Native interop rewrite by lamek · Pull Request #13462 · flutter/website

lamek · 2026-06-05T01:10:47Z

Updates #13115

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Removed placeholder for diagram and extra line breaks.

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

gemini-code-assist

Code Review

This pull request introduces comprehensive documentation and guides for direct native interop in Flutter, including new pages on using jnigen for Android, ffigen for iOS, and a comparison of platform integration options. The review feedback identifies several critical issues in the code snippets, such as a guaranteed runtime crash in the iOS FFI example due to incorrect string casting, missing configuration classes in the jnigen setup causing compilation failures, multiple JNI local reference memory leaks in the Android permissions example, duplicated Groovy dependencies, and syntax errors from missing closing braces. Addressing these issues will ensure the code examples are safe, correct, and idiomatic.

gemini-code-assist · 2026-06-05T01:12:32Z

+      classes: [
+        // provided by Android OS
+        'android.os.Bundle',
+        'android.content.Intent',
+        'android.content.Context'
+      ],


The custom SecondActivity Kotlin class is missing from the classes list in tool/jnigen.dart. Without adding it here, jnigen will not generate the Dart bindings for SecondActivity, causing the Dart compilation to fail on line 125 when referencing native.SecondActivity.type.jClass.

Suggested change

classes: [

// provided by Android OS

'android.os.Bundle',

'android.content.Intent',

'android.content.Context'

],

classes: [

// provided by Android OS

'android.os.Bundle',

'android.content.Intent',

'android.content.Context',

'com.example.android_launch_activity.SecondActivity'

],

gemini-code-assist · 2026-06-05T01:12:32Z

+
+// Context.fromReference ensures we get Android Context object
+// rather than the default `JObject`
+var context = native.Context.fromReference(Jni.androidApplicationContext.reference);


Instead of manually accessing the low-level .reference property and calling fromReference, you can use the more idiomatic .as() extension method on JObject to cast the context to native.Context. This matches the modern style used in jnigen.md.

Suggested change

var context = native.Context.fromReference(Jni.androidApplicationContext.reference);

var context = Jni.androidApplicationContext.as(native.Context.type);

gemini-code-assist · 2026-06-05T01:12:32Z

+  int checkAndRequestPermission(
+    JObject context,
+    String permission,
+    Function callback,
+  ) {
+    // Do I have permission?
+    if (ContextCompat.checkSelfPermission(context, permission.toJString()) ==
+        PackageManager.PERMISSION_GRANTED) {
+      callback();
+    } else if (ActivityCompat.shouldShowRequestPermissionRationale(
+          Jni.androidActivity(PlatformDispatcher.instance.engineId!),
+          permission.toJString(),
+        ) ==
+        true) {
+      // Has the user denied the permission before?
+      // Give a reason why I need the permission
+      // and allow a re-request
+      print("I should ask for permission");
+      // TODO Flow to show UI to reshow perms dialog
+      return -2;
+    } else {
+      // Ask for permission
+      ActivityCompat.requestPermissions(
+        Jni.androidActivity(PlatformDispatcher.instance.engineId!),
+        JArray.of(JString.type, [permission.toJString()]),
+        0,
+      );
+    }
+    return 0;
+  }


In checkAndRequestPermission, permission.toJString() is called up to three times, creating multiple JNI local references that are never released. It is much more efficient and leak-safe to convert the string once, use the variable, and release it in a finally block.

int checkAndRequestPermission( JObject context, String permission, Function callback, ) { final jPermission = permission.toJString(); try { // Do I have permission? if (ContextCompat.checkSelfPermission(context, jPermission) == PackageManager.PERMISSION_GRANTED) { callback(); } else if (ActivityCompat.shouldShowRequestPermissionRationale( Jni.androidActivity(PlatformDispatcher.instance.engineId!), jPermission, ) == true) { // Has the user denied the permission before? // Give a reason why I need the permission // and allow a re-request print("I should ask for permission"); // TODO Flow to show UI to reshow perms dialog return -2; } else { // Ask for permission ActivityCompat.requestPermissions( Jni.androidActivity(PlatformDispatcher.instance.engineId!), JArray.of(JString.type, [jPermission]), 0, ); } return 0; } finally { jPermission.release(); } }

lamek · 2026-06-05T01:13:08Z

@jwill this is draft (v2) of the Interop rewrite.

I still need to test the ffigen tutorial for iOS.

I could use some extra attention on the table to help devs choose an Interop solution: https://github.com/flutter/website/pull/13462/changes#diff-39b4cf53fbefc7c1e7d95424eaea65acb9a711a8a0473ed816ff4474123220a6R15

flutter-website-bot · 2026-06-05T01:18:16Z

Visit the preview URL for this PR (updated for commit b52b94c):

https://flutter-docs-prod--pr13462-native-interop-rewrite-je6br604.web.app

lamek · 2026-06-05T15:45:32Z

I'm iterating on the ffigen tutorial but I can't get the generated code to work with the example code. I might have to rework this tutorial to use a much simpler example.

sfshaza2 · 2026-06-08T17:04:21Z

Thanks for closing that old PR!!! Once the code changes have been made and approved (by both Gemini and a DRE). I'm good!

