Flutter 跑马灯 消息滚动

效果图

使用示例：

new YYMarquee(
  new Text("YYMarqueeYYMarqueeYYMarqueeYYMarqueeYYMarqueeYYMarqueeYYMarqueeYYMarqueeYYMarqueeYYMarquee"), 
  200.0,
  new Duration(seconds: 2),
  230.0
)

具体代码：

import 'package:flutter/material.dart';
import 'dart:async';  //Timer

class YYMarquee extends StatefulWidget {
  Widget child;  // 轮播的内容
  Duration duration;  // 轮播时间
  double stepOffset;  // 偏移量
  double paddingLeft;  // 内容之间的间距

  YYMarquee(this.child, this.paddingLeft, this.duration, this.stepOffset);

  _YYMarqueeState createState() => _YYMarqueeState();
}


class _YYMarqueeState extends State {
  ScrollController _controller;  // 执行动画的controller
  Timer _timer;  // 定时器timer
  double _offset = 0.0;  // 执行动画的偏移量

  @override
  void initState() {
    super.initState();

    _controller = ScrollController(initialScrollOffset: _offset);
    _timer = Timer.periodic(widget.duration, (timer) {
      double newOffset = _controller.offset + widget.stepOffset;
      if (newOffset != _offset) {
        _offset = newOffset;
        _controller.animateTo(
            _offset,
            duration: widget.duration, curve: Curves.linear);  // 线性曲线动画 
      }
    });
  }

  @override
  void dispose() {
    _timer.cancel();
    _controller.dispose();
    super.dispose();
  }

  Widget _child() {
    return new Row(
        children: _children()
    );
  }

  // 子视图
  List _children() {
    List items = [];
    for (var i = 0; i<=2; i++) {
      Container item = new Container(
        margin: new EdgeInsets.only(right: i != 0 ? 0.0 : widget.paddingLeft),
        child: i != 0 ? null : widget.child,
      );
      items.add(item);
    }
    return items;
  }

  @override
  Widget build(BuildContext context) {
    return ListView.builder(
      scrollDirection: Axis.horizontal,  // 横向滚动
      controller: _controller,  // 滚动的controller
      itemBuilder: (context, index) {
        return _child();
      },
    );
  }
}