.

app/src/main/java/com/example/mysmsapp/MainActivity.java

@@ -6,6 +6,7 @@ import android.content.Intent;
 import android.os.Build;
 import android.os.Bundle;
 import android.provider.Settings;
+import android.telephony.SmsManager;
 import android.telephony.SubscriptionInfo;
 import android.telephony.SubscriptionManager;
 import android.telephony.TelephonyManager;
@@ -78,6 +79,7 @@ public class MainActivity extends AppCompatActivity {
             Log.i(TAG, "NetworkCountryIso: " + telephonyManager.getNetworkCountryIso());
             Log.i(TAG, "subId: " + telephonyManager.getSubscriptionId());
             Log.i(TAG, "subscriberId: " + telephonyManager.getSubscriberId());
+            Log.i(TAG, "getDefaultSubId: " + SmsManager.getSmsManagerForSubscriptionId(1).getSubscriptionId());
             SubscriptionManager subscriptionManager = SubscriptionManager.from(this);
             final int simCount = subscriptionManager.getActiveSubscriptionInfoCountMax();