…l with assets

flutter-website-bot · 2026-06-12T20:57:13Z

Staged preview of the updated docs.flutter.dev site (updated for commit 52f63ad):

https://flutter-docs-prod--docs-pr13462-native-interop-rewrite-wju7kso6.web.app

Remove duplicated dependencies block Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

flutter-website-bot · 2026-06-13T01:20:54Z

Staged preview of the updated flutter.dev site (updated for commit 52f63ad):

https://flutter-dev-230821--www-pr13462-native-interop-rewrite-h2p0zkrz.web.app

Fixed link that was preventing dash_site from checking the links.

Added redirect for the "call-jetpack-apis" page to "jnigen" and verified with check links.

It is based on the ios calendar demo in flutter/demos

sfshaza2

In general, this PR:

Doesn't use semantic line breaks (many lines break 80-char limit)
Uses first person (don't use "we" or "our" or "I", use "you" or "your", etc)
Fails to use sentence casing in several places
Uses "will" (future tense) unnecessarily

All of these are listed in the Developer Documentation Style Guidelines.

Also, this PR fails to use our URL macros.

sfshaza2 · 2026-06-18T17:39:13Z

+On the Flutter side, you will need to create Dart bindings for various Android APIs 
+and call them using Dart code. This will involve setting up `jni`, `jnigen`,
+and a configuration file describing the generated output.


Suggested change

On the Flutter side, you will need to create Dart bindings for various Android APIs

and call them using Dart code. This will involve setting up `jni`, `jnigen`,

and a configuration file describing the generated output.

On the Flutter side, you need to create Dart bindings for various Android APIs

and call them using Dart code. This involves setting up `jni`, `jnigen`,

and a configuration file describing the generated output.

sfshaza2 · 2026-06-18T17:39:36Z

+
+The [code][] for this version is available on Github.
+
+[code]:https://github.com/flutter/demos/tree/main/native_interop_demos/android_launch_activity


Suggested change

[code]:https://github.com/flutter/demos/tree/main/native_interop_demos/android_launch_activity

[code]: {{site.github}}/flutter/demos/tree/main/native_interop_demos/android_launch_activity

sfshaza2 · 2026-06-18T17:39:59Z

+
+## Overview of launching Activities using Method Channels
+
 On the Flutter side, you will need to create a new


Suggested change

On the Flutter side, you will need to create a new

On the Flutter side, you need to create a new

sfshaza2 · 2026-06-18T17:40:12Z

 On the Flutter side, you will need to create a new
 platform method channel and call its `invokeMethod` method.
+
 On the Android side, you will need to register a matching native `MethodChannel`


Suggested change

On the Android side, you will need to register a matching native `MethodChannel`

On the Android side, you need to register a matching native `MethodChannel`

sfshaza2 · 2026-06-18T17:40:48Z

+### On the command line
+
+On the commandline, add `jnigen` as a development dependency
+and `jni` as a runtime dependency. `jnigen` will be used to


Suggested change

and `jni` as a runtime dependency. `jnigen` will be used to

and `jni` as a runtime dependency. `jnigen` is used to

sfshaza2 · 2026-06-18T17:57:53Z

+
+## Conclusion
+
+You have successfully built a Flutter application that interacts directly with iOS APIs! By using `ffigen` and `objective_c`, you can skip writing manual message channels and focus on building high quality Dart code.


Suggested change

You have successfully built a Flutter application that interacts directly with iOS APIs! By using `ffigen` and `objective_c`, you can skip writing manual message channels and focus on building high quality Dart code.

You have successfully built a Flutter application that interacts directly with iOS APIs!

By using `ffigen` and `objective_c`, you can skip writing manual message channels

and focus on building high quality Dart code.

sfshaza2 · 2026-06-18T17:58:38Z

+
+## Plugins
+
+We recommend checking [pub.dev](https://pub.dev) first


Suggested change

We recommend checking [pub.dev](https://pub.dev) first

We recommend checking [pub.dev]({{site.pub}}) first

sfshaza2 · 2026-06-18T17:59:02Z

+
+## Custom solutions
+
+If a package does not support your desired feature on pub.dev,


Suggested change

If a package does not support your desired feature on pub.dev,

If a package does not support your desired feature on `pub.dev`,

sfshaza2 · 2026-06-18T18:12:25Z

+and executes native code on the UI thread.
+
+To create compilation bindings automatically,
+use generator tools like [`ffigen`](https://pub.dev/packages/ffigen)


Suggested change

use generator tools like [`ffigen`](https://pub.dev/packages/ffigen)

use generator tools like [`ffigen`]({{site.pub-pkg}}/ffigen)

sfshaza2 · 2026-06-18T18:13:08Z

+To create compilation bindings automatically,
+use generator tools like [`ffigen`](https://pub.dev/packages/ffigen)
+(for C, Objective-C, and Swift)
+or [`jnigen`](https://pub.dev/packages/jnigen) (for Java and Kotlin on Android).


