Flutter 文字上下滚动切换 用于公告消息提示

Posted 2022-07-15 早起的年轻人

效果预览

1 基本使用代码

void main() 
  ///启动根目录
  runApp(MaterialApp(
    home: TestTipsPage(),
  ));


class TestTipsPage extends StatefulWidget 
  @override
  _TestTipsPageState createState() => _TestTipsPageState();


class _TestTipsPageState extends State<TestTipsPage> 
  @override
  void initState() 
    super.initState();
  

  @override
  Widget build(BuildContext context) 
    return Scaffold(
      backgroundColor: Colors.white,
      body: Center(
        child: Container(
          alignment: Alignment.center,
          width: double.infinity,
          height: 24,
          child: buildMarqueeWidget(),
        ),
      ),
    );
  
 

2 核心使用代码

  MarqueeWidget buildMarqueeWidget(List<String> loopList) 
    ///上下轮播 安全提示
    return MarqueeWidget(
      //子Item构建器
      itemBuilder: (BuildContext context, int index) 
        String itemStr = loopList[index];
        //通常可以是一个 Text文本
        return Text(itemStr);
      ,
      //循环的提示消息数量
      count: loopList.length,
    );
  

3 核心实现代码

import 'dart:async';
import 'package:flutter/cupertino.dart';

// 上下滚动的消息轮播
class MarqueeWidget extends StatefulWidget 
  /// 子视图数量
  final int count; 
  ///子视图构建器
  final IndexedWidgetBuilder itemBuilder;
  ///轮播的时间间隔
  final int loopSeconds;

  const MarqueeWidget(
    Key? key,
    required this.count,
    required this.itemBuilder,
    this.loopSeconds = 5,
  ) : super(key: key); 

  @override
  _MarqueeWidgetState createState() => _MarqueeWidgetState();


class _MarqueeWidgetState extends State<MarqueeWidget> 
  late PageController _controller;
  late Timer _timer;

  @override
  void initState() 
    super.initState();
    _controller = PageController();
    _timer = Timer.periodic(Duration(seconds: widget.loopSeconds), (timer) 
      if (_controller.page != null) 
        // 如果当前位于最后一页，则直接跳转到第一页，两者内容相同，跳转时视觉上无感知
        if (_controller.page!.round() >= widget.count) 
          _controller.jumpToPage(0);
        
        _controller.nextPage(
            duration: const Duration(seconds: 1), curve: Curves.linear);
      
    );
  

  @override
  Widget build(BuildContext context) 
    return PageView.builder(
      scrollDirection: Axis.vertical,
      controller: _controller,
      itemBuilder: (buildContext, index) 
        if (index < widget.count) 
          return widget.itemBuilder(buildContext, index);
         else 
          return widget.itemBuilder(buildContext, 0);
        
      ,
      itemCount: widget.count + 1, 
    );
  

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