android: keyboard height tracking via JNI/FFI bridge

- C bridge (keyboard_bridge.c) stores keyboard state in globals.
  Kotlin writes via JNI, Dart reads via FFI — zero async delay,
  same architecture as iOS.
- WindowInsetsAnimation.Callback tracks open/close per-frame.
- OnGlobalLayoutListener catches silent height changes (emoji
  keyboard resize, floating keyboard toggle).
- Dart animation replay stays iOS-only; Android reads native
  per-frame values directly.
- Cleaned up old Java stub, updated build.gradle for Kotlin + CMake
  with 16KB page alignment (Android 15+).
- Example app rewritten to demonstrate UxKeyboard usage.

android/build.gradle

@@ -2,33 +2,53 @@ group 'io.swipelab.ux'
 version '1.0-SNAPSHOT'
 
 buildscript {
+    ext.kotlin_version = '1.9.22'
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
 
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.2.1'
+        classpath 'com.android.tools.build:gradle:8.1.0'
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     }
 }
 
 rootProject.allprojects {
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
 }
 
 apply plugin: 'com.android.library'
+apply plugin: 'kotlin-android'
 
 android {
-    compileSdkVersion 28
+    namespace 'io.swipelab.ux'
+    compileSdk 34
 
     defaultConfig {
-        minSdkVersion 16
+        minSdk 21
-        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+        externalNativeBuild {
+            cmake {
+                cppFlags ""
+            }
+        }
     }
-    lintOptions {
+
-        disable 'InvalidPackage'
+    externalNativeBuild {
+        cmake {
+            path "src/main/jni/CMakeLists.txt"
+        }
+    }
+
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+
+    kotlinOptions {
+        jvmTarget = '1.8'
     }
 }

android/src/main/java/io/swipelab/ux/UxPlugin.java

@@ -1,25 +0,0 @@
-package io.swipelab.ux;
-
-import io.flutter.plugin.common.MethodCall;
-import io.flutter.plugin.common.MethodChannel;
-import io.flutter.plugin.common.MethodChannel.MethodCallHandler;
-import io.flutter.plugin.common.MethodChannel.Result;
-import io.flutter.plugin.common.PluginRegistry.Registrar;
-
-/** UxPlugin */
-public class UxPlugin implements MethodCallHandler {
-  /** Plugin registration. */
-  public static void registerWith(Registrar registrar) {
-    final MethodChannel channel = new MethodChannel(registrar.messenger(), "ux");
-    channel.setMethodCallHandler(new UxPlugin());
-  }
-
-  @Override
-  public void onMethodCall(MethodCall call, Result result) {
-    if (call.method.equals("getPlatformVersion")) {
-      result.success("Android " + android.os.Build.VERSION.RELEASE);
-    } else {
-      result.notImplemented();
-    }
-  }
-}

android/src/main/jni/CMakeLists.txt

@@ -0,0 +1,8 @@
+cmake_minimum_required(VERSION 3.10)
+project(ux_keyboard)
+
+add_library(ux_keyboard SHARED keyboard_bridge.c)
+target_link_libraries(ux_keyboard log)
+
+# 16KB page size support (required for Android 15+)
+target_link_options(ux_keyboard PRIVATE "-Wl,-z,max-page-size=16384")

