Start a new activity when app is fresh started and minimized

First time asking a question, please be polite :)

I want to create an app that when you get an incoming call shows you a message(by starting a new Activity).

I did it, except for one problem. When I first start the app:

1)I have to make a phone call while the app is running upfront in order to work as planned.

2)Then I can minimize it

3)Or even lock the phone and the app is running perfectly

BUT

1)If i start the app

2)Minimize it

3)And then make the phone call nothing happens :(

4)I have to open it , make the phone call and then minimize again to run as it should be.

I am using the android emulator to test it .

MainActivity:

public class MainActivity extends AppCompatActivity
{


    IntentFilter intentFilter;
    CallReceiver callReceiver;


    private void init()
    {
        intentFilter = new IntentFilter();
        callReceiver = new CallReceiver();
    }


    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        init();



        intentFilter.addAction("android.intent.action.PHONE_STATE");
        intentFilter.addAction("android.intent.action.NEW_OUTGOING_CALL");

        registerReceiver(callReceiver,intentFilter);


    }

CallReceiver:

public class CallReceiver extends PhonecallReceiver
    {

        public static final String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";


        @Override
        protected void onIncomingCallStarted(Context ctx, String number, Date start)
        {

            openNewActivity(number,ctx);

        }

        @Override
        protected void onOutgoingCallStarted(Context ctx, String number, Date start)
        {
        }

        @Override
        protected void onIncomingCallEnded(Context ctx, String number, Date start, Date end)
        {
        }

        @Override
        protected void onOutgoingCallEnded(Context ctx, String number, Date start, Date end)
        {
        }

        @Override
        protected void onMissedCall(Context ctx, String number, Date missed)
        {
        }



        private void openNewActivity(String number,Context context)
        {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    final StringBuilder builder = new StringBuilder();

                    try {
                        
                        Intent i = new Intent(context, IncomingCallActivity.class);
                        String message = "Message I want to be displayed";
                        i.putExtra(EXTRA_MESSAGE, message);


                        final Handler handler = new Handler(Looper.getMainLooper());
                        handler.postDelayed(new Runnable() {
                            @Override
                            public void run() {
                                //Do something after 100ms
                                context.startActivity(i);
                            }
                        }, 1000);


                    } catch (Exception e) {
                        builder.append("Error : ").append(e.getMessage()).append("\n");
                    }

                }
            }).start();
        }
    }

IncomingCallActivity:

public class IncomingCallActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        // Important: have to do the following in order to show without unlocking
        this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN |
                        WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED |
                        WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON,
                WindowManager.LayoutParams.FLAG_FULLSCREEN |
                        WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED |
                        WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON);

        setContentView(R.layout.main);

        Intent intent = getIntent();
        String message= intent.getStringExtra(CallReceiver.EXTRA_MESSAGE);

        TextView text = (TextView)findViewById(R.id.text);
        text.setText(message);
    }
}