效果
引言
在Flutter应用中实现物理动画效果,可以大大提升用户体验。本文将详细介绍如何在Flutter中创建一个模拟物理碰撞的动画小球界面,主要代码实现基于集成sensors_plus
插件来获取设备的加速度传感器数据。
准备工作
在开始之前,请确保在pubspec.yaml
文件中添加sensors_plus
插件:
dependencies:flutter:sdk: fluttersensors_plus: 4.0.2
然后运行flutter pub get
命令来获取依赖。
代码结构
我们将实现一个名为PhysicsBallWidget
的自定义小部件,主要包含以下几部分:
- Ball类:表示每个球的基本信息。
- BadgeBallConfig类:管理每个球的状态和行为。
- PhysicsBallWidget类:主部件,包含球的逻辑和动画。
- BallItemWidget类:具体显示每个球的小部件。
- BallListPage类:测试页面,展示物理球动画效果。
Ball类
首先定义Ball
类,用于表示每个球的基本信息,例如名称:
class Ball {final String name;Ball({required this.name});
}
BadgeBallConfig类
BadgeBallConfig
类用于管理每个球的状态和行为,包括加速度、速度、位置等信息:
class BadgeBallConfig {final Acceleration _acceleration = Acceleration(0, 0);final double time = 0.02;late Function(Offset) collusionCallback;Size size = const Size(100, 100);Speed _speed = Speed(0, 0);late Offset _position;late String name;double oppositeAccelerationCoefficient = 0.7;void setPosition(Offset offset) {_position = offset;}void setInitSpeed(Speed speed) {_speed = speed;}void setOppositeSpeed(bool x, bool y) {if (x) {_speed.x = -_speed.x * oppositeAccelerationCoefficient;if (_speed.x.abs() < 5) _speed.x = 0;}if (y) {_speed.y = -_speed.y * oppositeAccelerationCoefficient;if (_speed.y.abs() < 5) _speed.y = 0;}}void setAcceleration(double x, double y) {_acceleration.x = x * oppositeAccelerationCoefficient;_acceleration.y = y * oppositeAccelerationCoefficient;}Speed getCurrentSpeed() => _speed;Offset getCurrentCenter() => Offset(_position.dx + size.width / 2,_position.dy + size.height / 2,);Offset getCurrentPosition() => _position;void inertiaStart(double x, double y) {if (x.abs() > _acceleration.x.abs()) _speed.x += x;if (y.abs() > _acceleration.y.abs()) _speed.y += y;}void afterCollusion(Offset offset, Speed speed) {_speed = Speed(speed.x * oppositeAccelerationCoefficient,speed.y * oppositeAccelerationCoefficient,);_position = offset;collusionCallback(offset);}Offset getOffset() {var offsetX = (_acceleration.x.abs() < 5 && _speed.x.abs() < 3) ? 0.0 : _speed.x * time + (_acceleration.x * time * time) / 2;var offsetY = (_acceleration.y.abs() < 5 && _speed.y.abs() < 6) ? 0.0 : _speed.y * time + (_acceleration.y * time * time) / 2;_position = Offset(_position.dx + offsetX, _position.dy + offsetY);_speed = Speed(_speed.x + _acceleration.x * time,_speed.y + _acceleration.y * time,);return _position;}
}class Speed {double x;double y;Speed(this.x, this.y);
}class Acceleration {double x;double y;Acceleration(this.x, this.y);
}
PhysicsBallWidget类
PhysicsBallWidget
类是主部件,负责处理球的逻辑和动画:
import 'dart:math';
import 'package:flutter/material.dart';
import 'package:flutter/scheduler.dart';
import 'package:flutter_screenutil/flutter_screenutil.dart';
import 'package:flutter_xy/application.dart';
import 'package:flutter_xy/xydemo/ball/ball_model.dart';
import 'package:sensors_plus/sensors_plus.dart';
//https://github.com/yixiaolunhui/flutter_xy
class PhysicsBallWidget extends StatefulWidget {final List<Ball> ballList;final double height;final double width;const PhysicsBallWidget({required this.ballList,required this.width,required this.height,Key? key,}) : super(key: key);State<StatefulWidget> createState() => _PhysicsBallState();