android/src/main/jni/keyboard_bridge.c

@@ -0,0 +1,53 @@
+#include <jni.h>
+#include <stdint.h>
+
+// Shared state — Kotlin writes, Dart reads via FFI
+static double g_keyboard_height = 0;
+static double g_system_height = 0;
+static int32_t g_is_tracking = 0;
+static double g_anim_target = 0;
+static double g_anim_duration = 0;
+static int32_t g_anim_generation = 0;
+
+// --- Dart FFI reads (same signatures as iOS) ---
+
+double ux_keyboard_height(void) { return g_keyboard_height; }
+double ux_system_keyboard_height(void) { return g_system_height; }
+int32_t ux_is_tracking(void) { return g_is_tracking; }
+double ux_keyboard_anim_target(void) { return g_anim_target; }
+double ux_keyboard_anim_duration(void) { return g_anim_duration; }
+int32_t ux_keyboard_anim_gen(void) { return g_anim_generation; }
+
+// --- Stubs for Dart FFI parity with iOS ---
+
+void ux_enable_interactive_dismiss(double inset) { (void)inset; }
+void ux_disable_interactive_dismiss(void) {}
+
+// --- Kotlin JNI writes ---
+
+JNIEXPORT void JNICALL
+Java_io_swipelab_ux_KeyboardBridge_nSetHeight(JNIEnv *env, jclass cls, jdouble h) {
+    g_keyboard_height = h;
+}
+
+JNIEXPORT void JNICALL
+Java_io_swipelab_ux_KeyboardBridge_nSetSystemHeight(JNIEnv *env, jclass cls, jdouble h) {
+    g_system_height = h;
+}
+
+JNIEXPORT jdouble JNICALL
+Java_io_swipelab_ux_KeyboardBridge_nGetSystemHeight(JNIEnv *env, jclass cls) {
+    return g_system_height;
+}
+
+JNIEXPORT void JNICALL
+Java_io_swipelab_ux_KeyboardBridge_nSetTracking(JNIEnv *env, jclass cls, jint v) {
+    g_is_tracking = v;
+}
+
+JNIEXPORT void JNICALL
+Java_io_swipelab_ux_KeyboardBridge_nSetAnim(JNIEnv *env, jclass cls, jdouble target, jdouble duration) {
+    g_anim_target = target;
+    g_anim_duration = duration;
+    g_anim_generation++;
+}

android/src/main/kotlin/io/swipelab/ux/KeyboardBridge.kt

@@ -0,0 +1,14 @@
+package io.swipelab.ux
+
+/// JNI bridge to the C globals that Dart reads via FFI.
+object KeyboardBridge {
+    init {
+        System.loadLibrary("ux_keyboard")
+    }
+
+    @JvmStatic external fun nSetHeight(h: Double)
+    @JvmStatic external fun nSetSystemHeight(h: Double)
+    @JvmStatic external fun nGetSystemHeight(): Double
+    @JvmStatic external fun nSetTracking(v: Int)
+    @JvmStatic external fun nSetAnim(target: Double, duration: Double)
+}

android/src/main/kotlin/io/swipelab/ux/KeyboardPlugin.kt

@@ -0,0 +1,116 @@
+package io.swipelab.ux
+
+import android.app.Activity
+import android.graphics.Insets
+import android.os.Build
+import android.view.WindowInsets
+import android.view.WindowInsetsAnimation
+import io.flutter.embedding.engine.plugins.FlutterPlugin
+import io.flutter.embedding.engine.plugins.activity.ActivityAware
+import io.flutter.embedding.engine.plugins.activity.ActivityPluginBinding
+import io.flutter.plugin.common.MethodCall
+import io.flutter.plugin.common.MethodChannel
+
+class KeyboardPlugin : FlutterPlugin, MethodChannel.MethodCallHandler, ActivityAware {
+    private var methodChannel: MethodChannel? = null
+    private var activity: Activity? = null
+
+    override fun onAttachedToEngine(binding: FlutterPlugin.FlutterPluginBinding) {
+        methodChannel = MethodChannel(binding.binaryMessenger, "ux/keyboard").also {
+            it.setMethodCallHandler(this)
+        }
+    }
+
+    override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {
+        methodChannel?.setMethodCallHandler(null)
+        methodChannel = null
+    }
+
+    override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
+        when (call.method) {
+            "enableInteractiveDismiss" -> result.success(null)
+            "disableInteractiveDismiss" -> result.success(null)
+            else -> result.notImplemented()
+        }
+    }
+
+    override fun onAttachedToActivity(binding: ActivityPluginBinding) {
+        activity = binding.activity
+        setupInsetsCallback()
+    }
+
+    override fun onDetachedFromActivity() {
+        activity = null
+    }
+
+    override fun onReattachedToActivityForConfigChanges(binding: ActivityPluginBinding) {
+        activity = binding.activity
+        setupInsetsCallback()
+    }
+
+    override fun onDetachedFromActivityForConfigChanges() {
+        activity = null
+    }
+
+    private fun setupInsetsCallback() {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.R) return
+        val view = activity?.window?.decorView ?: return
+
+        // Catch inset changes that don't trigger animations (e.g., emoji keyboard resize)
+        view.viewTreeObserver.addOnGlobalLayoutListener {
+            val insets = view.rootWindowInsets?.getInsets(WindowInsets.Type.ime()) ?: Insets.NONE
+            val density = view.resources.displayMetrics.density
+            val height = insets.bottom.toDouble() / density
+
+            if (height != KeyboardBridge.nGetSystemHeight()) {
+                KeyboardBridge.nSetSystemHeight(height)
+                KeyboardBridge.nSetHeight(height)
+            }
+        }
+
+        view.setWindowInsetsAnimationCallback(object : WindowInsetsAnimation.Callback(DISPATCH_MODE_STOP) {
+            override fun onPrepare(animation: WindowInsetsAnimation) {}
+
+            override fun onStart(
+                animation: WindowInsetsAnimation,
+                bounds: WindowInsetsAnimation.Bounds
+            ): WindowInsetsAnimation.Bounds {
+                val insets = view.rootWindowInsets?.getInsets(WindowInsets.Type.ime()) ?: Insets.NONE
+                val density = view.resources.displayMetrics.density
+                val targetHeight = insets.bottom.toDouble() / density
+
+                KeyboardBridge.nSetSystemHeight(targetHeight)
+
+                val duration = animation.durationMillis / 1000.0
+                KeyboardBridge.nSetAnim(targetHeight, duration)
+
+                return bounds
+            }
+
+            override fun onProgress(
+                insets: WindowInsets,
+                runningAnimations: MutableList<WindowInsetsAnimation>
+            ): WindowInsets {
+                val imeInsets = insets.getInsets(WindowInsets.Type.ime())
+                val density = view.resources.displayMetrics.density
+                val height = imeInsets.bottom.toDouble() / density
+
+                KeyboardBridge.nSetHeight(height)
+
+                return insets
+            }
+
+            override fun onEnd(animation: WindowInsetsAnimation) {
+                val insets = view.rootWindowInsets?.getInsets(WindowInsets.Type.ime()) ?: Insets.NONE
+                val density = view.resources.displayMetrics.density
+                val height = insets.bottom.toDouble() / density
+
+                KeyboardBridge.nSetHeight(height)
+
+                if (height <= 0) {
+                    KeyboardBridge.nSetSystemHeight(0.0)
+                }
+            }
+        })
+    }
+}

