Flutter构建自定义Widgets的全过程记录

import 'package:flutter/material.dart';
 
class CustomButtonTest extends StatelessWidget{
  final String textStr;
  CustomButtonTest(this.textStr);
 
  @override
  Widget build(BuildContext context) {
    return RaisedButton(
      onPressed: (){},
      child: Text(
        textStr,
        textAlign: TextAlign.center,
      )
    );
  }
 
}

@override
  Widget build(BuildContext context) {
    return new Center(
      child: new CustomButton("Custom Button"),
    );
  }
}

Paint _paint = new Paint()
..color = Colors.red // 画笔颜色 
..strokeCap = StrokeCap.round //画笔笔触类型,包括(1.round-画笔笔触呈半圆形轮廓开始和结束;2.butt-笔触开始和结束边缘平坦，没有外延;3.square-笔触开始和结束边缘平坦,向外延伸长度为画笔宽度的一半)
..isAntiAlias = true //是否启动抗锯齿
..style=PaintingStyle.fill //绘画风格，默认为填充，有fill和stroke两种
..blendMode=BlendMode.exclusion //颜色混合模式
..colorFilter=ColorFilter.mode(Colors.blueAccent, BlendMode.exclusion)//颜色渲染模式
..maskFilter=MaskFilter.blur(BlurStyle.inner, 3.0)//模糊遮罩效果
..filterQuality=FilterQuality.high//颜色渲染模式的质量
..strokeWidth = 15.0;//画笔的宽度复制代码

void drawRect(Rect rect, Paint paint) {...} //画矩形
void drawLine(Offset p1, Offset p2, Paint paint) {...} //画线
void drawPoints(PointMode pointMode, List<Offset> points, Paint paint) {...} //画点
void drawCircle(Offset c, double radius, Paint paint) {...} //画圆
void drawArc(Rect rect, double startAngle, double sweepAngle, bool useCenter, Paint paint) {...} //画圆弧

import 'dart:math';
import 'package:flutter/material.dart';
 
class PieChartTest extends StatelessWidget{
  const PieChartTest({Key? key}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('pie chart'),
      ),
      body:Container(
        alignment: Alignment.center,
        child: CustomPaint(
          size: const Size(300, 300),
          painter: PieChartPainter(),
        ),
      )
    );
  }
}
 
class PieChartPainter extends CustomPainter{
 
  Paint getColoredPaint(Color color){
    Paint paint=Paint();
    paint.color=color;
    return paint;
  }
 
  @override
  void paint(Canvas canvas, Size size) {
    double wheelSize=min(size.width, size.height)/2;
    double nbElem=8;
    double radius=(2*pi)/nbElem;
    Rect boundingRect=Rect.fromCircle(center: Offset(wheelSize,wheelSize), radius: wheelSize);
    canvas.drawArc(boundingRect, 0, radius, true, getColoredPaint(Colors.orange));
    canvas.drawArc(boundingRect, radius, radius, true, getColoredPaint(Colors.black));
    canvas.drawArc(boundingRect, radius*2, radius, true, getColoredPaint(Colors.green));
    canvas.drawArc(boundingRect, radius*3, radius, true, getColoredPaint(Colors.red));
    canvas.drawArc(boundingRect, radius*4, radius, true, getColoredPaint(Colors.blue));
    canvas.drawArc(boundingRect, radius*5, radius, true, getColoredPaint(Colors.yellow));
    canvas.drawArc(boundingRect, radius*6, radius, true, getColoredPaint(Colors.purple));
    canvas.drawArc(boundingRect, radius*7, radius, true, getColoredPaint(Colors.white));
  }
 
  @override
  bool shouldRepaint(covariant CustomPainter oldDelegate)=>oldDelegate!=this;
}

final _childWidgetKey = GlobalKey();

ChildPage(key:_receiveKey),

class ChildPage extends StatefulWidget {undefined
ChildPage({Key key}) : super(key: key);
​​​​​​​@override
ChildPageState createState() => ChildPageState();
}

_childWidgetKey.currentState.onRefresh();