Flutter仿真翻页效果

import 'package:flutter/material.dart';
import 'book_painter.dart';import 'cal_point.dart';
class BookPage extends StatefulWidget {  @override  _BookPageState createState() => _BookPageState();}
class _BookPageState extends State<BookPage>    with SingleTickerProviderStateMixin {  CalPoint curPoint = CalPoint.data(-1, -1);  CalPoint prePoint = CalPoint.data(-1, -1);
  PositionStyle style = PositionStyle.STYLE_LOWER_RIGHT;  double width;  double height;  AnimationController animationController;  Animation cancelAnim;  Tween cancelValue;  bool needCancelAnim = true;
  toNormal([_]) {    if (needCancelAnim) {      startCancelAnim();    } else {      setState(() {        style = PositionStyle.STYLE_LOWER_RIGHT;        prePoint = CalPoint.data(-1, -1);        curPoint = CalPoint.data(-1, -1);      });    }  }
  toDragUpdate(d) {    var x = d.localPosition.dx;    var y = d.localPosition.dy;    setState(() {      curPoint = CalPoint.data(x, y);    });  }
  toDown(TapDownDetails d) {    prePoint = CalPoint.data(-1, -1);    var dy = d.localPosition.dy;    var dx = d.localPosition.dx;
    if (dx <= width / 3) {      //左      style = PositionStyle.STYLE_LEFT;    } else if (dx > width / 3 && dy <= height / 3) {      //上      style = PositionStyle.STYLE_TOP_RIGHT;    } else if (dx > width * 2 / 3 && dy > height / 3 && dy <= height * 2 / 3) {      //右      style = PositionStyle.STYLE_RIGHT;    } else if (dx > width / 3 && dy > height * 2 / 3) {      //下      style = PositionStyle.STYLE_LOWER_RIGHT;    } else if (dx > width / 3 &&        dx < width * 2 / 3 &&        dy > height / 3 &&        dy < height * 2 / 3) {      //中      style = PositionStyle.STYLE_MIDDLE;    }
    var x = d.localPosition.dx;    var y = d.localPosition.dy;    setState(() {      curPoint = CalPoint.data(x, y);    });  }
  startCancelAnim() {    double dx, dy;    if (style == PositionStyle.STYLE_TOP_RIGHT) {      dx = (width - 1 - prePoint.x);      dy = (1 - prePoint.y);    } else if (style == PositionStyle.STYLE_LOWER_RIGHT) {      dx = (width - 1 - prePoint.x);      dy = (height - 1 - prePoint.y);    } else {      dx = prePoint.x - width;      dy = -prePoint.y;    }    cancelValue =        Tween(begin: Offset(prePoint.x, prePoint.y), end: Offset(dx, dy));    animationController.forward();  }
  _initCancelAnim() {    animationController = new AnimationController(        vsync: this, duration: Duration(milliseconds: 300));    cancelAnim = animationController.drive(CurveTween(curve: Curves.linear));    cancelAnim      ..addListener(() {        if (animationController.isAnimating) {          setState(() {            var bdx = cancelValue.begin.dx;            var bdy = cancelValue.begin.dy;
            var edx = cancelValue.end.dx;            var edy = cancelValue.end.dy;
            curPoint = CalPoint.data(                bdx + edx * cancelAnim.value, bdy + edy * cancelAnim.value);          });        }      })      ..addStatusListener((status) {        if (status == AnimationStatus.completed) {          print("object");          setState(() {            style = PositionStyle.STYLE_LOWER_RIGHT;            prePoint = CalPoint.data(-1, -1);            curPoint = CalPoint.data(-1, -1);            animationController.reset();          });        }      });  }
  @override  void initState() {    super.initState();    _initCancelAnim();  }
  @override  Widget build(BuildContext context) {    width = MediaQuery.of(context).size.width;    height = MediaQuery.of(context).size.height - kToolbarHeight;    Color bgColor = Colors.tealAccent;    return Scaffold(      appBar: AppBar(        title: new Text("BookPage"),      ),      body: Container(        height: height,        width: width,        child: GestureDetector(          onTapDown: toDown,          onTapUp: toNormal,          onPanEnd: (detail) {            // needCancelAnim = false;            // if (IsRight) {            //   needCancelAnim = false;            // } else {            //   needCancelAnim = true;            // }            toNormal();          },          onPanCancel: toNormal,          onPanUpdate: (detail) {            toDragUpdate(detail);          },          child: CustomPaint(            painter: BookPainter(              text: content,              text2: content2,              viewWidth: width,              viewHeight: height,              cur: curPoint,              pre: prePoint,              style: style,              bgColor: bgColor,              frontColor: Colors.yellow,              limitAngle: true,              changedPoint: (pre) {                prePoint = pre;              },            ),          ),        ),      ),    );  }}