example/lib/main.dart

@@ -1,68 +1,102 @@
 import 'package:flutter/material.dart';
-import 'dart:async';
-
-import 'package:flutter/services.dart';
 import 'package:ux/ux.dart';
 
-void main() => runApp(MyApp());
+void main() => runApp(MaterialApp(home: KeyboardExample()));
 
-class MyApp extends StatefulWidget {
+class KeyboardExample extends StatefulWidget {
   @override
-  _MyAppState createState() => _MyAppState();
+  State<KeyboardExample> createState() => _KeyboardExampleState();
 }
 
-class _MyAppState extends State<MyApp> {
+class _KeyboardExampleState extends State<KeyboardExample> {
-  String _platformVersion = 'Unknown';
+  final _keyboard = UxKeyboard.instance;
+  final _focusNode = FocusNode();
 
   @override
   void initState() {
     super.initState();
-    initPlatformState();
+    _keyboard.addListener(_onKeyboard);
-  }
+    _keyboard.enableInteractiveDismiss(trackingInset: 56);
-
-  // Platform messages are asynchronous, so we initialize in an async method.
-  Future<void> initPlatformState() async {
-    String platformVersion;
-    // Platform messages may fail, so we use a try/catch PlatformException.
-    try {
-      platformVersion = await UX.platformVersion;
-    } on PlatformException {
-      platformVersion = 'Failed to get platform version.';
-    }
-
-    if (!mounted) return;
-
-    setState(() {
-      _platformVersion = platformVersion;
-    });
   }
 
