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lib/flutterlib/flutter_count_controller.dart

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+import 'package:flutter/material.dart';
+
+class FlutterCountController extends StatefulWidget {
+  const FlutterCountController({
+    Key? key,
+    required this.decrementIconBuilder,
+    required this.incrementIconBuilder,
+    required this.countBuilder,
+    required this.count,
+    required this.updateCount,
+    this.stepSize = 1,
+    this.minimum,
+    this.maximum,
+    this.contentPadding = const EdgeInsets.symmetric(horizontal: 25.0),
+  }) : super(key: key);
+
+  final Widget Function(bool enabled) decrementIconBuilder;
+  final Widget Function(bool enabled) incrementIconBuilder;
+  final Widget Function(int count) countBuilder;
+  final int count;
+  final Function(int) updateCount;
+  final int stepSize;
+  final int? minimum;
+  final int? maximum;
+  final EdgeInsetsGeometry contentPadding;
+
+  @override
+  _FlutterCountControllerState createState() =>
+      _FlutterCountControllerState();
+}
+
+class _FlutterCountControllerState
+    extends State<FlutterCountController> {
+  int get count => widget.count;
+  int? get minimum => widget.minimum;
+  int? get maximum => widget.maximum;
+  int get stepSize => widget.stepSize;
+
+  bool get canDecrement => minimum == null || count - stepSize >= minimum!;
+  bool get canIncrement => maximum == null || count + stepSize <= maximum!;
+
+  void _decrementCounter() {
+    if (canDecrement) {
+      setState(() => widget.updateCount(count - stepSize));
+    }
+  }
+
+  void _incrementCounter() {
+    if (canIncrement) {
+      setState(() => widget.updateCount(count + stepSize));
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) => Padding(
+        padding: widget.contentPadding,
+        child: Row(
+          mainAxisAlignment: MainAxisAlignment.spaceBetween,
+          children: [
+            InkWell(
+              onTap: _decrementCounter,
+              child: widget.decrementIconBuilder(canDecrement),
+            ),
+            widget.countBuilder(count),
+            InkWell(
+              onTap: _incrementCounter,
+              child: widget.incrementIconBuilder(canIncrement),
+            ),
+          ],
+        ),
+      );
+}