本站精选了一篇相关的编程文章，网友充博文根据主题投稿了本篇教程内容，涉及到Flutter、投票组件、Flutter投票组件相关内容，已被772网友关注，下面的电子资料对本篇知识点有更加详尽的解释。
Flutter投票组件
本文实例为大家分享了Flutter投票组件的使用方法，供大家参考，具体内容如下
前景
基于公司项目需求，仿照微博实现投票功能。
开发遇到的问题
1.选项列表的高度，自适应的问题；
2.进度条动画的问题；
3.列表回收机制，导致进度条动画重复；
4.自定义进度条四周圆角；
如何解决问题
- 拿到数组列表最长的数据，然后根据屏幕宽度计算，超出一行则设定两行高度，否则使用一行的高度；
_didExceedOneMoreLines(String text, double width, TextStyle style) {
final span = TextSpan(text: text, style: style);
final tp =
TextPainter(text: span, maxLines: 1, textDirection: TextDirection.ltr);
tp.layout(maxWidth: width);
if (tp.didExceedMaxLines) {
//设置item选项的高度
_itemHeight = 100.w;
}
}- Widget控件初始化（initState）方法时，使用AnimationController动画，并实现SingleTickerProviderStateMixin，在build方法当中调用 _controller.animateTo()
AnimationController _controller;
_controller = AnimationController(
vsync: this,
duration: const Duration(seconds: 1),
)..addListener(() {
setState(() {});
});
//触发动画，执行的位置
_controller.animateTo()- 在列表数据当中给动画标记字段，让其是否执行动画；当用户投票成功，改变状态执行进度条动画。用户滑动列表之后，将标记改为false。关闭动画效果。
- 针对修改部分源码，设置进度条圆角控件；
import 'package:flutter/cupertino.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:flutter_screenutil/flutter_screenutil.dart';
class RoundLinearProgressPainter extends ProgressIndicator {
const RoundLinearProgressPainter({
Key key,
double value,
Color backgroundColor,
Color color,
Animation valueColor,
this.minHeight,
String semanticsLabel,
String semanticsValue,
}) : assert(minHeight == null || minHeight > 0),
super(
key: key,
value: value,
backgroundColor: backgroundColor,
color: color,
valueColor: valueColor,
semanticsLabel: semanticsLabel,
semanticsValue: semanticsValue,
);
final double minHeight;
@override
_RoundLinearProgressPainterState createState() =>
_RoundLinearProgressPainterState();
}
class _RoundLinearProgressPainterState extends State
with SingleTickerProviderStateMixin {
AnimationController _controller;
@override
void initState() {
super.initState();
_controller = AnimationController(
duration: const Duration(milliseconds: 1),
vsync: this,
)..addListener(() {
setState(() {});
});
if (widget.value != null) _controller.forward();
}
@override
Widget build(BuildContext context) {
return widget._buildSemanticsWrapper(
context: context,
child: Container(
constraints: BoxConstraints(
minWidth: double.infinity,
minHeight: widget.minHeight ?? 4.0,
),
child: CustomPaint(
painter: _LinearProgressIndicatorPainter(
backgroundColor: widget._getBackgroundColor(context),
valueColor: widget._getValueColor(context),
value: widget.value,
animationValue: _controller.value,
),
),
),
);
}
@override
void didUpdateWidget(RoundLinearProgressPainter oldWidget) {
super.didUpdateWidget(oldWidget);
if (widget.value == null && !_controller.isAnimating)
_controller.repeat();
else if (widget.value != null && _controller.isAnimating)
_controller.stop();
}
@override
void dispose() {
_controller.dispose();
super.dispose();
}
}
class _LinearProgressIndicatorPainter extends CustomPainter {
const _LinearProgressIndicatorPainter({
this.backgroundColor,
this.valueColor,
this.value,
this.animationValue,
});
final Color backgroundColor;
final Color valueColor;
final double value;
final double animationValue;
@override
void paint(Canvas canvas, Size size) {
final Paint paint = Paint()
..color = backgroundColor
..isAntiAlias = true
..style = PaintingStyle.fill;
canvas.drawRect(Offset.zero & size, paint);
paint.color = valueColor;
void drawBar(double x, double width) {
if (width <= 0.0) return;
RRect rRect;
///圆角的宽度
var radius = Radius.circular(8.w);
if (value == 1.0) {
///当进度条为1时，设置四周圆角
rRect = RRect.fromRectAndRadius(
Offset(0.0, 0.0) & Size(width, size.height), radius);
} else {
///小于1时，设置左侧圆角
rRect = RRect.fromRectAndCorners(
Offset(0.0, 0.0) & Size(width, size.height),
topLeft: radius,
bottomLeft: radius);
}
canvas.drawRRect(rRect, paint);
}
if (value != null) {
drawBar(0.0, value.clamp(0.0, 1.0) * size.width);
}
}
@override
bool shouldRepaint(_LinearProgressIndicatorPainter oldPainter) {
return oldPainter.backgroundColor != backgroundColor ||
oldPainter.valueColor != valueColor ||
oldPainter.value != value ||
oldPainter.animationValue != animationValue;
}
}
abstract class ProgressIndicator extends StatefulWidget {
const ProgressIndicator({
Key key,
this.value,
this.backgroundColor,
this.color,
this.valueColor,
this.semanticsLabel,
this.semanticsValue,
}) : super(key: key);
final double value;
final Color backgroundColor;
final Color color;
final Animation valueColor;
final String semanticsLabel;
final String semanticsValue;
Color _getBackgroundColor(BuildContext context) =>
backgroundColor ?? Theme.of(context).colorScheme.background;
Color _getValueColor(BuildContext context) =>
valueColor?.value ?? color ?? Theme.of(context).colorScheme.primary;
@override
void debugFillProperties(DiagnosticPropertiesBuilder properties) {
super.debugFillProperties(properties);
properties.add(PercentProperty('value', value,
showName: false, ifNull: ''));
}
Widget _buildSemanticsWrapper({
BuildContext context,
Widget child,
}) {
String expandedSemanticsValue = semanticsValue;
if (value != null) {
expandedSemanticsValue ??= '${(value * 100).round()}%';
}
return Semantics(
label: semanticsLabel,
value: expandedSemanticsValue,
child: child,
);
}
} 以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持码农之家。