+  @override
+  void dispose() {
+    _keyboard.removeListener(_onKeyboard);
+    _keyboard.disableInteractiveDismiss();
+    _focusNode.dispose();
+    super.dispose();
+  }
+
+  void _onKeyboard() => setState(() {});
+
   @override
   Widget build(BuildContext context) {
-    return MaterialApp(
+    final bottomInset = _keyboard.height;
-      routes: {
+    final safeArea = MediaQuery.paddingOf(context).bottom;
-        '/': (context) => Scaffold(
+    final bottom = bottomInset > 0 ? bottomInset : safeArea;
-              appBar: AppBar(
+
-                title: const Text('Plugin example app'),
+    return Scaffold(
-              ),
+      resizeToAvoidBottomInset: false,
-              body: Builder(
+      appBar: AppBar(title: Text('UxKeyboard')),
-                builder: (context) => ListView(
+      body: Column(
-                  padding: EdgeInsets.only(top: 48),
+        children: [
-                  children: [
+          Expanded(
-                    ListTile(title: Text('Running on: $_platformVersion\n')),
+            child: ListView.builder(
-                    ListTile(
+              reverse: true,
-                      title: Text('Show a simple note'),
+              padding: EdgeInsets.only(bottom: 60 + bottom, top: 16),
-                      //onTap: () => context.showText('This is a simple note'),
+              itemCount: 30,
+              itemBuilder: (context, i) => Padding(
+                padding: EdgeInsets.symmetric(horizontal: 16, vertical: 4),
+                child: Align(
+                  alignment: i % 3 == 0 ? Alignment.centerRight : Alignment.centerLeft,
+                  child: Container(
+                    padding: EdgeInsets.symmetric(horizontal: 14, vertical: 10),
+                    decoration: BoxDecoration(
+                      color: i % 3 == 0 ? Colors.blue[100] : Colors.grey[200],
+                      borderRadius: BorderRadius.circular(16),
                     ),
-                    ListTile(
+                    child: Text('Message ${30 - i}'),
-                      title: Text('Show modal note'),
+                  ),
-                      //onTap: () => context.showText('This is a modal note', backdropBlur: 6, modal: true),
-                    )
-                  ],
                 ),
               ),
-            )
+            ),
-      },
+          ),
+          Container(
+            padding: EdgeInsets.only(
+              left: 12,
+              right: 12,
+              top: 8,
+              bottom: 8 + bottom,
+            ),
+            decoration: BoxDecoration(
+              color: Colors.white,
+              border: Border(top: BorderSide(color: Colors.grey[300]!)),
+            ),
+            child: Row(
+              children: [
+                Expanded(
+                  child: TextField(
+                    focusNode: _focusNode,
+                    decoration: InputDecoration(
+                      hintText: 'Type a message...',
+                      border: OutlineInputBorder(
+                        borderRadius: BorderRadius.circular(24),
+                      ),
+                      contentPadding: EdgeInsets.symmetric(horizontal: 16, vertical: 10),
+                      isDense: true,
+                    ),
+                  ),
+                ),
+                SizedBox(width: 8),
+                IconButton(
+                  icon: Icon(Icons.send, color: Colors.blue),
+                  onPressed: () {},
+                ),
+              ],
+            ),
+          ),
+        ],
+      ),
     );
   }
 }

ios/Classes/UxPlugin.h

@@ -1,4 +0,0 @@
-#import <Flutter/Flutter.h>
-
-@interface UxPlugin : NSObject<FlutterPlugin>
-@end

ios/Classes/UxPlugin.m

@@ -1,20 +0,0 @@
-#import "UxPlugin.h"
-
-@implementation UxPlugin
-+ (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar>*)registrar {
-  FlutterMethodChannel* channel = [FlutterMethodChannel
-      methodChannelWithName:@"ux"
-            binaryMessenger:[registrar messenger]];
-  UxPlugin* instance = [[UxPlugin alloc] init];
-  [registrar addMethodCallDelegate:instance channel:channel];
-}
-
-- (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
-  if ([@"getPlatformVersion" isEqualToString:call.method]) {
-    result([@"iOS " stringByAppendingString:[[UIDevice currentDevice] systemVersion]]);
-  } else {
-    result(FlutterMethodNotImplemented);
-  }
-}
-
-@end

ios/ux.podspec

@@ -1,21 +1,13 @@
-#
-# To learn more about a Podspec see http://guides.cocoapods.org/syntax/podspec.html
-#
 Pod::Spec.new do |s|
   s.name             = 'ux'
-  s.version          = '0.0.1'
+  s.version          = '0.2.0'
-  s.summary          = 'A new flutter plugin project.'
+  s.summary          = 'UX Kit – Flutter plugin with keyboard tracking and interactive dismiss.'
-  s.description      = <<-DESC
+  s.homepage         = 'https://swipelab.co/ux.html'
-A new flutter plugin project.
-                       DESC
-  s.homepage         = 'http://example.com'
   s.license          = { :file => '../LICENSE' }
-  s.author           = { 'Your Company' => 'email@example.com' }
+  s.author           = { 'Swipelab' => 'hello@swipelab.co' }
   s.source           = { :path => '.' }
-  s.source_files = 'Classes/**/*'
+  s.source_files     = 'Classes/**/*.swift'
-  s.public_header_files = 'Classes/**/*.h'
   s.dependency 'Flutter'
-
+  s.ios.deployment_target = '13.0'
-  s.ios.deployment_target = '8.0'
+  s.swift_version = '5.0'
 end
-

