Flutter自定义之钟表

效果

clock.gif

绘制控件（四大角色）

• CustomPaint
• CustomPainter
• Canvas
• Paint

CustomPaint

英文翻译：自定义绘制；CustomPaint可以实现很多酷炫的动画和效果。CustomPaint 提供了让用户自定义widget的能力，它暴露了一个canvas，可以通过这个canvas来绘制widget，CustomPaint会先调用painter绘制背景，然后再绘制child，最后调用foregroundPainter来绘制前景，CustomPaint的定义如下

CustomPaint({Key key, 
      CustomPainter painter,
      CustomPainter foregroundPainter,
      Size size: Size.zero, 
      bool isComplex: false, 
      bool willChange: false, 
      Widget child })
  

• painter：负责绘制背景的painter

• foregroundPainter : 负责绘制前景的painter

• size : 控件大小

• isComplex ： 是否复杂绘制，需要用cache来提高绘制效率

• willChange ： 和isComplex配合使用，当启用缓存时，该属性代表在下一帧中绘制是否会改变

• child ： 子widget

CustomPainter

CustomPaint的绘制过程都将会交给CustomPainter来完成，CustomPainter是个抽象接口，在子类继承CustomPainter的时候必须要重写它的paint 跟 shouldRepaint接口。

class MyCustomPainter extends CustomPainter { 
 //绘制自定义的效果  
@override  void paint(Canvas canvas, Size size) {
} 
 //判断是否需要重新绘制ui 通常在当前实例和旧实例属性不一致时返回true。 
 @override  bool shouldRepaint(MyCustomPainter oldDelegate) {   
        return this != oldDelegate; 
 }
}

• paint : 每当CustomPaint需要重绘的时候都会调用此接口
• shouldRepaint ： 当CustomPaint被重新设置了一个新的painter后会回调此方法，CustomPaint会根据shouldRepaint的返回值来判断是否需要重新绘制ui，譬如新的painter跟旧的painter绘制的内容不一样时，此时shouldRepaint需要返回true来通知CustomPaint重新绘制。

Canvas

Canvas：画布，真正的绘制是由canvas跟paint来完成的，画布提供了各种绘制的接口来绘制图形。 常用的绘制接口有更多请查看官方文档

小知识点：

• canvas.save(); 画布将当前的状态保存

• canvas.restore(); 画布取出原来所保存的状态

Paint

Paint：画笔，是用来在画布上面绘制图形。画笔属性：颜色、线宽、绘制模式、抗锯齿等等。

常用属性有：

• isAntiAlias ： 设置画笔是否扛锯齿

• color : 颜色

• strokeWidth ： 设置画笔画线宽度

• style ：绘制模式，画线或充满

四大法则

1、效果功能分析。
2、功能拆解。
3、功能参数。
4、功能代码实现。

1、效果功能分析。

钟表

2、功能拆解。

• 绘制边框

  void drawCircle(Offset c, double radius, Paint paint)
  

• 绘制刻度

  void drawPoints(PointMode pointMode, List points, Paint paint)
  

• 绘制数字

  TextPainter(
    textAlign: TextAlign.center,
    textDirection: TextDirection.ltr,
    text: TextSpan(),
  ) ..layout()
    ..paint(canvas, offset);
  

• 绘制时针

  void drawLine(Offset p1, Offset p2, Paint paint)
  

• 绘制分针

  void drawLine(Offset p1, Offset p2, Paint paint)
  

• 绘制秒针

• void drawLine(Offset p1, Offset p2, Paint paint)
  

• 绘制中间圆圈

  void drawCircle(Offset c, double radius, Paint paint)
  

• 绘制移动小球

  void drawCircle(Offset c, double radius, Paint paint)
  

• 移动

   Timer.periodic(Duration(seconds: 1), (timer) {
      setState(() {
        dateTime = DateTime.now();
      });
  });
  

3、功能参数

• 钟表的半径
• 边框的颜色
• 刻度的颜色
• 数字的颜色
• 时针的颜色
• 分针的颜色
• 秒针的颜色
• 走秒小球颜色
• 中间圆颜色

4、功能代码实现

从功能拆解可以看出，所有的功能未知数就是位置的计算，我们可以先计算下点的坐标。

刻度点位置计算.jpg

所以圆内所有点的坐标都是

坐标点：（r+l*sina,r-l*cosa）

诱导公式

诱导公式.jpg

时分秒.jpg

完整代码

import 'dart:async';
import 'dart:math';
import 'dart:ui';

import 'package:flutter/material.dart';

