我们已经了解了Flutter中的剪裁，那么制作一个评分控件已经很简单了。先准备两个版本的五角星，一个用于高亮展示分数,一般是实心的，另一个用于底图，一般是空心的。使用矩形剪裁(ClipRect)对上一层的五角星进行宽度剪裁。五角星可以使用作图工具做出来，也可以采用自绘图形。
静态展示控件StaticRatingBar
import 'package:flutter/widgets.dart';
import 'dart:math' as Math;
const double kMaxRate = 5.0;
const int kNumberOfStarts = 5;
const double kSpacing = 3.0;
const double kSize = 50.0;
class StaticRatingBar extends StatelessWidget {
/// number of stars
final int count;
/// init rate
final double rate;
/// size of the starts
final double size;
final Color colorLight;
final Color colorDark;
StaticRatingBar({
double rate,
Color colorLight,
Color colorDark,
int count,
this.size: kSize,
}) : rate = rate ?? kMaxRate,
count = count ?? kNumberOfStarts,
colorDark = colorDark ?? new Color(0xffeeeeee),
colorLight = colorLight ?? new Color(0xffFF962E);
Widget buildStar() {
return new SizedBox(
width: size * count,
height: size,
child: new CustomPaint(
painter: new _PainterStars(
size: this.size / 2,
color: colorLight,
style: PaintingStyle.fill,
strokeWidth: 0.0),
));
}
Widget buildHollowStar() {
return new SizedBox(
width: size * count,
height: size,
child: new CustomPaint(
painter: new _PainterStars(
size: this.size / 2,
color: colorDark,
style: PaintingStyle.fill,
strokeWidth: 0.0),
));
}
@override
Widget build(BuildContext context) {
return new Stack(
children: <Widget>[
buildHollowStar(),
new ClipRect(
clipper: new _RatingBarClipper(width: rate * size),
child: buildStar(),
)
],
);
}
}
class _RatingBarClipper extends CustomClipper<Rect> {
final double width;
_RatingBarClipper({this.width}) : assert(width != null);
@override
Rect getClip(Size size) {
return new Rect.fromLTRB(0.0, 0.0, width, size.height);
}
@override
bool shouldReclip(_RatingBarClipper oldClipper) {
return width != oldClipper.width;
}
}
class _PainterStars extends CustomPainter {
final double size;
final Color color;
final PaintingStyle style;
final double strokeWidth;
_PainterStars({this.size, this.color, this.strokeWidth, this.style});
/// 角度转弧度公式
double degree2Radian(int degree) {
return (Math.pi * degree / 180);
}
Path createStarPath(double radius, Path path) {
double radian = degree2Radian(36); // 36为五角星的角度
double radius_in = (radius * Math.sin(radian / 2) / Math.cos(radian)) *
1.1; // 中间五边形的半径,太正不是很好看，扩大一点点
path.moveTo((radius * Math.cos(radian / 2)), 0.0); // 此点为多边形的起点
path.lineTo((radius * Math.cos(radian / 2) + radius_in * Math.sin(radian)),
(radius - radius * Math.sin(radian / 2)));
path.lineTo((radius * Math.cos(radian / 2) * 2),
(radius - radius * Math.sin(radian / 2)));
path.lineTo(
(radius * Math.cos(radian / 2) + radius_in * Math.cos(radian / 2)),
(radius + radius_in * Math.sin(radian / 2)));
path.lineTo((radius * Math.cos(radian / 2) + radius * Math.sin(radian)),
(radius + radius * Math.cos(radian)));
path.lineTo((radius * Math.cos(radian / 2)), (radius + radius_in));
path.lineTo((radius * Math.cos(radian / 2) - radius * Math.sin(radian)),
(radius + radius * Math.cos(radian)));
path.lineTo(
(radius * Math.cos(radian / 2) - radius_in * Math.cos(radian / 2)),
(radius + radius_in * Math.sin(radian / 2)));
path.lineTo(0.0, (radius - radius * Math.sin(radian / 2)));
path.lineTo((radius * Math.cos(radian / 2) - radius_in * Math.sin(radian)),
(radius - radius * Math.sin(radian / 2)));
path.lineTo((radius * Math.cos(radian / 2)), 0.0);
return path;
}
@override
void paint(Canvas canvas, Size size) {
Paint paint = new Paint();
// paint.color = Colors.redAccent;