}class _PhysicsBallState extends State<PhysicsBallWidget> {List<Widget> badgeBallList = [];List<ValueKey<BadgeBallConfig>> keyList = [];late Size ballSize;void initState() {super.initState();fillKeyList();WidgetsBinding.instance.addPostFrameCallback((timeStamp) {App.get().addPersistentFrameCallback(travelHitMap);});}void dispose() {App.get().removePersistentFrameCallback(travelHitMap);super.dispose();}Widget build(BuildContext context) {fillWidgetList();return Stack(children: badgeBallList,);}void fillKeyList() {var badgeSize = (widget.width - 20) / 6;badgeSize = (badgeSize >= 84.0 || badgeSize <= 0.0 || !badgeSize.isFinite)? 84.0: badgeSize;var maxCount = ((widget.height - badgeSize) ~/ badgeSize) *(widget.width ~/ badgeSize);if (widget.ballList.length >= maxCount) {badgeSize = 50.0;}ballSize = Size(badgeSize, badgeSize);var initOffsetX = 0.0;var initOffsetY = widget.height - badgeSize;for (var element in widget.ballList) {keyList.add(ValueKey<BadgeBallConfig>(BadgeBallConfig()..size = ballSize..name = element.name..setPosition(Offset(initOffsetX, initOffsetY)),));initOffsetX += badgeSize;if (initOffsetX + badgeSize > widget.width - 20) {initOffsetX = 0;initOffsetY -= badgeSize;}}}void fillWidgetList() {badgeBallList.clear();for (var e in keyList) {badgeBallList.add(BallItemWidget(key: e,limitWidth: widget.width,limitHeight: widget.height,onTap: () {},),);}}void travelHitMap(Duration timeStamp) {for (var i = 0; i < keyList.length - 1; i++) {for (var j = i + 1; j < keyList.length; j++) {hit(keyList[i].value, keyList[j].value);}}}void hit(BadgeBallConfig a, BadgeBallConfig b) {final distance = a.size.height / 2 + b.size.height / 2;final w = b.getCurrentCenter().dx - a.getCurrentCenter().dx;final h = b.getCurrentCenter().dy - a.getCurrentCenter().dy;if (sqrt(w * w + h * h) <= distance) {var aOriginSpeed = a.getCurrentSpeed();var bOriginSpeed = b.getCurrentSpeed();var aOffset = a.getCurrentPosition();var angle = atan2(h, w);var sinNum = sin(angle);var cosNum = cos(angle);var aCenter = [0.0, 0.0];var bCenter = coordinateTranslate(w, h, sinNum, cosNum, true);var aSpeed = coordinateTranslate(aOriginSpeed.x, aOriginSpeed.y, sinNum, cosNum, true);var bSpeed = coordinateTranslate(bOriginSpeed.x, bOriginSpeed.y, sinNum, cosNum, true);var vxTotal = aSpeed[0] - bSpeed[0];aSpeed[0] = (2 * 10 * bSpeed[0]) / 20;bSpeed[0] = vxTotal + aSpeed[0];var overlap = distance - (aCenter[0] - bCenter[0]).abs();aCenter[0] -= overlap;bCenter[0] += overlap;var aRotatePos =coordinateTranslate(aCenter[0], aCenter[1], sinNum, cosNum, false);var bRotatePos =coordinateTranslate(bCenter[0], bCenter[1], sinNum, cosNum, false);var bOffsetX = aOffset.dx + bRotatePos[0];var bOffsetY = aOffset.dy + bRotatePos[1];var aOffsetX = aOffset.dx + aRotatePos[0];var aOffsetY = aOffset.dy + aRotatePos[1];var aSpeedF =coordinateTranslate(aSpeed[0], aSpeed[1], sinNum, cosNum, false);var bSpeedF =coordinateTranslate(bSpeed[0], bSpeed[1], sinNum, cosNum, false);a.afterCollusion(Offset(aOffsetX, aOffsetY), Speed(aSpeedF[0], aSpeedF[1]));b.afterCollusion(Offset(bOffsetX, bOffsetY), Speed(bSpeedF[0], bSpeedF[1]));}}List<double> coordinateTranslate(double x, double y, double sin, double cos, bool reverse) {return reverse? [x * cos + y * sin, y * cos - x * sin]: [x * cos - y * sin, y * cos + x * sin];}
}
BallItemWidget类
BallItemWidget
类用于具体显示每个球,并处理其动画和事件:
import 'dart:async';
import 'dart:math';
import 'package:flutter/material.dart';
import 'package:flutter/scheduler.dart';
import 'package:flutter_screenutil/flutter_screenutil.dart';
import 'package:flutter_xy/application.dart';
import 'package:flutter_xy/xydemo/ball/ball_model.dart';
import 'package:sensors_plus/sensors_plus.dart';class BallItemWidget extends StatefulWidget {final double limitWidth;final double limitHeight;final Function onTap;const BallItemWidget({required this.limitWidth,required this.limitHeight,required this.onTap,Key? key,}) : super(key: key);State<StatefulWidget> createState() => BallItemState();
