如何在给定宽度的小部件中移动文本
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【中文标题】如何在给定宽度的小部件中移动文本【英文标题】:How get moving text in widget with given width 【发布时间】:2019-09-07 01:27:55 【问题描述】:我正在构建一个广播应用程序。就像在 Spotify 中一样,有一个带有当前标题和艺术家的栏,文本应该在一行中并具有给定的宽度。如何让文本从右到左再向后移动?
在使用自制动画的时候,我想有一个固定的移动文本的速度,所以我需要文本小部件的时间和宽度。
是否有执行此操作的包/内置选项? 还是我必须使用自制动画?如果是这样,我怎样才能获得文本小部件的宽度?
控制器和动画:
AnimationController(duration: Duration(seconds: 10), vsync: this);
animation = Tween<double>(begin: 0, end: 1)
.animate(CurvedAnimation(parent: _controller, curve: Curves.linear));
animation.addListener(()
setState(() );
);
_controller.repeat();
构建方法
double value =
-300 * (animation.value <= 0.5 ? animation.value : 1 - animation.value);
return Container(
child: SizedBox(
width: widget.width,
height: 24,
child: Transform.translate(
offset: Offset(value, 0),
child: widget.text,
),
),
);
【问题讨论】:
【参考方案1】:你可以这样做:
import 'dart:async';
import 'package:flutter/material.dart';
class ScrollingText extends StatefulWidget
final String text;
final TextStyle textStyle;
final Axis scrollAxis;
final double ratioOfBlankToScreen;
ScrollingText(
@required this.text,
this.textStyle,
this.scrollAxis: Axis.horizontal,
this.ratioOfBlankToScreen: 0.25,
) : assert(text != null,);
@override
State<StatefulWidget> createState()
return ScrollingTextState();
class ScrollingTextState extends State<ScrollingText>
with SingleTickerProviderStateMixin
ScrollController scrollController;
double screenWidth;
double screenHeight;
double position = 0.0;
Timer timer;
final double _moveDistance = 3.0;
final int _timerRest = 100;
GlobalKey _key = GlobalKey();
@override
void initState()
super.initState();
scrollController = ScrollController();
WidgetsBinding.instance.addPostFrameCallback((callback)
startTimer();
);
void startTimer()
if (_key.currentContext != null)
double widgetWidth =
_key.currentContext.findRenderObject().paintBounds.size.width;
double widgetHeight =
_key.currentContext.findRenderObject().paintBounds.size.height;
timer = Timer.periodic(Duration(milliseconds: _timerRest), (timer)
double maxScrollExtent = scrollController.position.maxScrollExtent;
double pixels = scrollController.position.pixels;
if (pixels + _moveDistance >= maxScrollExtent)
if (widget.scrollAxis == Axis.horizontal)
position = (maxScrollExtent -
screenWidth * widget.ratioOfBlankToScreen +
widgetWidth) /
2 -
widgetWidth +
pixels -
maxScrollExtent;
else
position = (maxScrollExtent -
screenHeight * widget.ratioOfBlankToScreen +
widgetHeight) /
2 -
widgetHeight +
pixels -
maxScrollExtent;
scrollController.jumpTo(position);
position += _moveDistance;
scrollController.animateTo(position,
duration: Duration(milliseconds: _timerRest), curve: Curves.linear);
);
@override
void didChangeDependencies()
super.didChangeDependencies();
screenWidth = MediaQuery.of(context).size.width;
screenHeight = MediaQuery.of(context).size.height;
Widget getBothEndsChild()
if (widget.scrollAxis == Axis.vertical)
String newString = widget.text.split("").join("\n");
return Center(
child: Text(
newString,
style: widget.textStyle,
textAlign: TextAlign.center,
),
);
return Center(
child: Text(
widget.text,
style: widget.textStyle,
));
Widget getCenterChild()
if (widget.scrollAxis == Axis.horizontal)
return Container(width: screenWidth * widget.ratioOfBlankToScreen);
else
return Container(height: screenHeight * widget.ratioOfBlankToScreen);
@override
void dispose()
super.dispose();
if (timer != null)
timer.cancel();
@override
Widget build(BuildContext context)
return ListView(
key: _key,
scrollDirection: widget.scrollAxis,
controller: scrollController,
physics: NeverScrollableScrollPhysics(),
children: <Widget>[
getBothEndsChild(),
getCenterChild(),
getBothEndsChild(),
],
);
并像这样使用小部件:
ScrollingText(
text: text,
textStyle: TextStyle(fontSize: 12),
)
【讨论】:
如果你使用 Marquee(另一个答案)或者这个答案,不要忘记把它放在一个容器中并给它高度和宽度,因为 Marque 和上面的例子是listview
【参考方案2】:
使用来自 pub.dev marquee 的这个小部件。
Marquee(
text: 'There once was a boy who told this story about a boy: "',
)
【讨论】:
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