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Swift on Android: JNIKit 2.11.0: Automatic Memory & 2D Arrays


This content originally appeared on DEV Community and was authored by Mikhail Isaev

The ecosystem for Swift on Android just got a significant upgrade with the release of JNIKit 2.11.0. This library simplifies JNI interaction, and this latest version focuses on two major pain points: robust memory management and expanded data structure support.

Automatic Memory Control

The days of manually managing JNI references are over.

  • JObject now automatically deletes its underlying jobject on deinit.
  • This logic has been extended to JClass, JClassLoader, and JObjectArray.
  • Key Takeaway: You can now rely entirely on Swift’s deinit for memory management. No more manual deletion or worrying about reference leaks.

Note for Upgraders: This is a breaking change if you previously handled memory manually. Also, the internal method env.callObjectMethodPure has been updated—check the release notes if you use it directly.

1D & 2D Array Support

Working with Java arrays is now more Swift-like than ever.

1D Arrays (e.g., [Int8], [Float], [Double]):

  • Easy initialization from a Swift Array: JIntArray([1, 2, 3])
  • Efficient iteration to avoid copying large arrays: 
for value in intArray {
    Log.d("value: \(value)")
}

New: 2D Array Support! 🎉 (e.g., [[Int32]], [[Double]])
This is crucial for many Android APIs (like ColorStateList).

  • Initialize directly from a nested Swift array: JIntArray2D([[1, 2, 3], [4, 5, 6]])
  • Iterate or convert back to a Swift array with ease.

Passing arrays to Java methods is now trivial:

// No need to manually create wrapper objects
object.callVoidMethod(name: "send1DArray", args: [1, 2, 3])
object.callVoidMethod(name: "send2DArray", args: [[1, 2, 3], [4, 5, 6]])

Enhanced Debugging

Logging for global reference creation/deletion has been greatly improved, making it easier to trace memory issues during development.

Links:

If you find JNIKit useful, giving it a star on GitHub helps others discover it and supports the project!

I’m happy to answer any questions and hear about your experiences using Swift for Android.


This content originally appeared on DEV Community and was authored by Mikhail Isaev