🔐 Flutter OTP Auto Field

A complete OTP solution for Flutter apps — auto-listen, extract, and display OTPs using Android's SMS Retriever API and iOS QuickType autofill. Includes a fully customizable OTP input field with familiar Container-style decoration support.

💡 Why Use This Package?

Unlike other packages that solve only one part of OTP autofill, flutter_otp_auto_field offers:

✅ OTP Reading via Native APIs (Android & iOS)

✅ App Signature Hash Generator for Android (for SMS Retriever API)

✅ Built-in OTP Input Field with full customization

✅ Paste-friendly & Stream-based OTP Listening

✅ No SMS Permission Required (Safe for Play Store)

✨ Features

Feature	Supported
Android SMS Retriever	✅
iOS QuickType Autofill	✅
App Signature Hash	✅
OTP Stream Listener	✅
Custom OTP Field Widget	✅
Paste Support	✅
No Permissions Needed	✅

⚙️ Installation

Add to your pubspec.yaml:

dependencies:
  flutter_otp_auto_field: ^1.0.0

Then run:

flutter pub get

Android Configuration

Set minimum SDK to 19 in your app-level android/app/build.gradle:

defaultConfig {
  minSdkVersion 19
}

✅ No SMS permissions needed. ✅ Messages must include your app hash.

🧪 Usage

1. Automatically Listen to OTPs

OtpService().init(); // Start listening

OtpService().otpStream.listen((otp) {
  print("Received OTP: $otp");
});

2. Get App Signature Hash (for Android SMS)

final hash = await OtpService().getAndroidAppSignature();
print('Your App Hash: $hash');

Include this hash in your OTP SMS like:

Your OTP is 123456
<#> flutter_otp_auto_field code: 123456
$hash

FlutterOtpAutoField(
  length: 6,
  autoFocus: true,
  onCompleted: (value) => print("Completed: $value"),
  decoration: BoxDecoration(
    border: Border(bottom: BorderSide(color: Colors.blue)),
    borderRadius: BorderRadius.circular(12),
  ),
)

It accepts all common customization options like boxWidth, boxHeight, textStyle, obscureText, etc.

📱 iOS Support

iOS autofill works with SMS messages that follow these rules:

Must contain the word "code" or its localized equivalent.
The message should contain only one numeric sequence.
Example:
```
Your code is 123456
```

The OTP will appear in the keyboard suggestion bar automatically.

🖼 Example App

See example/lib/main.dart for a full working demo.

FlutterOtpAutoField(
  controller: myController,
  length: 6,
  onCompleted: (value) => print("OTP: $value"),
)

💬 Paste Support

If the user pastes OTP via the clipboard or from system suggestion, the widget handles it automatically — no extra handling needed!

🧼 Clean Architecture

Uses platform channels for Android/iOS native integration
Proper stream management (auto-dispose & cleanup)
Minimal setup — just init() and listen

📦 API Reference

Method	Description
`OtpService().init()`	Start OTP listener
`OtpService().otpStream`	Stream of OTP values
`OtpService().getAndroidAppSignature()`	App hash for SMS messages

🧑‍💻 Contributing

Have an idea or want to improve this package? Feel free to open an issue or pull request!

📄 License

❤️ Built With Care

This plugin was crafted to simplify OTP integration across Flutter projects — combining all necessary features in one robust, lightweight package.

Would you like me to:

✅ Generate a CHANGELOG.md ✅ Create a CONTRIBUTING.md ✅ Add a GitHub Actions workflow.yml for CI

Let me know — happy to help you polish it all for publishing on pub.dev.