How to Receive and Handle SMS on Android Applications

Android Despite the popularity of social media networks and messengers, texting is still the most common way to communicate via smartphones. According to the 2020 State of Texting report by Zipwhip, 77% of people use their texting app more frequently than other messengers.

Android

But default SMS applications aren’t always comfortable for users, who start looking for third-party apps. Additionally, non-messenger Android applications may still need SMS handling functionality (for example to confirm SMS authentication codes). In this article, we share our experience in developing SMS (and other service) handlers. In particular, we describe how to:

  • Make your application the default SMS handler
  • Develop an SMS receiver
  • Encrypt and decrypt SMS messages
  • Add texts to the SMS table in a device database

This text will be useful for developers who need to add SMS handling functionality to their app or create a new SMS messaging app.

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Making an app the default SMS handler

It’s important to make your application the default for handling SMS messages because only such app can record data to the SMS database. Your app should request permission to become the default SMS app before requesting any other permissions. This is also a requirement of the Google Play Store: if an app requests SMS, MMS, or CALL LOG permissions and isn’t a default SMS or Contact app, it will be rejected by Google.

Developing the Android app manifest file

The app manifest file is a very important part of an Android application. It contains information on the app’s:

  • Package name
  • Components (activities, content providers, services, broadcast receivers)
  • Required permissions
  • Required software and hardware features

Let’s focus on the permissions for our application.

In Android 6, Google introduced runtime permissions. They protect the privacy of user data, tell users what information will be used by the app, and make sure users understand what an app can do with their data.

Encrypting and decrypting SMS messages

All texts that our app receives will be encrypted. To handle them, we need to add a class that provides encryption and decryption.

In our application, encryption is done by executing the fun encrypt(data: String): String function. It encrypts a string with a key generated using the Password-Based Key Derivation Function (PBKDF2) algorithm. The returned value is an encrypted Base64 string.

Handling received SMS messages

The main class that receives SMS messages is SmsReceiver. It extends the BroadcastReceiver class. Any child class of BroadcastReceiver must contain the onReceive method, which receives Context and Intent parameters.

The BroadcastReceiver class is well-described in the official documentation, which is why we won’t focus on its properties.

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Reading and decrypting SMS messages

After we’ve created encryption procedures, it’s time to add functionality for reading and decrypting SMS messages. Let’s list the click listener for the button on the main screen. All texts from the inbox are read, and then the sender information and SMS text are put into the list.

Conclusion

An application for handling text messages is must on any device. Lots of users aren’t satisfied with their default SMS app and are looking for a more comfortable solution. But there are several tricks to developing an SMS app. It has to:

  • be the default application for SMS messages
  • ask for all necessary permissions (and not crash it a user denies them)
  • receive, display, and allow the user to respond to texts
  • be secure
  • add received texts to the device’s SMS database

In this article, we’ve shown you how to build an Android app with this functionality. Creating such applications is only the tip of the iceberg in terms of our experience in mobile app development. If you have a complex Android-related project, challenge us with it!