///时钟
class ClockView extends StatefulWidget {
  const ClockView({
    Key key,
    this.radius = 150,
    this.borderColor = Colors.black,
    this.scaleColor = Colors.black,
    this.numberColor = Colors.black,
    this.moveBallColor = Colors.red,
    this.hourHandColor = Colors.black,
    this.minuteHandColor = Colors.black,
    this.secondHandColor = Colors.red,
    this.middleCircleColor = Colors.red,
  }) : super(key: key);

  //钟表的半径
  final double radius;

  //边框的颜色
  final Color borderColor;

  //刻度的颜色
  final Color scaleColor;

  //数字的颜色
  final Color numberColor;

  //走秒小球颜色
  final Color moveBallColor;

  //时针的颜色
  final Color hourHandColor;

  //分针的颜色
  final Color minuteHandColor;

  //秒针的颜色
  final Color secondHandColor;

  //中间圆颜色
  final Color middleCircleColor;

  @override
  State createState() {
    return ClockViewState();
  }
}

class ClockViewState extends State {
  //当前时间
  DateTime dateTime;

  //定时器
  Timer timer;

  @override
  void initState() {
    super.initState();
    dateTime = DateTime.now();
    timer = Timer.periodic(Duration(seconds: 1), (timer) {
      setState(() {
        dateTime = DateTime.now();
      });
    });
  }

  @override
  void dispose() {
    //取消定时器
    if (timer.isActive) {
      timer?.cancel();
    }
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return CustomPaint(
      painter: ClockPainter(
        dateTime,
        radius: widget.radius,
        borderColor: this.widget.borderColor,
        scaleColor: this.widget.scaleColor,
        numberColor: this.widget.numberColor,
        moveBallColor: this.widget.moveBallColor,
        hourHandColor: this.widget.hourHandColor,
        minuteHandColor: this.widget.minuteHandColor,
        secondHandColor: this.widget.secondHandColor,
        middleCircleColor: this.widget.middleCircleColor,
      ),
      size: Size(widget.radius * 2, widget.radius * 2),
    );
  }
}

class ClockPainter extends CustomPainter {
  //边框的颜色
  final Color borderColor;

  //刻度的颜色
  final Color scaleColor;

  //数字的颜色
  final Color numberColor;

  //中间圆颜色
  final Color middleCircleColor;

  //走秒小球颜色
  final Color moveBallColor;

  //时针的颜色
  final Color hourHandColor;

  //分针的颜色
  final Color minuteHandColor;

  //秒针的颜色
  final Color secondHandColor;

  //边框画笔的宽度
  double borderWidth;

  //刻度画笔的宽度
  double scaleWidth;

  //数字画笔的宽度
  double numberWidth;

  //时针画笔的宽度
  double hourHandWidth;

  //分针画笔的宽度
  double minuteHandWidth;

  //秒针画笔的宽度
  double secondHandWidth;

  //中间圆的宽度
  double middleCircleWidth;

  //小刻度的位置集合
  List scaleOffset = [];

  //大刻度的位置集合 每5个小刻度是一个大刻度
  List bigScaleOffset = [];

  //钟表的半径
  final double radius;

  //当前时间
  final DateTime dateTime;

  //边框画笔
  Paint borderPaint;

  //刻度画笔
  Paint scalePaint;

  //大刻度画笔
  Paint biggerScalePaint;

  //数字画笔
  TextPainter textPainter;

  //时针画笔
  Paint hourPaint;

  //分针画笔
  Paint minutePaint;

  //秒针画笔
  Paint secondPaint;

  //中间圆画笔
  Paint centerPaint;

  //移动小球画笔
  Paint moveBallPaint;

  ClockPainter(
    this.dateTime, {
    this.radius,
    this.borderColor,
    this.scaleColor,
    this.numberColor,
    this.moveBallColor,
    this.hourHandColor,
    this.minuteHandColor,
    this.secondHandColor,
    this.middleCircleColor,
  }) {
    //根据自己的审美设置这些画笔的宽度
    borderWidth = 8 * (radius / 100);
    scaleWidth = 2 * (radius / 100);
    numberWidth = 20 * (radius / 100);
    hourHandWidth = 5 * (radius / 100);
    minuteHandWidth = 3 * (radius / 100);
    secondHandWidth = 1 * (radius / 100);
    middleCircleWidth = 4 * (radius / 100);

    //边框画笔
    borderPaint =
        createPaint(borderColor, borderWidth, style: PaintingStyle.stroke);
    //刻度画笔
    scalePaint = createPaint(numberColor, scaleWidth);
    //大刻度
    biggerScalePaint = createPaint(numberColor, scaleWidth * 2);
    //时针画笔
    hourPaint = createPaint(hourHandColor, hourHandWidth);
    //分针画笔
    minutePaint = createPaint(minuteHandColor, minuteHandWidth);
    //秒针画笔
    secondPaint = createPaint(secondHandColor, secondHandWidth);
    //中间圆
    centerPaint = createPaint(middleCircleColor, middleCircleWidth);
    //移动小球画笔
    moveBallPaint = createPaint(moveBallColor, scaleWidth * 2);
    //数字
    textPainter = TextPainter(
      textAlign: TextAlign.center,
      textDirection: TextDirection.ltr,
    );

