Documenting some native interop things. by jwill · Pull Request #13115 · flutter/website

jwill · 2026-02-25T04:08:27Z

Description of what this PR is changing or adding, and why:

This is PR is reimagining some of the Platform Integration section for demonstration purposes. Consider it a draft to advance the conversation.

Issues fixed by this PR (if any):

PRs or commits this PR depends on (if any):

Presubmit checklist

If you are unwilling, or unable, to sign the CLA, even for a tiny, one-word PR, please file an issue instead of a PR.
If this PR is not meant to land until a future stable release, mark it as draft with an explanation.
This PR follows the Google Developer Documentation Style Guidelines—for example, it doesn't use i.e. or e.g., and it avoids I and we (first-person pronouns).
This PR uses semantic line breaks
of 80 characters or fewer.

gemini-code-assist · 2026-02-25T04:08:46Z

Summary of Changes

Hello @jwill, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly expands and refines the documentation for Android platform integration within Flutter. It introduces jnigen as a key tool for direct native interop, providing detailed guides for common use cases like launching activities and managing permissions. The changes aim to offer clearer, more up-to-date pathways for developers to interact with native Android functionalities, alongside a new overview of available interop options and improved navigation.

Highlights

New Native Interop Documentation: Introduced new documentation pages detailing how to use jnigen for calling native Android APIs and requesting permissions from Flutter, providing a modern approach to platform integration.
Updated Android Activity Launch Guide: Revised the guide for launching Android activities to include jnigen as an alternative to traditional Method Channels, offering comprehensive steps for both methods.
Overview of Platform-Specific Code Options: Added a new page that outlines various strategies for integrating platform-specific code, including FFI/JNI, self-managed platform channels, and Pigeon, along with guidance on when to use each.
Navigation Restructuring: Updated the site's navigation (default.yml) to incorporate the new documentation and clarify existing entries related to platform integration.
New JNI Call Lifecycle Diagrams: Added SVG diagrams illustrating the Java Native Interface (JNI) call lifecycle for both dark and light themes to enhance visual understanding of the process.

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Changelog

site/web/assets/images/android/jni-call-lifecycle-dark.svg
- Added a new SVG diagram illustrating the JNI call lifecycle for dark themes.
site/web/assets/images/android/jni-call-lifecycle-light.svg
- Added a new SVG diagram illustrating the JNI call lifecycle for light themes.
src/content/platform-integration/android/call-jetpack-apis.md
- Renamed to src/content/platform-integration/android/call-native-apis.md.
- Updated title and description to reflect a broader scope of calling native APIs.
src/content/platform-integration/android/compose-activity.md
- Updated content to introduce jnigen as an alternative to Method Channels for launching activities.
- Provided detailed steps for configuring jnigen and modifying Android build files and manifest.
- Added code examples for jnigen setup and Dart-side calls.
src/content/platform-integration/android/jnigen.md
- Added a new documentation page explaining jnigen for calling native Android APIs.
- Included sections on jnigen setup, configuration, and calling Dart bindings with examples like displaying a Toast message.
src/content/platform-integration/android/request-permission.md
- Added a new documentation page detailing how to request Android permissions using jnigen within a Flutter plugin.
- Provided jnigen setup and plugin implementation details, along with usage examples.
src/content/platform-integration/native-code-options.md
- Added a new documentation page outlining different options for calling platform-specific code (FFI/JNI, self-managed platform channels, Pigeon).
- Included guidance on when to choose each interop method based on specific use cases.
src/content/platform-integration/platform-channels.md
- Updated the title and short title to better reflect its focus on message passing for platform-specific code.
src/data/sidenav/default.yml
- Modified the navigation structure to include new documentation pages.
- Updated titles for existing platform integration topics to improve clarity and organization.

Activity

jwill created this pull request with the intent to reimagine and advance the conversation around the Platform Integration section documentation.

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Code Review

This PR significantly refactors the documentation around native platform integration, introducing jnigen as a primary way to interact with native Android code. It adds several new pages explaining jnigen and providing examples for launching activities and requesting permissions. The existing documentation is updated to reflect this new structure. Overall, this is a great improvement to the documentation. I've found a few issues, mostly in the code snippets within the markdown files, such as duplicated dependencies and incorrect language tags for code blocks. There are also some minor typos and inconsistencies that should be addressed to improve clarity.