lib/src/keyboard.dart

@@ -5,11 +5,10 @@ import 'package:flutter/animation.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/scheduler.dart';
 
-final bool _isIOS = Platform.isIOS;
-
 DynamicLibrary? _initLib() {
-  if (!_isIOS) return null;
+  if (Platform.isIOS) return DynamicLibrary.process();
-  return DynamicLibrary.process();
+  if (Platform.isAndroid) return DynamicLibrary.open('libux_keyboard.so');
+  return null;
 }
 
 final DynamicLibrary? _lib = _initLib();
@@ -90,7 +89,7 @@ class _SampledCurve extends Curve {
 
 class UxKeyboard with ChangeNotifier {
   UxKeyboard._() {
-    if (!_isIOS) return;
+    if (_lib == null) return;
     SchedulerBinding.instance.addPersistentFrameCallback(_onFrame);
   }
 
@@ -116,18 +115,22 @@ class UxKeyboard with ChangeNotifier {
 
     final ts = timestamp.inMicroseconds / Duration.microsecondsPerSecond;
 
-    // Detect new keyboard animation from native
+    // On iOS, replay the animation in Dart with a head start (native only
-    final gen = _uxAnimGen?.call() ?? 0;
+    // gives start/end via notification). On Android, WindowInsetsAnimation
-    if (gen != _lastAnimGen) {
+    // pushes per-frame values directly — no replay needed.
-      _lastAnimGen = gen;
+    if (Platform.isIOS) {
-      final target = _uxAnimTarget?.call() ?? 0;
+      final gen = _uxAnimGen?.call() ?? 0;
-      final duration = _uxAnimDuration?.call() ?? 0;
+      if (gen != _lastAnimGen) {
-      if (duration > 0) {
+        _lastAnimGen = gen;
-        _animFrom = _height;
+        final target = _uxAnimTarget?.call() ?? 0;
-        _animTo = target;
+        final duration = _uxAnimDuration?.call() ?? 0;
-        _animDuration = duration - 0.01; // finish 10ms ahead of native
+        if (duration > 0) {
-        _animStartTime = ts - 0.016; // compensate 2-frame pipeline delay
+          _animFrom = _height;
-        _isAnimating = true;
+          _animTo = target;
+          _animDuration = duration - 0.01; // finish 10ms ahead of native
+          _animStartTime = ts - 0.016; // compensate 2-frame pipeline delay
+          _isAnimating = true;
+        }
       }
     }
 
@@ -155,7 +158,8 @@ class UxKeyboard with ChangeNotifier {
       notifyListeners();
     }
 
-    if (_isAnimating) {
+    // Keep scheduling frames while animating or keyboard is active
+    if (_isAnimating || (!Platform.isIOS && (h > 0 || _height > 0))) {
       SchedulerBinding.instance.scheduleFrame();
     }
   }

lib/ux.dart

@@ -3,15 +3,4 @@ library ux;
 export 'src/bend_box.dart';
 export 'src/json_extension.dart';
 export 'src/bezier.dart';
-
+export 'src/keyboard.dart';
-import 'dart:async';
-import 'package:flutter/services.dart';
-
-class UX {
-  static const MethodChannel _channel = const MethodChannel('ux');
-
-  static Future<String> get platformVersion async {
-    final String version = await _channel.invokeMethod('getPlatformVersion');
-    return version;
-  }
-}

pubspec.yaml

@@ -16,5 +16,9 @@ dev_dependencies:
 
 flutter:
   plugin:
-    androidPackage: io.swipelab.ux
+    platforms:
-    pluginClass: UxPlugin
+      ios:
+        pluginClass: KeyboardPlugin
+      android:
+        package: io.swipelab.ux
+        pluginClass: KeyboardPlugin