flutter_bouncy 0.0.14

Scrolling with bouncy and natural item movement

example/lib/main.dart

import 'dart:async';
import 'dart:math';

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:flutter/physics.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter_bouncy/main.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage>
    with SingleTickerProviderStateMixin {
  int _counter = 0;
  final tween = Tween<double>(begin: 0.0, end: 0.0);
  ScrollController scrollController;
  Offset globalPosition;
  double lastPixels;

  @override
  void initState() {
    scrollController = ScrollController();
    super.initState();
  }

  void _incrementCounter() {
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    final children = [
      _buildChatMessage(true),
      _buildChatMessage(false),
      _buildChatMessage(true),
      _buildChatMessage(true),
      _buildChatMessage(true),
      _buildChatMessage(false),
      _buildChatMessage(false),
      _buildChatMessage(true),
      _buildChatMessage(false),
      _buildChatMessage(true),
      _buildChatMessage(true),
      _buildChatMessage(false),
      _buildChatMessage(false),
      _buildChatMessage(true),
      _buildChatMessage(true),
      _buildChatMessage(true),
      _buildChatMessage(false),
      _buildChatMessage(true),
      _buildChatMessage(true),
      _buildChatMessage(true),
      _buildChatMessage(false),
      _buildChatMessage(false),
      _buildChatMessage(true),
      _buildChatMessage(false),
      _buildChatMessage(true),
      _buildChatMessage(true),
      _buildChatMessage(false),
      _buildChatMessage(true),
      _buildChatMessage(true),
      _buildChatMessage(false),
      _buildChatMessage(true),
      _buildChatMessage(true),
    ];
    return Scaffold(
      body: SafeArea(
        child: NotificationListener<ScrollNotification>(
          onNotification: (notification) {
            // print('Pixels: ${notification.metrics.pixels}');
            if (notification is ScrollUpdateNotification) {
              if (notification.dragDetails != null) {
                setState(() {
                  globalPosition = notification.dragDetails.globalPosition;
                });
                // tween.begin = scrollDelta;
                // tween.end = notification.scrollDelta;

                // if (controller.isCompleted) {
                //   controller.reset();
                // }

                // if (!controller.isAnimating) {
                //   controller.forward();
                // }
              }
            }

            if (notification is ScrollEndNotification) {
              // controller.reset();

            }
            return false;
          },
          child: Padding(
            padding: EdgeInsets.symmetric(horizontal: 10),
            child: AnimatedBouncyList(
              reverse: true,
              itemBuilder: (ctx, i, anim) {
                return children[i];
              },
              initialItemCount: children.length,
            ),
          ),
        ),
      ),
    );
  }

  Widget _buildChatMessage(bool isSender) {
    return Padding(
      padding: EdgeInsets.symmetric(vertical: 10),
      child: Align(
        alignment: isSender ? Alignment.centerRight : Alignment.centerLeft,
        child: FractionallySizedBox(
          widthFactor: 0.8,
          child: Container(
            height: 25,
            decoration: BoxDecoration(
              color: isSender ? Colors.blue : Colors.grey.withOpacity(0.4),
              borderRadius: BorderRadius.circular(10),
            ),
          ),
        ),
      ),
    );
  }
}

class Spring {
  final Function handler;

  SpringSimulation _simulation;
  double current = 0.0;
  double dt = 0;

  Spring(this.handler) {
    final timer = Timer.periodic(
      Duration(milliseconds: 1),
      (_) {
        if (_simulation != null) {
          current = _simulation.x(dt / 100);
          // print('Current: $current');
        }
        if (dt % 1000 == 0) {
          // print('DT: $dt');
        }
        dt++;
        handler();
      },
    );
  }

  void setTarget(double target) {
    _simulation = SpringSimulation(
      _getSpringDescription(),
      current,
      target,
      0.01,
    );

    dt = 0;
  }

  SpringDescription _getSpringDescription() {
    return const SpringDescription(
      mass: 20.0,
      stiffness: 0.6,
      damping: 0.4,
    );
  }
}