是一个饼状图，但是不适用，因为数据比较多的时候显示就很密集，所以要用线，添加了一些，不过目前文字大小还没怎么计算，所以是写固定的

整个代码如下

import 'package:flutter/material.dart';

import 'piechart.dart';

import 'PieData.dart';

import 'dart:math';

class View extends CustomPainter{

//中间文字

var text='111';

bool isChange=false;

//当前选中的扇形

var currentSelect=0;

//画笔

Paint _mPaint;

Paint TextPaint;

// 扇形大小

int mWidth, mHeight;

// 圆半径

num mRadius, mInnerRadius,mBigRadius;

// 扇形起始弧度(Andorid中是角度)

num mStartAngle = 0;

// 矩形(扇形绘制的区域)

Rect mOval,mBigOval;

// 扇形 数据

List mData;

PieData pieData;

// 构造函数，接受需要的参数值

View(this.mData,this.pieData,this.currentSelect,this.isChange);

/**

* 重写 paint方法，在其中写绘制饼状图的逻辑

*/

@override

void paint(Canvas canvas, Size size) {

// 初始化各类工具等

_mPaint = new Paint();

TextPaint = new Paint();

mHeight=100;mWidth=100;

/// 生成纵轴文字的TextPainter

TextPainter textPainter = TextPainter(

textDirection: TextDirection.ltr,

maxLines: 1,

);

// 文字画笔 风格定义

TextPainter _newVerticalAxisTextPainter(String text) {

return textPainter

..text = TextSpan(

text: text,

style: new TextStyle(

color: Colors.black,

fontSize: 10.0,

),

);

}

// 正常半径

mRadius = 50.0;

//加大半径 用来绘制被选中的扇形区域

mBigRadius=55.0;

//內园半径

mInnerRadius = mRadius * 0.50;

// 未选中的扇形绘制的矩形区域

mOval = Rect.fromLTRB(-mRadius, -mRadius, mRadius, mRadius);

// 选中的扇形绘制的矩形区域

mBigOval = Rect.fromLTRB(-mBigRadius, -mBigRadius, mBigRadius,

mBigRadius);

//当没有数据时 直接返回

if (mData.length == null || mData.length <= 0) {

return;

}

///绘制逻辑与Android差不多

canvas.save();

// 将坐标点移动到View的中心

canvas.translate(50.0, 50.0);

// 1. 画扇形

num startAngle = 0.0;

bool draw=false;

for (int i = 0; i < mData.length; i++) {

PieData p = mData[i];

double hudu=p.percentage;

//计算当前偏移量(单位为弧度)

double sweepAngle = 2*pi*hudu;

// print(sweepAngle);

//画笔的颜色

_mPaint..color = p.color;

if(currentSelect>=0 && i==currentSelect){

//如果当前为所选中的扇形 则将其半径加大 突出显示

canvas.drawArc(mBigOval, startAngle, sweepAngle, true, _mPaint);

Paint _paint=new Paint();

_paint.color=Color(0xff91c954);

_paint.strokeWidth=1.0;

Offset offset=Offset(mRadius*0.75*cos(startAngle+sweepAngle/2.0),mRadius*0.75*sin(startAngle+sweepAngle/2.0));

// print(mRadius*0.75*sin(2*pi*270.0/360.0));

// print(mRadius*0.75*cos(2*pi*270.0/360.0));

// if(!draw){print(offset);

//print(mRadius*0.75*sin(2*pi*270.0/360.0));

// print(mRadius*0.75*cos(2*pi*270.0/360.0));

TextPainter t=TextPainter(text: TextSpan(text: "11%",style: TextStyle(color: Colors.black),),textDirection: TextDirection.ltr,

maxLines: 1,);

canvas.drawLine(offset, Offset(mRadius*1.25*cos(startAngle+sweepAngle/2.0),mRadius*1.25*sin(startAngle+sweepAngle/2.0)), _paint);

if(mRadius*0.75*cos(startAngle+sweepAngle/2.0)<0){

Offset offset1=new Offset(mRadius*1.25*cos(startAngle+sweepAngle/2.0)-mRadius*0.2, mRadius*1.25*sin(startAngle+sweepAngle/2.0));

canvas.drawLine(Offset(mRadius*1.25*cos(startAngle+sweepAngle/2.0),mRadius*1.25*sin(startAngle+sweepAngle/2.0)), offset1, _paint);

