How to make BroadcastReceiver work even if the app is closed or not running...?

Question

When my app is running or is minimized, it is working fine. but when app is closed it doesn't work.

I want it to work even when it is closed.....please suggest help for this.

SmsReceiver.java

public class SmsReceiver extends BroadcastReceiver{

    String str = "hello";
    MainActivity main = new MainActivity();

    @Override
    public void onReceive(Context context, Intent intent) {
            sendToMain(context,intent);
    }

    public void sendToMain(Context context,Intent intent){

        Toast.makeText(context,"from receiver : "+str, Toast.LENGTH_SHORT).show();            

        Intent i = new Intent(context,MainActivity.class);
        i.putExtra("msg",str);
        i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK| Intent.FLAG_ACTIVITY_CLEAR_TOP|intent.FLAG_ACTIVITY_NO_HISTORY| Intent.FLAG_ACTIVITY_SINGLE_TOP|intent.FLAG_INCLUDE_STOPPED_PACKAGES);
        context.startActivity(i);
    }
}

MainActivity.java

 public class MainActivity extends AppCompatActivity{

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
     }

     @Override
     protected void onNewIntent(Intent intent) {
         Bundle extras = intent.getExtras();
         sms = extras.getString("msg");

         Toast.makeText(MainActivity.this, "from main activity :"+sms, Toast.LENGTH_SHORT).show();
     }
 }

Permissions ->

<uses-permission android:name="android.permission.RECEIVE_SMS"/>
<uses-permission android:name="android.permission.READ_SMS"/>
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>

Receiver -->

    <receiver android:name=".SmsReceiver"
        android:enabled="true"
        android:exported="true">
        <intent-filter>
            <action android:name="android.provider.Telephony.SMS_RECEIVED"/>
            <action android:name="android.intent.action.BOOT_COMPLETED" />
        </intent-filter>
    </receiver>