Flutter Meets Go

A Flutter application that demonstrates how to integrate Go code with Flutter using Foreign Function Interface (FFI).

Overview

demo.mp4

This project showcases how to leverage Go's powerful features within a Flutter application through FFI (Foreign Function Interface). As a practical example, the app allows users to enter a GitHub username and fetch their profile avatar using a Go function that makes HTTP requests.

How It Works

1. Flutter UI: The app provides a simple interface where users can enter a GitHub username and click a button to fetch the avatar.

2. Go Backend: A Go function (GetGithubAvatar) handles the HTTP request to GitHub's API to retrieve the user's avatar image.

3. FFI Bridge: Flutter communicates with the Go code through FFI, allowing seamless integration between the two languages.

Technical Details

Flutter Side

• Uses Dart FFI to call the compiled Go function
• Handles the UI and user interactions
• Processes and displays the returned image data

Go Side

• Makes HTTP requests to GitHub's API
• Processes the response and extracts the avatar image
• Returns the image data back to Flutter

Getting Started

Prerequisites

• Flutter SDK
• Go compiler
• FFI package for Flutter
• Android NDK or Xcode for compilation

Building the Go Library

For Android

First, create the necessary jniLibs directories if they don't exist:

mkdir -p android/app/src/main/jniLibs/arm64-v8a
mkdir -p android/app/src/main/jniLibs/armeabi-v7a
mkdir -p android/app/src/main/jniLibs/x86
mkdir -p android/app/src/main/jniLibs/x86_64

Then build for each architecture:

# For arm64
GOOS=android GOARCH=arm64 CGO_ENABLED=1 CC=$ANDROID_NDK_HOME/toolchains/llvm/prebuilt/darwin-x86_64/bin/aarch64-linux-android21-clang go build -buildmode=c-shared -o android/app/src/main/jniLibs/arm64-v8a/github_avatar.so go_files/github_avatar.go

# For arm
GOOS=android GOARCH=arm CGO_ENABLED=1 CC=$ANDROID_NDK_HOME/toolchains/llvm/prebuilt/darwin-x86_64/bin/armv7a-linux-androideabi21-clang go build -buildmode=c-shared -o android/app/src/main/jniLibs/armeabi-v7a/github_avatar.so go_files/github_avatar.go

# For x86
GOOS=android GOARCH=386 CGO_ENABLED=1 CC=$ANDROID_NDK_HOME/toolchains/llvm/prebuilt/darwin-x86_64/bin/i686-linux-android21-clang go build -buildmode=c-shared -o android/app/src/main/jniLibs/x86/github_avatar.so go_files/github_avatar.go

# For x86_64
GOOS=android GOARCH=amd64 CGO_ENABLED=1 CC=$ANDROID_NDK_HOME/toolchains/llvm/prebuilt/darwin-x86_64/bin/x86_64-linux-android21-clang go build -buildmode=c-shared -o android/app/src/main/jniLibs/x86_64/github_avatar.so go_files/github_avatar.go

Note: The path to your NDK might be different. Adjust accordingly.

For iOS

go build -buildmode=c-archive -o ios/Runner/github_avatar.a go_files/github_avatar.go

After generating the .a file, you'll need to add it to your Xcode project:

1. Open the iOS project in Xcode
2. Drag the github_avatar.a and github_avatar.h files into your project
3. Add the library to "Link Binary With Libraries" in your target's Build Phases

For Linux/macOS/Windows Development

go build -buildmode=c-shared -o github_avatar.so go_files/github_avatar.go

Running the Flutter App

1. Ensure the Go shared library is in the correct location
2. Run the Flutter app:

   flutter run
   

Project Structure

• lib/github_avatar.dart: Contains the Dart FFI bindings to call the Go function
• lib/main.dart: The main Flutter application
• go_files/github_avatar.go: The Go code that fetches GitHub avatars

Usage

// Import the GitHub avatar library
import 'github_avatar.dart';

// Fetch an avatar
final avatarBytes = GithubAvatar.getAvatar('username');

// Display it
if (avatarBytes.isNotEmpty) {
  Image.memory(avatarBytes)
}

Performance Benefits

FFI provides several advantages over Method Channel:

• Direct Memory Access: No serialization/deserialization overhead
• Reduced Context Switching: Calls happen within the same thread context
• Lower Latency: Significantly faster for large data transfers like images
• No Message Passing: Avoids the overhead of passing messages between isolates

License

This project is open source and available under the MIT License.