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import 'package:flutter/material.dart';

@@ -11,9 +13,12 @@

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class _BouncingBallDemoState extends State<BouncingBallDemo>

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with SingleTickerProviderStateMixin {

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+
              late AnimationController controller;

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@override

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void initState() {

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super.initState();

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+
                controller = AnimationController();

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@override