClient.getCallClient().callUser(userId, headers);

Get location and make the call

You’ll need the following permission to access the device’s location:

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>

Now, in callButtonClicked in, you can get the latitude and longitude of the last known location:

LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
Location lastLoc = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
Double longitude = lastLoc.getLongitude();
Double latitude = lastLoc.getLatitude();


This is definitely not a production-ready way of getting an accurate location. First of all, your app will crash if the user doesn’t have any “last location.” You could also use the ACCESS_COARSE_LOCATION permission, since you don’t need to know their exact location. Regardless, there are several location strategies and I suggest doing some research if you want to send a current location in your production app.

Use a Geocoder object to turn the latitude and and longitude into a human-readable address:

Geocoder geocoder = new Geocoder(this, Locale.getDefault());
List<Address> addresses = null;
try {
    addresses = geocoder.getFromLocation(latitude, longitude, 1);
} catch (IOException e) {

I chose to send the city/state/zipcode of the location as the header:

Map<String, String> headers = new HashMap<String, String>();
headers.put("location", addresses.get(0).getAddressLine(0));

You can add as many items as you like to the headers like so:

headers.put("key", "value");

Finally, change this line that makes the call:

Call call = getSinchServiceInterface().callUser(userName);

to this:

Call call = getSinchServiceInterface().callUser(userName, headers);

Display header value on incoming call

In SinchCallClientListener#onIncomingCall in, get the location value from the headers, and pass it along in the intent:

intent.putExtra("location", call.getHeaders().get("location"));

Then, in, you can get the location from the intent like so:

String location = getIntent().getStringExtra(SinchService.LOCATION);

I chose to create a TextView with ID remoteUserLocation in incoming.xml, so I could set it to the location from the header in onServiceConnected (right where the remoteUserId TextView is set).

TextView remoteUserLocation = (TextView) findViewById(;
remoteUserLocation.setText("Calling from " + mCallLocation);

That’s all! Rinse and repeat for any data you want to send along with an app-to-app call.