From a378c199ec74f793f2bf8294d68fadad40576de2 Mon Sep 17 00:00:00 2001
From: NiklasLehnfeld <niklas@lehnfeld.net>
Date: Tue, 28 Jul 2020 15:14:28 +0200
Subject: [PATCH 1/2] added widget reacting on keyboard visibility changes

---
 lib/keyboard_visibility_builder.dart | 37 ++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100644 lib/keyboard_visibility_builder.dart

diff --git a/lib/keyboard_visibility_builder.dart b/lib/keyboard_visibility_builder.dart
new file mode 100644
index 0000000..8756483
--- /dev/null
+++ b/lib/keyboard_visibility_builder.dart
@@ -0,0 +1,37 @@
+import 'package:flutter/material.dart';
+import 'package:keyboard_visibility/keyboard_visibility.dart';
+
+/// A Widget reacting on keyboard visibility changes using [KeyboardVisibilityNotification]  and triggering a rebuild
+class KeyboardVisibilityBuilder extends StatefulWidget {
+
+  /// Builder used to create child widget
+  final Widget Function(BuildContext, bool) builder;
+
+  /// Constructs a new [KeyboardVisibilityBuilder]
+  KeyboardVisibilityBuilder({this.builder});
+
+  @override
+  _KeyboardVisibilityBuilderState createState() => _KeyboardVisibilityBuilderState();
+}
+
+class _KeyboardVisibilityBuilderState extends State<KeyboardVisibilityBuilder> {
+
+  /// Holds the current visibility state of the Keyboard
+  bool _keyboardVisible = false;
+
+  @override
+  void initState() { 
+
+    /// Register the listener for updating the [_keyboardVisible] variable and triggering the rebuild
+    KeyboardVisibilityNotification().addNewListener(
+      onChange: (visible) => setState(() => _keyboardVisible = visible)
+    );
+    super.initState();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    /// Building child using the [builder] parsed to the constructor
+    return widget.builder(context, _keyboardVisible);
+  }
+}
\ No newline at end of file

From dded469cfd98c69b5f9f7b2d851e06b22dd8fec5 Mon Sep 17 00:00:00 2001
From: NiklasLehnfeld <niklas@lehnfeld.net>
Date: Tue, 28 Jul 2020 15:37:00 +0200
Subject: [PATCH 2/2] added unsubscribing of listener when widget disposes

---
 lib/keyboard_visibility_builder.dart | 57 ++++++++++++++++++++++++++--
 1 file changed, 54 insertions(+), 3 deletions(-)

diff --git a/lib/keyboard_visibility_builder.dart b/lib/keyboard_visibility_builder.dart
index 8756483..bb26e98 100644
--- a/lib/keyboard_visibility_builder.dart
+++ b/lib/keyboard_visibility_builder.dart
@@ -7,8 +7,17 @@ class KeyboardVisibilityBuilder extends StatefulWidget {
   /// Builder used to create child widget
   final Widget Function(BuildContext, bool) builder;
 
+  /// Callback for when the current visibility state of the keyboard changes
+  final void Function(bool) onChange;
+
+  /// Callback for when the keyboard gets opened
+  final void Function() onShow;
+
+  /// Callback for when the keyboard gets closed
+  final void Function() onHide;
+
   /// Constructs a new [KeyboardVisibilityBuilder]
-  KeyboardVisibilityBuilder({this.builder});
+  KeyboardVisibilityBuilder({this.builder, this.onChange, this.onHide, this.onShow});
 
   @override
   _KeyboardVisibilityBuilderState createState() => _KeyboardVisibilityBuilderState();
@@ -16,22 +25,64 @@ class KeyboardVisibilityBuilder extends StatefulWidget {
 
 class _KeyboardVisibilityBuilderState extends State<KeyboardVisibilityBuilder> {
 
+  /// Holds the id defined by the notifier for later unsubscribing
+  int _subscribingId;
+
+  /// Holds the notifier which will send the keyboard events 
+  KeyboardVisibilityNotification _notifier;
+
   /// Holds the current visibility state of the Keyboard
   bool _keyboardVisible = false;
 
   @override
   void initState() { 
 
+    _notifier = KeyboardVisibilityNotification();
+
     /// Register the listener for updating the [_keyboardVisible] variable and triggering the rebuild
-    KeyboardVisibilityNotification().addNewListener(
-      onChange: (visible) => setState(() => _keyboardVisible = visible)
+    _subscribingId = _notifier.addNewListener(
+      onChange: (value) => _onVisibilityChanged(value),
+      onHide: () => _onHide(),
+      onShow: () => _onShow(),
     );
     super.initState();
   }
 
+  @override
+  void dispose() {
+    /// Removes the listener when the widget gets disposed
+    _notifier.removeListener(_subscribingId);
+    super.dispose();
+  }
+
   @override
   Widget build(BuildContext context) {
     /// Building child using the [builder] parsed to the constructor
     return widget.builder(context, _keyboardVisible);
   }
+
+  /// Callback which gets called by [_notifier] when the keyboard visibility gets changed
+  void _onVisibilityChanged(bool isVisible) {
+    setState(() {
+      _keyboardVisible = isVisible;
+    });
+    
+    if (widget.onChange != null) {
+      widget.onChange(isVisible);
+    } 
+  }
+
+  /// Callback which gets called by [_notifier] when the keyboard gets dismissed
+  void _onHide() {
+    if (widget.onHide != null) {
+      widget.onHide();
+    }
+  }
+
+  /// Callback which gets called by [_notifier] when the keyboard gets opened
+  void _onShow() {
+    if (widget.onShow != null) {
+      widget.onShow();
+    }
+  }
 }
\ No newline at end of file