    //计算出 小刻度和大刻度
    final l = radius - borderWidth * 2;
    for (var i = 0; i < 60; i++) {
      Offset offset = pointOffset(radius, l, 360 / 60 * i);
      //小刻度
      scaleOffset.add(offset);
      //大刻度
      if (i % 5 == 0) {
        bigScaleOffset.add(offset);
      }
    }
  }

  @override
  void paint(Canvas canvas, Size size) {
    //绘制边框
    drawBorder(canvas);
    //绘制刻度
    drawScale(canvas);
    //绘制数字
    drawNumber(canvas);
    //绘制时针
    drawHour(canvas);
    //绘制分针
    drawMinute(canvas);
    //绘制秒针
    drawSecond(canvas);
    //绘制中间圆圈
    drawMiddleCircle(canvas);
    //绘制移动小球
    drawMoveBall(canvas);
  }

  //判断是否需要重绘
  @override
  bool shouldRepaint(CustomPainter oldDelegate) {
    return true;
  }

  ///绘制边框
  void drawBorder(Canvas canvas) {
    canvas.drawCircle(
        Offset(radius, radius), radius - borderWidth / 2, borderPaint);
  }

  ///绘制刻度
  void drawScale(Canvas canvas) {
    //小刻度
    canvas.drawPoints(PointMode.points, scaleOffset, scalePaint);
    //大刻度
    canvas.drawPoints(PointMode.points, bigScaleOffset, biggerScalePaint);
  }

  ///绘制数字
  void drawNumber(Canvas canvas) {
    double l = radius - borderWidth * 4;
    for (var i = 0; i < bigScaleOffset.length; i++) {
      textPainter.text = TextSpan(
        text: "${i == 0 ? 12 : i}",
        style: TextStyle(color: numberColor, fontSize: numberWidth),
      );
      Offset offset = pointOffset(radius, l, i * 360 / 12);
      textPainter.layout();
      textPainter.paint(
          canvas,
          Offset(
            offset.dx - (textPainter.width / 2),
            offset.dy - (textPainter.height / 2),
          ));
    }
  }

  ///绘制时针
  void drawHour(Canvas canvas) {
    final hour = dateTime.hour;
    double angle = 360 / 12 * hour + dateTime.minute / 60 * 30;
    Offset hourHand1 = pointOffset(radius, radius * 0.1, angle + 180);
    Offset hourHand2 = pointOffset(radius, radius * 0.45, angle);
    canvas.drawLine(hourHand1, hourHand2, hourPaint);
  }

  ///绘制分针
  void drawMinute(Canvas canvas) {
    final minute = dateTime.minute;
    double angle = 360 / 60 * minute + dateTime.second / 60 * 6;
    Offset minuteHand1 = pointOffset(radius, radius * 0.1, angle + 180);
    Offset minuteHand2 = pointOffset(radius, radius * 0.7, angle);
    canvas.drawLine(minuteHand1, minuteHand2, minutePaint);
  }

  ///绘制秒针
  void drawSecond(Canvas canvas) {
    final second = dateTime.second;
    double angle = 360 / 60 * second;
    Offset secondHand1 = pointOffset(radius, radius * 0.1, angle + 180);
    Offset secondHand2 = pointOffset(radius, radius * 0.7, angle);
    canvas.drawLine(secondHand1, secondHand2, secondPaint);
  }

  ///绘制中间圆圈
  void drawMiddleCircle(Canvas canvas) {
    canvas.drawCircle(Offset(radius, radius), middleCircleWidth, centerPaint);
  }

  ///绘制移动小球
  void drawMoveBall(Canvas canvas) {
    final second = dateTime.second;
    canvas.drawCircle(scaleOffset[second], middleCircleWidth, moveBallPaint);
  }
}

///创建Paint
Paint createPaint(Color color, double strokeWidth,
    {PaintingStyle style = PaintingStyle.fill}) {
  return Paint()
    ..color = color
    ..isAntiAlias = true
    ..style = style
    ..strokeCap = StrokeCap.round
    ..strokeWidth = strokeWidth;
}

///圆中万能求点公式
Offset pointOffset(double radius, double l, double angle) {
  return Offset(
    radius + l * sin(degToRad(angle)),
    radius - l * cos(degToRad(angle)),
  );
}

///角度转换为弧度
num degToRad(num deg) => deg * (pi / 180.0);

github链接：https://github.com/yixiaolunhui/flutter_clock