// canvas.restore();

t.layout();

t.paint(canvas, Offset(mRadius*1.25*cos(startAngle+sweepAngle/2.0)-mRadius*0.2-20.0, mRadius*1.25*sin(startAngle+sweepAngle/2.0)-10.0));

}else{

Offset offset1=new Offset(mRadius*1.25*cos(startAngle+sweepAngle/2.0)+mRadius*0.2, mRadius*1.25*sin(startAngle+sweepAngle/2.0));

canvas.drawLine(Offset(mRadius*1.25*cos(startAngle+sweepAngle/2.0),mRadius*1.25*sin(startAngle+sweepAngle/2.0)), offset1, _paint);

// canvas.restore();

t.layout();

t.paint(canvas, Offset(mRadius*1.25*cos(startAngle+sweepAngle/2.0)-mRadius*0.2+20.0, mRadius*1.25*sin(startAngle+sweepAngle/2.0)-10.0));

}

// draw=true;

// }

}else{

// 绘制没被选中的扇形 正常半径

canvas.drawArc(mOval, startAngle, sweepAngle, true, _mPaint);

Offset origin=Offset((-mRadius+mRadius)/2.0, (-mRadius+mRadius)/2.0);

Paint _paint=new Paint();

_paint.color=Color(0xff91c954);

_paint.strokeWidth=1.0;

Offset offset=Offset( mRadius*0.75*cos(startAngle+sweepAngle/2.0),mRadius*0.75*sin(startAngle+sweepAngle/2.0));

canvas.drawLine(offset, Offset(mRadius*1.25*cos(startAngle+sweepAngle/2.0),mRadius*1.25*sin(startAngle+sweepAngle/2.0)), _paint);

TextPainter t=TextPainter(text: TextSpan(text: "11%",style: TextStyle(color: Colors.black),),textDirection: TextDirection.ltr,

maxLines: 1,);

if(mRadius*0.75*cos(startAngle+sweepAngle/2.0)<0){

Offset offset1=new Offset(mRadius*1.25*cos(startAngle+sweepAngle/2.0)-mRadius*0.2, mRadius*1.25*sin(startAngle+sweepAngle/2.0));

canvas.drawLine(Offset(mRadius*1.25*cos(startAngle+sweepAngle/2.0),mRadius*1.25*sin(startAngle+sweepAngle/2.0)), offset1, _paint);

// canvas.restore();

t.layout();

t.paint(canvas, Offset(mRadius*1.25*cos(startAngle+sweepAngle/2.0)-mRadius*0.2-25.0, mRadius*1.25*sin(startAngle+sweepAngle/2.0)-10.0));

}else{

Offset offset1=new Offset(mRadius*1.25*cos(startAngle+sweepAngle/2.0)+mRadius*0.2, mRadius*1.25*sin(startAngle+sweepAngle/2.0));

canvas.drawLine(Offset(mRadius*1.25*cos(startAngle+sweepAngle/2.0),mRadius*1.25*sin(startAngle+sweepAngle/2.0)), offset1, _paint);

// canvas.restore();

t.layout();

t.paint(canvas, Offset(mRadius*1.25*cos(startAngle+sweepAngle/2.0)-mRadius*0.2+20.0, mRadius*1.25*sin(startAngle+sweepAngle/2.0)-10.0));

}

// draw=true;

// }

}

//计算每次开始绘制的弧度

startAngle += sweepAngle ;

// print(startAngle);

}

// canvas.drawRect(mOval, _mPaint); // 矩形区域

// 2.画内圆

_mPaint..color = Colors.white;

canvas.drawCircle(Offset.zero, mInnerRadius, _mPaint);

canvas.restore();

//当前百分比值

double percentage = pieData.percentage*100;

// 绘制文字内容

var texts ='${percentage}%';

var tp = _newVerticalAxisTextPainter(texts)..layout();

// Text的绘制起始点 = 可用宽度 - 文字宽度 - 左边距

var textLeft = 35.0;

tp.paint(canvas, Offset(textLeft, 50.0 - tp.height / 2));

}

@override

bool shouldRepaint(CustomPainter oldDelegate) {

return true;

}

}

绘制text之前，一定要调用layout这个函数，这个跟安卓很像