flutter 的框架已经为我们提供了很多很多好用的 widget,已经能够满足绝大部分的业务需求,但是,还是有很多很多需求,无法直接通过其组件实现,比如音视频小窗,任务队列,剪切一些不规则形状的图片等等,本篇即为探究 canva, paint 等api 所制作的简单 demo.
下面,我直接从需求出发,实现,并且拖展一些其他的 API测试,先展示一下测试的结果.
设计思路
一开始我是想着完全通过手绘去绘制这个圆形水波球的进度百分比的,然后在水波高点绘制圆弧,这里就涉及到了一个问题,画角度圆弧好画,但是需要计算出当前两个高点的坐标,如下图
经过了七七八八的计算,计算是算出来了
实际代码
import 'dart:math' as math;
import 'dart:ui' as ui;
import 'package:flutter/material.dart';
import 'package:flutter_psd/common/entities/user_entity/card_bag.dart';
import 'package:flutter_psd/common/utils/psdllog.dart';
class WaveIndicator extends StatefulWidget {
/// 0~1之间的值
final double value;
final Color color;
final BorderRadius? borderRadius;
final Widget? child;
final int? colorMode;
const WaveIndicator({
Key? key,
required this.value,
required this.color,
this.borderRadius,
this.colorMode,
this.child,
}) : super(key: key);
@override
_WaveIndicatorState createState() => _WaveIndicatorState();
}
class _WaveIndicatorState extends State<WaveIndicator> {
@override
Widget build(BuildContext context) {
Widget wrap;
wrap = Stack(
children: [
Container(
width: 100,
height: 100, // color: Colors.red,
child: Wave(
value: widget.value,
color: widget.color,
child: widget.child,
colorMode: widget.colorMode,
),
),
],
);
if (widget.borderRadius != null) {
wrap = ClipRRect(
borderRadius: widget.borderRadius!,
child: wrap,
);
}
return wrap;
}
}
class Wave extends StatefulWidget {
final double value;
final Color color;
final Widget? child;
final int? colorMode;
const Wave(
{Key? key,
required this.value,
required this.color,
this.colorMode,
this.child})
: super(key: key);
@override
_WaveState createState() => _WaveState();
}
class _WaveState extends State<Wave> with SingleTickerProviderStateMixin {
late AnimationController _controller;
@override
void initState() {
super.initState();
_controller = AnimationController(
vsync: this,
duration: Duration(milliseconds: 1500),
)..repeat();
}
@override
void dispose() {
_controller.dispose();
super.dispose();
psdllog('$runtimeType被释放了');
}
@override
Widget build(BuildContext context) {
return AnimatedBuilder(
animation: _controller,
builder: (BuildContext context, Widget? child) {
return Container(
child: CustomPaint(
painter: _WavePainter(
value: widget.value,
animateValue: _controller.value,
color: widget.color,
colorMode: widget.colorMode,
),
child: widget.child,
));
});
}
}
class _WavePainter extends CustomPainter {
final double value;
final double animateValue;
final Color color;
final int? colorMode;
_WavePainter({
required this.value,
required this.animateValue,
required this.color,
this.colorMode,
});
// assert(value == null),
// assert(animateValue != null),
// assert(color != null),
@override
void paint(Canvas canvas, Size size) {
Paint paint = Paint()
// ..color = this.color
..style = PaintingStyle.fill;
if(this.colorMode == 0) {
paint.shader = ui.Gradient.sweep(Offset(size.width / 2, size.height / 2),
[Colors.red, Colors.yellow]);
} else if(this.colorMode == 1) {
paint.shader = ui.Gradient.linear(ui.Offset(size.width / 2, 0),ui.Offset(size.width / 2, size.height), [Colors.red, Colors.yellow]);
} else if(this.colorMode == 2) {
paint.shader = ui.Gradient.radial(Offset(size.width / 2, size.height / 2), math.min(size.width / 2, size.height / 2), [Colors.red, Colors.yellow]);
}
;
psdllog(size);
canvas.drawPath(_getPath(size), paint);
}
Path _getPath(Size size) {
Path path = Path()
..addPolygon(_generateVerticalWavePath(size), false)
..lineTo(size.width, size.height)
..lineTo(0.0, size.height)
..close();
return path;
}
List<Offset> _generateVerticalWavePath(Size size) {
final waveList = <Offset>[];
for (int i = -2; i <= size.width.toInt() + 2; i++) {
final waveHeight = (size.height / 20);
final dy = math.sin((animateValue * 360 - i) % 360 * (math.pi / 180)) *
waveHeight +
(size.height - (size.height * value));
waveList.add(Offset(i.toDouble(), dy));
}
return waveList;
}
@override
bool shouldRepaint(covariant _WavePainter oldDelegate) {
return animateValue != oldDelegate.animateValue ||
value != oldDelegate.value;
}
}
整个代码其实很简单,写一个外层容器WaveIndicator,然后写一个水波效果Wave,就没了.
代码中有些内容其实没有进行封装,主要是我写着写着,然后开始魔改了,瞎测试 API,比如 color 这东西我就没有实现,因为我后面测试渐变 demo 去了.
这里说明一下,水波路径是参照liquid_progress_indicator)的写法写的(由于我自己写了半天路径,陷入了一个误区,以为这段是用贝塞尔写的,效果一直不好,所以在网上查来查去,才发现是用三角函数来做,最后查到了这个组件,不得不说,人家的代码真的写的好),我由于是测试 CustomPaint,所以没有使用人家的 CustomClipper.
List<Offset> _generateVerticalWavePath(Size size) {
final waveList = <Offset>[];
for (int i = -2; i <= size.width.toInt() + 2; i++) {
final waveHeight = (size.height / 20);
final dy = math.sin((animateValue * 360 - i) % 360 * (math.pi / 180)) *
waveHeight +
(size.height - (size.height * value));
waveList.add(Offset(i.toDouble(), dy));
}
return waveList;
}
以水平水波为例子,这个水波路径的核心,其实是将width均分成 width 宽度个 count,然后每个index高度为final dy = math.sin((animateValue * 360 - i) % 360 * (math.pi / 180)) * waveHeight + (size.height - (size.height * value));,通过[0,1]放大到[0,360] (因为一个峰谷值为2π),然后* (math.pi / 180)转换成弧度,取 sin 函数,乘以波浪高度waveHeight,最后加上value 值(size.height - (size.height * value))
拖展
liquid_progress_indicator)这里主要是为了实现水波球,我主要是为了测试画笔的 api,然后就测试 shaper,colorFilter等等.这里就不放出来了,实际上的效果也如上面所示,radial,linear效果我不用多说,sweep 以前在 iOS 端有过业务需求,直播间的连击效果要改成这种功能雷达清扫的效果,所以我还是知道有这种印象的,还有一些渐变进度条的,style 改成 solid 即可.
瞎提的点
顺便提一下,addArc 这个 api,其实叫是 x 轴方向,然后转动方向为顺时针,这里不需要大家测试了
PS
随便吐槽下,flutter 好处就是,如果我想封装控件的话,我可以很快的组合出一个组件,然后在那慢慢调效果,iOS 在这方面是真滴难受.
多读源码!多读源码!多读源码!源码真的能提升你的架构能力
多测试 API!多测试 API!多测试 API!测试 API 不是为了背下来,而是为了知道什么功能大概是什么方向能实现.