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

gemini-code-assist · 2026-02-25T04:12:12Z

src/content/platform-integration/android/jnigen.md

+
+The APISummarizer is a tool that reads source and bytecode to determine which classes and functions are present. The abstract syntax tree defining the desired classes is read to create Dart versions with modifications to account for the differences between the Java platform and Dart.
+
+Diagram should go here


This placeholder text should be removed since the diagram has been added below.

src/content/platform-integration/android/jnigen.md

gemini-code-assist · 2026-02-25T04:12:13Z

src/content/platform-integration/android/request-permission.md

+        'androidx.activity.result.ActivityResultLauncher',
+        'androidx.activity.result.contract.ActivityResultContract',
+        'android.content.Intent',
+        //'android.content.Context',


This class is commented out in the list of classes for jnigen. If it's not needed for the example, it would be clearer to remove it to avoid confusion.

src/content/platform-integration/native-code-options.md

src/data/sidenav/default.yml

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

flutter-website-bot · 2026-02-25T04:13:53Z

Visit the preview URL for this PR (updated for commit d219e50):

https://flutter-docs-prod--pr13115-native-interop-things-pya9nu29.web.app

Removed placeholder for diagram and extra line breaks.

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

lamek

Some style updates, a few nits, and 2 suggestions. Looking really good. I'll have more higher level perspective as I come up to speed on interop.

lamek · 2026-03-09T15:15:52Z

src/content/platform-integration/native-code-options.md

+---
+title: Writing custom platform-specific code
+shortTitle: Platform-specific code
+description: Learn how about the options to call platform specific code in your app.


Remove "how". Update to "platform-specific".

lamek · 2026-03-09T15:16:48Z

src/content/platform-integration/native-code-options.md

+
+## Overview
+
+You have a number of options to use platform-specific code 


Suggestion: break this up.
"You have several options for using platform-specific code in your Dart and Flutter apps. These range from low-level options requiring deep knowledge of the host language, to high-level options that abstract the native components behind an API."

lamek · 2026-03-09T15:17:45Z

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

+
+Execute `dart run tool/jnigen.dart` to generate the Dart bindings.
+
+With the bindings generated, we can directly


Complete this sentence.

"...directly call them in your Dart code."

Change "we" --> "you".

Can you ctrl-f for "we " (do we with the space). There are 4 instances throughout.

lamek · 2026-03-09T15:18:10Z

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

+
+### On the command line
+
+On the commandline, add `jnigen` as a development dependency


command line

lamek · 2026-03-09T15:18:26Z

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

+On the Android side, you will need to make some modifications to some Android build
+files to account for Compose views and a new `Activity`. 
+
+The [code][] for this version is available on Github.


nit: GitHub

lamek · 2026-03-09T15:18:56Z

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

+
+### On the Dart side
+
+In your dart code, create jnigen.dart file specifying the


nit: capital "D": "Dart code"

lamek · 2026-03-09T15:19:48Z

src/content/platform-integration/android/jnigen.md

+```
+
+### Step 3: Set configuration of Dart bindings
+There is a Dart API in `jnigen` to specify the properties your generated should have. You will create


Missing word - "code".

"...specify the properties your generated code should have."

lamek · 2026-03-09T15:20:41Z

src/content/platform-integration/android/jnigen.md

+Here is the full `main.dart` file.
+
+:::note
+Java/Kotlin and Dart differ on support of overloaded functions, that's to say functions that use the same


Suggestion: rephrase this.

"Java/Kotlin and Dart differ in their support for overloaded functions (functions that share a name but have different return types or parameters)."

lamek · 2026-03-09T15:21:27Z

src/content/platform-integration/android/request-permission.md

+This page details a means to use `jnigen` to wrap native Android code and package that functionality
+as a plugin. It demonstrates requesting and querying Android permissions natively from Flutter.
+
+With this flow, one only has to edit a single file on the Android side.


I wouldn't use "one only" (I get what you're saying).

Try "you only need to..." instead.

jwill added 2 commits February 24, 2026 20:00

Draft of some possible native interop updates

64599ea

Update compose-activity.md

5b2dd83

jwill assigned lamek Feb 25, 2026

jwill requested review from a team and sfshaza2 as code owners February 25, 2026 04:08

gemini-code-assist bot reviewed Feb 25, 2026

View reviewed changes

jwill and others added 2 commits February 24, 2026 20:12

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>

jwill and others added 4 commits February 24, 2026 20:14

Clean up jnigen.md by removing unused content

43a288f

Removed placeholder for diagram and extra line breaks.

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

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sfshaza2 requested a review from lamek February 25, 2026 05:36

lamek reviewed Mar 9, 2026

View reviewed changes


		The APISummarizer is a tool that reads source and bytecode to determine which classes and functions are present. The abstract syntax tree defining the desired classes is read to create Dart versions with modifications to account for the differences between the Java platform and Dart.

		Diagram should go here


		## Overview

		You have a number of options to use platform-specific code


		Execute `dart run tool/jnigen.dart` to generate the Dart bindings.

		With the bindings generated, we can directly


		### On the command line

		On the commandline, add `jnigen` as a development dependency


		### On the Dart side

		In your dart code, create jnigen.dart file specifying the

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jwill commented Feb 25, 2026

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flutter-website-bot commented Feb 25, 2026 •

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