How to pass data from BroadcastReceiver to Activity without in onCreate()

I have a serious issue about passing data from BroadcastReceiver to an Activity. Let see my issue carefully. I have a class PhoneStateReceiver extends BroadcastReceiver that used to received an incoming phone.

public class PhoneStateReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        try {
            System.out.println("Receiver start");
            String state = intent.getStringExtra(TelephonyManager.EXTRA_STATE);
            String incomingNumber = intent.getStringExtra(TelephonyManager.EXTRA_INCOMING_NUMBER);
            if(state.equals(TelephonyManager.EXTRA_STATE_RINGING)){

            }            
        }
        catch (Exception e){
            e.printStackTrace();
        }
    }
}

The incoming phone will be sent to an Activity, called ReceiverActivity. The ReceiverActivity receives the incoming phone and sends it to a server via a socket connection. The socket connection is initialized in the onCreate function. I googled and found server way to pass the data from BroadcastReceiver to an Activity. The common way is that send data via putExtra function and call startActivity. However, the way will call the onCreate again and then connect the socket, draw the UI again. Thus, it is not helpful in my case.

In my goal, If the phone receives an incoming call, it will send the incoming call to the ReceiverActivity. The ReceiverActivity receives the message and calls the send function. Which is the best way to do it? Thank you

The common way to pass data from a BroadcastReceiver to a ReceiverActivity that I used as follows

In PhoneStateReceiver class :

Intent intent_phonenum = new Intent(context, ReceiverActivity.class);
intent_phonenum.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent_phonenum.putExtra("phone_num", incomingNumber);
context.startActivity(intent_phonenum);

In ReceiverActivity class :

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        connect_socket();
        Intent intent = getIntent();
        phone_num = intent.getStringExtra("phone_num");
        send(phone_num);
}

There is a very simple design pattern you can use here to ease communication between your classes and also decouple your code: publisher/subscriber. My favorite library for this is EventBus:

First, add to your build.gradle file:

compile 'org.greenrobot:eventbus:3.0.0'

Then, create a simple POJO - Plain Old Java Object like this:

public class OnReceiverEvent{
   private String phoneNumber;

   public OnReceiverEvent(String phone){
      this.phoneNumber = phone;
   }

   public String getPhoneNumber(){
      return phoneNumber;
   }
}

Next, by making your Receiver class a publisher, and your Activity a subscriber, you should be able to easily pass the information to your activity like this:

//inside your PhoneStateReceiver class when you want to pass info

EventBus.getDefault().post(new OnReceiverEvent(phoneNumber));

Next, inside your activity, simply do this:

//onStart
@Override
public void onStart(){
   super.onStart();
   EventBus.getDefault().register(this);
}

//onStop
@Override
public void onStop(){
   super.onStop();

   EventBus.getDefault().unregister(this);
}

Finally, handle the posted data i.e phoneNumber value:

@Subscribe
public void onPhoneNumberReceived(OnReceiverEvent event){
   //get the phone number value here and do something with it

   String phoneNumber = event.getPhoneNumber();

   //display or something?
}

UPDATE

If you have another Event that you want this activity to subscribe to, simply create a method like you did in the first one using the @Subscribe annotation.

@Subscribe
public void onSomeOtherEvent(EventClassName event){
   //get the variables here as usual;
}

This is the easiest way to pass the data from your receiver to your activity without having to worry about starting the activity over and over!

I hope this helps and good luck!