paint.strokeWidth = strokeWidth;
paint.color = color;
paint.style = style;
Path path = new Path();
double offset = strokeWidth > 0 ? strokeWidth + 2 : 0.0;
path = createStarPath(this.size - offset, path);
path = path.shift(new Offset(this.size * 2, 0.0));
path = createStarPath(this.size - offset, path);
path = path.shift(new Offset(this.size * 2, 0.0));
path = createStarPath(this.size - offset, path);
path = path.shift(new Offset(this.size * 2, 0.0));
path = createStarPath(this.size - offset, path);
path = path.shift(new Offset(this.size * 2, 0.0));
path = createStarPath(this.size - offset, path);
if (offset > 0) {
path = path.shift(new Offset(offset, offset));
}
path.close();
canvas.drawPath(path, paint);
}
@override
bool shouldRepaint(_PainterStars oldDelegate) {
return oldDelegate.size != this.size;
}
}
使用静态显示评分：
new StaticRatingBar(
size: 20.0,
rate: 4.5,
)
效果:
动态评分控件:
class RatingBar extends StatefulWidget {
/// 回调
final ValueChanged<int> onChange;
/// 大小， 默认 50
final double size;
/// 值 1-5
final int value;
/// 数量 5 个默认
final int count;
/// 高亮
final Color colorLight;
/// 底色
final Color colorDark;
/// 如果有值，那么就是空心的
final double strokeWidth;
/// 越大，五角星越圆
final double radiusRatio;
RatingBar(
{this.onChange,
this.value,
this.size: kSize,
this.count: kNumberOfStarts,
this.strokeWidth,
this.radiusRatio: 1.1,
Color colorDark,
Color colorLight})
: colorDark = colorDark ?? new Color(0xffDADBDF),
colorLight = colorLight ?? new Color(0xffFF962E);
@override
State<StatefulWidget> createState() {
return new _RatingBarState();
}
}
class _PainterStar extends CustomPainter {
final double size;
final Color color;
final PaintingStyle style;
final double strokeWidth;
final double radiusRatio;
_PainterStar(
{this.size, this.color, this.strokeWidth, this.style, this.radiusRatio});
@override
void paint(Canvas canvas, Size size) {
Paint paint = new Paint();
paint.strokeWidth = strokeWidth;
paint.color = color;
paint.style = style;
Path path = new Path();
double offset = strokeWidth > 0 ? strokeWidth + 2 : 0.0;
path = createStarPath(this.size - offset, radiusRatio, path);
if (offset > 0) {
path = path.shift(new Offset(offset, offset));
}
path.close();
canvas.drawPath(path, paint);
}
@override
bool shouldRepaint(_PainterStar oldDelegate) {
return oldDelegate.size != this.size ||
oldDelegate.color != this.color ||
oldDelegate.strokeWidth != this.strokeWidth;
}
}
class _RatingBarState extends State<RatingBar> {
int _value;
@override
void initState() {
_value = widget.value;
super.initState();
}
Widget buildItem(int index, double size, count) {
bool selected = _value != null && _value > index;
bool stroke = widget.strokeWidth != null && widget.strokeWidth > 0;
return new GestureDetector(
onTap: () {
if (widget.onChange != null) {
widget.onChange(index + 1);
}
setState(() {
_value = index + 1;
});
},
behavior: HitTestBehavior.opaque,
child: new SizedBox(
width: size,
height: size,
child: new CustomPaint(
painter: new _PainterStar(
radiusRatio: widget.radiusRatio,
size: size / 2,
color: selected ? widget.colorLight : widget.colorDark,
style: !selected && stroke
? PaintingStyle.stroke
: PaintingStyle.fill,
strokeWidth: !selected && stroke ? widget.strokeWidth : 0.0),
)),
);
}
@override
Widget build(BuildContext context) {
double size = widget.size;
int count = widget.count;
List<Widget> list = [];
for (int i = 0; i < count; ++i) {
list.add(buildItem(i, size, count));
}
return new Row(
children: list,
);
}
}
转自：代码地址
