import com.google.android.gms.tasks.Task; import com.google.android.gms.tasks.OnCompleteListener; import com.google.android.gms.tasks.TaskCompletionSource; import com.google.android.gms.tasks.Tasks; Task<String> task = TaskCompletionSource<String>(); task.addOnCompleteListener(new OnCompleteListener<String>() { @Override public void onComplete(Task<String> task) { if (task.isSuccessful()) { String result = task.getResult(); } else { Exception exception = task.getException(); } } }); Tasks.call(someBackgroundExecutor, new Callable<String>() { @Override public String call() throws Exception { return someAsyncOperation(); } });