Fixing Critical Tamara Flutter SDK Issues: Java Version Conflicts and Concurrency Crashes

Two essential workarounds for Flutter developers using Tamara SDK until official fixes are released

If you're integrating the Tamara Flutter SDK into your app and running into mysterious build failures or random crashes, you're not alone. After wrestling with these issues in production, I've discovered two critical problems with the current Tamara SDK and their workarounds.

The Problems

The Tamara Flutter SDK (tamara_flutter_sdk: ^1.0.17) has two major issues that can break your Flutter app:

1. Java Version Compatibility Issues - Build failures due to JVM target mismatches
2. Concurrency Crashes - App crashes when multiple SDK calls happen simultaneously

Let's dive into each problem and how to fix them.

Problem #1: Java Version Compatibility Hell

The Error You'll See

If you're lucky enough to get a clear error message, it looks like this:

* What went wrong:
Execution failed for task ':tamara_flutter_sdk:kaptGenerateStubsDebugKotlin'.
> Error while evaluating property 'compilerOptions.jvmTarget' of task ':tamara_flutter_sdk:kaptGenerateStubsDebugKotlin'.
   > Failed to calculate the value of property 'jvmTarget'.
      > Unknown Kotlin JVM target: 21
        

What's Actually Happening

The Tamara SDK is compiled with Java 21, but your Flutter project is likely using Java 11 or 17. This creates a bytecode incompatibility that breaks the build process, specifically during Kotlin annotation processing (kapt).

The Fix: Root-Level Java Version Enforcement

The solution isn't just changing your app's Java version - you need to force all subprojects (including the Tamara SDK) to use the same Java version.

Add this to your /android/build.gradle file:

// Apply consistent Kotlin and Java JVM target across all modules
subprojects {
    tasks.withType(org.jetbrains.kotlin.gradle.tasks.KotlinCompile).configureEach {
        kotlinOptions {
            jvmTarget = "17"
        }
    }
    tasks.withType(JavaCompile).configureEach {
        sourceCompatibility = "17"
        targetCompatibility = "17"
    }
}

subprojects { proj ->
    proj.afterEvaluate {
        def androidExt = proj.extensions.findByName("android")
        if (androidExt != null) {
            androidExt.compileOptions {
                sourceCompatibility JavaVersion.VERSION_17
                targetCompatibility JavaVersion.VERSION_17
            }
        }
    }
}
        

Why This Works

• Overrides Plugin Settings: Forces the Tamara SDK to compile with Java 17 instead of Java 21
• Ensures Consistency: All modules use the same Java version, preventing bytecode conflicts
• Uses afterEvaluate: Applies after all plugins have configured themselves
• Future-Proof: Handles any other plugins with similar issues

Problem #2: The Mysterious Concurrency Crash

The Problem

This one's sneaky. If you have multiple Tamara widgets on the same screen or call Tamara SDK functions multiple times quickly, your app will crash without a clear error message.

The issue is in the native Android plugin - when multiple concurrent requests try to deliver onActivityResult callbacks, the plugin crashes.

The Fix: Mutex Implementation

Create a mutex to serialize all Tamara SDK calls. Here's the implementation:

import 'dart:async';

class _TamaraMutex {
  static Completer<void>? _lock;

  /// Runs [action] after waiting for any currently-running action to finish.
  static Future<T> runLocked<T>(Future<T> Function() action) async {
    // Simple spin-wait: if another call is in progress, await its completer.
    while (_lock != null) {
      await _lock!.future; // wait until the previous call completes
    }

    // Claim the lock
    _lock = Completer<void>();
    try {
      return await action();
    } finally {
      // Release the lock and notify any waiters
      _lock!.complete();
      _lock = null;
    }
  }
}
        

How to Use It

Wrap all your Tamara SDK calls with the mutex:

Future<void> _loadTamaraData() async {
  try {
    // Ensure only one TamaraSdk call is in flight globally
    final String result = await _TamaraMutex.runLocked(() async {
      return TamaraSdk.renderProduct(
        language,
        'sa',
        apiKey,
        amount,
      );
    });

    // Process the result...
  } catch (e) {
    log('Error loading Tamara widget: $e');
  }
}
        

Why This Works

• Global Serialization: All Tamara widgets share the same mutex
• Prevents Native Conflicts: Only one SDK call happens at a time
• Transparent to Users: The delay is imperceptible in the UI
• Error Safe: Lock is released even if the SDK call throws an exception

Complete Example Implementation

Here's how I implemented both fixes in a reusable Tamara widget:

abstract class BaseTamaraWidget extends StatefulWidget {
  final String language;
  final double amount;
  final double height;

  const BaseTamaraWidget({
    super.key,
    required this.language,
    required this.amount,
    required this.height,
  });
}

abstract class BaseTamaraWidgetState<T extends BaseTamaraWidget>
    extends State<T> {
  late WebViewController _controller;
  TamaraData? _data;

  @override
  void initState() {
    super.initState();
    _initWebView();
    _loadData();
  }

  Future<String> getTamaraData(); // Implement in subclasses

  Future<void> _loadData() async {
    try {
      // Use mutex to prevent concurrent SDK calls
      final String result = await _TamaraMutex.runLocked(getTamaraData);

      if (!mounted) return;

      // Process and display the result...
      final data = TamaraData.fromJson(jsonDecode(result));
      setState(() => _data = data);

      _controller.loadHtmlString(createHtmlContent(data.script));
    } catch (e) {
      log('Error loading Tamara widget: $e');
    }
  }

  // Rest of your widget implementation...
}
        

Testing Your Fixes

After implementing both solutions, verify:

• ✅ Build Success: flutter build apk completes without errors
• ✅ Multiple Widgets: Several Tamara widgets can coexist on the same screen
• ✅ Rapid Navigation: Quickly navigating between screens with Tamara widgets doesn't crash
• ✅ Production Stability: No more mysterious crashes in production

Why These Issues Exist

These problems stem from:

1. SDK Compilation Environment: The Tamara team likely uses a newer Java version than most Flutter projects
2. Native Plugin Architecture: Flutter's native plugin system doesn't handle concurrent calls well
3. Insufficient Testing: These edge cases weren't caught in the SDK's testing process

The Bottom Line

While waiting for official fixes from the Tamara team, these workarounds will keep your app stable and your users happy. Both solutions are:

• Production-tested ✅
• Minimal performance impact ✅
• Easy to remove when official fixes arrive ✅
• Compatible with other Flutter plugins ✅

What's Next?

I've documented these issues and shared them with the Tamara team. Hopefully, future SDK versions will address these problems at the source. Until then, these workarounds will keep your Flutter app running smoothly.

Have you encountered other issues with the Tamara Flutter SDK? Share your experiences in the comments below!

Tags: #Flutter #TamaraSDK #AndroidDevelopment #PaymentIntegration #BugFix #TechnicalDebt

Resources

• Tamara Flutter SDK Documentation
• Flutter Android Build Configuration
• Kotlin JVM Target Configuration

This article is based on real production experience with Tamara SDK version 1.0.17. Solutions may need adjustment for different versions.