}class BallItemState extends State<BallItemWidget> {final List<StreamSubscription<dynamic>> _streamSubscriptions = [];late BadgeBallConfig config;Duration sensorInterval = SensorInterval.normalInterval;var color = Color.fromARGB(255,Random().nextInt(256),Random().nextInt(256),Random().nextInt(256),);Timer? timer;double x = 0;double y = 0;double limitY = 0;double limitX = 0;void initState() {super.initState();initData();_streamSubscriptions.add(accelerometerEvents.listen((AccelerometerEvent event) {config.setAcceleration(-double.parse(event.x.toStringAsFixed(1)) * 50,double.parse(event.y.toStringAsFixed(1)) * 50,);},),);_streamSubscriptions.add(userAccelerometerEvents.listen((UserAccelerometerEvent event) {config.inertiaStart(double.parse(event.x.toStringAsFixed(1)) * 50,-double.parse(event.y.toStringAsFixed(1)) * 20,);},),);timer = Timer.periodic(const Duration(milliseconds: 20), (timer) {if (!SchedulerBinding.instance.hasScheduledFrame) {SchedulerBinding.instance.scheduleFrame();}});WidgetsBinding.instance.addPostFrameCallback((timeStamp) {App.get().addPersistentFrameCallback(updatePosition);});}void dispose() {super.dispose();for (var subscription in _streamSubscriptions) {subscription.cancel();}App.get().removePersistentFrameCallback(updatePosition);timer?.cancel();timer = null;}Widget build(BuildContext context) {return AnimatedPositioned(left: x,top: y,duration: const Duration(milliseconds: 16),child: GestureDetector(onTap: () {widget.onTap.call();},child: Container(width: config.size.width,alignment: Alignment.center,height: config.size.height,decoration: BoxDecoration(shape: BoxShape.circle,border: Border.all(color: color, width: 2.w),),child: Text(config.name,style: TextStyle(fontSize: 16.w, color: Colors.red),),),),);}void initData() {limitX = widget.limitWidth;limitY = widget.limitHeight;config = (widget.key as ValueKey<BadgeBallConfig>).value;config.collusionCallback = (offset) {setState(() {x = offset.dx;y = offset.dy;config.setPosition(offset);});};x = config.getCurrentPosition().dx;y = config.getCurrentPosition().dy;}void updatePosition(Duration timeStamp) {setState(() {var tempX = config.getOffset().dx;var tempY = config.getOffset().dy;if (tempX < 0) {tempX = 0;config.setOppositeSpeed(true, false);}if (tempX > limitX - config.size.width) {tempX = limitX - config.size.width;config.setOppositeSpeed(true, false);}if (tempY < 0) {tempY = 0;config.setOppositeSpeed(false, true);}if (tempY > limitY - config.size.height) {tempY = limitY - config.size.height;config.setOppositeSpeed(false, true);}x = tempX;y = tempY;config.setPosition(Offset(x, y));});}
}
BallListPage类
BallListPage
类是测试页面,用于展示物理球动画效果:
import 'package:flutter/material.dart';
import 'package:flutter_xy/xydemo/ball/ball_model.dart';
import 'package:flutter_xy/xydemo/ball/ball_widget.dart';class BallListPage extends StatefulWidget {const BallListPage({super.key});State<BallListPage> createState() => _BallListPageState();
}class _BallListPageState extends State<BallListPage> {final List<Ball> badgeList = [Ball(name: '北京'),Ball(name: '上海'),Ball(name: '天津'),Ball(name: '徐州'),Ball(name: '南京'),Ball(name: '苏州'),Ball(name: '杭州'),Ball(name: '合肥'),Ball(name: '武汉'),Ball(name: '常州'),Ball(name: '香港'),Ball(name: '澳门'),Ball(name: '新疆'),Ball(name: '成都'),Ball(name: '宿迁'),];Widget build(BuildContext context) {return Scaffold(body: Stack(children: [PhysicsBallWidget(ballList: badgeList,height: MediaQuery.of(context).size.height,width: MediaQuery.of(context).size.width,),],),);}
}
结论
通过这篇博客,我们展示了如何在Flutter中实现一个物理球动画效果,并且集成了sensors_plus
插件来获取设备的加速度传感器数据。希望这篇博客能对您在Flutter开发中实现类似效果有所帮助。
详情见:github.com/yixiaolunhui/flutter_xy