Suggested change

or [`jnigen`](https://pub.dev/packages/jnigen) (for Java and Kotlin on Android).

or [`jnigen`]({{site.pub-pkg}}/jnigen) (for Java and Kotlin on Android).

jwill and others added 8 commits February 24, 2026 20:00

Draft of some possible native interop updates

64599ea

Update compose-activity.md

5b2dd83

Update src/content/platform-integration/android/compose-activity.md

158cd1a

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Update src/content/platform-integration/android/compose-activity.md

e97fcb8

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Clean up jnigen.md by removing unused content

43a288f

Removed placeholder for diagram and extra line breaks.

Apply suggestion from @gemini-code-assist[bot]

bc7d973

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Apply suggestion from @gemini-code-assist[bot]

d219e50

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Apply suggestions from code review

61c5f44

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

lamek requested review from a team and sfshaza2 as code owners June 5, 2026 01:10

lamek mentioned this pull request Jun 5, 2026

Documenting some native interop things. #13115

Closed

4 tasks

gemini-code-assist Bot reviewed Jun 5, 2026

View reviewed changes

lamek requested a review from jwill June 5, 2026 01:13

lamek mentioned this pull request Jun 5, 2026

docs: add agent skills playbook for technical writers #13463

Closed

lamek added 2 commits June 12, 2026 19:52

Merge branch 'pr-13115' into native-interop-rewrite

08ca6ca

docs: restructure native interop options and modernize jnigen tutoria…

ecc2329

…l with assets

lamek force-pushed the native-interop-rewrite branch from b52b94c to ecc2329 Compare June 12, 2026 20:50

flutter deleted a comment from flutter-website-bot Jun 13, 2026

jwill and others added 3 commits June 12, 2026 18:09

Apply suggestion from @gemini-code-assist[bot]

3246afb

Remove duplicated dependencies block Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Apply suggestion from @gemini-code-assist[bot]

7450cb8

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Apply suggestion from @gemini-code-assist[bot]

c5a63b6

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

jwill added 3 commits June 12, 2026 18:57

Update index.md

7a10d86

Fixed link that was preventing dash_site from checking the links.

Update firebase.json

11a4af2

Added redirect for the "call-jetpack-apis" page to "jnigen" and verified with check links.

Update firebase.json

6799959

Add a draft of an ios demo at /platform-integration/ios/ffigen

52f63ad

It is based on the ios calendar demo in flutter/demos

sfshaza2 reviewed Jun 18, 2026

View reviewed changes

	var context = native.Context.fromReference(Jni.androidApplicationContext.reference);
	var context = Jni.androidApplicationContext.as(native.Context.type);


		The [code][] for this version is available on Github.

		[code]:https://github.com/flutter/demos/tree/main/native_interop_demos/android_launch_activity

	[code]:https://github.com/flutter/demos/tree/main/native_interop_demos/android_launch_activity
	[code]: {{site.github}}/flutter/demos/tree/main/native_interop_demos/android_launch_activity


		## Overview of launching Activities using Method Channels

		On the Flutter side, you will need to create a new

	On the Flutter side, you will need to create a new
	On the Flutter side, you need to create a new

	On the Android side, you will need to register a matching native `MethodChannel`
	On the Android side, you need to register a matching native `MethodChannel`

	and `jni` as a runtime dependency. `jnigen` will be used to
	and `jni` as a runtime dependency. `jnigen` is used to


		## Conclusion

		You have successfully built a Flutter application that interacts directly with iOS APIs! By using `ffigen` and `objective_c`, you can skip writing manual message channels and focus on building high quality Dart code.


		## Plugins

		We recommend checking [pub.dev](https://pub.dev) first

	We recommend checking [pub.dev](https://pub.dev) first
	We recommend checking [pub.dev]({{site.pub}}) first


		## Custom solutions

		If a package does not support your desired feature on pub.dev,

	use generator tools like [`ffigen`](https://pub.dev/packages/ffigen)
	use generator tools like [`ffigen`]({{site.pub-pkg}}/ffigen)

	or [`jnigen`](https://pub.dev/packages/jnigen) (for Java and Kotlin on Android).
	or [`jnigen`]({{site.pub-pkg}}/jnigen) (for Java and Kotlin on Android).

Conversation

lamek commented Jun 5, 2026

Uh oh!

gemini-code-assist Bot left a comment

Choose a reason for hiding this comment

Code Review

Uh oh!

Uh oh!

gemini-code-assist Bot Jun 5, 2026

Choose a reason for hiding this comment

Uh oh!

gemini-code-assist Bot Jun 5, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

gemini-code-assist Bot Jun 5, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

lamek commented Jun 5, 2026

Uh oh!

flutter-website-bot commented Jun 5, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

lamek commented Jun 5, 2026

Uh oh!

sfshaza2 commented Jun 8, 2026

Uh oh!

flutter-website-bot commented Jun 12, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

flutter-website-bot commented Jun 13, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

sfshaza2 left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

flutter-website-bot commented Jun 5, 2026 •

edited

Loading

flutter-website-bot commented Jun 12, 2026 •

edited

Loading

flutter-website-bot commented Jun 13, 2026 •

edited

Loading