const content = """林语堂\n一、腰有十文钱必振衣作响；\n二、每与人言必谈及贵戚；\n三、遇美人必急索登床；\n四、见到问路之人必作傲睨之态；\n五、与朋友相聚便喋喋高吟其酸腐诗文；\n六、头已花白却喜唱艳曲；\n七、施人一小惠便广布于众；\n八、与人交谈便借刁言以逞才；\n九、借人之债时其脸如丐，被人索偿时则其态如王；\n十、见人常多蜜语而背地却常揭人短处。""";
const content2 = """林语堂\n1.人本过客来无处，休说故里在何方。随遇而安无不可，人间到处有芳香。——林语堂\n2.人生不过如此，且行且珍惜。自己永远是自己的主角，不要总在别人的戏剧里充当着配角。——林语堂《人生不过如此》\n3.最明亮时总是最迷茫，最繁华时也是最悲凉。——林语堂《京华烟云》\n4.理想的人并不是完美的人，通常只是受人喜爱，并且通情达理的人，而我只是努力去接近于此罢了。——林语堂""";

import 'package:flutter/material.dart';import 'dart:ui' as ui;import 'cal_point.dart';import 'dart:math' as Math;
///触摸类型enum PositionStyle {  STYLE_TOP_RIGHT,  STYLE_LOWER_RIGHT,  STYLE_LEFT,  STYLE_RIGHT,  STYLE_MIDDLE,}
///页面画笔class BookPainter extends CustomPainter {  CalPoint a, f, g, e, h, c, j, b, k, d, i;
  double viewWidth;  double viewHeight;
  ///顶部区域  Path pathA;
  ///折叠出来的区域  Path pathC;
  ///背部区域  Path pathB;
  ///背景画笔  Paint bgPaint;
  ///绘制区域画笔  Paint pathAPaint, pathCPaint, pathBPaint;
  ///触摸点的区域  PositionStyle style;
  ///回调数据外放  ValueChanged changedPoint;
  ///背景色  Color bgColor;
  ///前景色  Color frontColor;
  ///文本一  String text;
  ///文本二  String text2;
  ///A区域左阴影矩形短边长度参考值  double lPathAShadowDis = 0;
  /// A区域右阴影矩形短边长度参考值  double rPathAShadowDis = 0;
  BookPainter({    @required this.text,    @required this.text2,    @required this.viewWidth,    @required this.viewHeight,    @required this.frontColor,    @required this.bgColor,    @required CalPoint cur,    @required CalPoint pre,    @required this.changedPoint,    @required this.style,    bool limitAngle,  }) {    init(cur, pre, limitAngle);  }
  @override  bool shouldRepaint(CustomPainter oldDelegate) => true;
  @override  void paint(Canvas canvas, Size size) {    onDraw(canvas, size);  }
  init(CalPoint cur, CalPoint pre, bool limitAngle) {    ///初始化点    _initPoint();
    ///选择工作模型    _selectCalPoint(cur, pre, limitAngle: limitAngle);
    ///计算    _calcPointsXY(a, f);
    ///初始化    _initPaintAndPath();  }
  _initPoint() {    ///计算起始触摸点    a = CalPoint();
    ///计算的位置起点    f = CalPoint();
    ///其他坐标    g = new CalPoint();    e = new CalPoint();    h = new CalPoint();    c = new CalPoint();    j = new CalPoint();    b = new CalPoint();    k = new CalPoint();    d = new CalPoint();    i = new CalPoint();
    pathB = new Path();    pathA = new Path();    pathC = new Path();  }
  _selectCalPoint(CalPoint cur, CalPoint pre, {bool limitAngle = true}) {    a.x = cur.x;    a.y = cur.y;    doCalAngle() {      CalPoint touchPoint = CalPoint.data(cur.x, cur.y);      if (f.x != null &&          touchPoint.x != null &&          (limitAngle != null && limitAngle)) {        ///如果大于0则设置a点坐标重新计算各标识点位置，否则a点坐标不变        if (_calcPointCX(touchPoint, f) > 0) {          changedPoint?.call(cur);          _calcPointsXY(a, f);        } else {          a.x = pre.x;          a.y = pre.y;          _calcPointsXY(a, f);        }      } else if (_calcPointCX(touchPoint, f) < 0) {        ///如果c点x坐标小于0则重新测量a点坐标        _calcPointAByTouchPoint();        _calcPointsXY(a, f);      } else {        a.x = pre.x;        a.y = pre.y;      }    }
    switch (style) {      case PositionStyle.STYLE_TOP_RIGHT:        f.x = viewWidth;        f.y = 0;        doCalAngle();        break;      case PositionStyle.STYLE_LOWER_RIGHT:        f.x = viewWidth;        f.y = viewHeight;        doCalAngle();        break;      case PositionStyle.STYLE_LEFT:      case PositionStyle.STYLE_RIGHT:      case PositionStyle.STYLE_MIDDLE:        a.y = viewHeight - 1;        f.x = viewWidth;        f.y = viewHeight;        _calcPointsXY(a, f);        break;      default:        break;    }  }
  _initPaintAndPath() {    bgPaint = new Paint();    bgPaint.color = Colors.white;
    pathAPaint = new Paint();    pathAPaint.color = bgColor;    pathAPaint.isAntiAlias = true;
    pathCPaint = new Paint();    pathCPaint.color = frontColor;    pathCPaint.blendMode = BlendMode.dstATop;    pathCPaint.isAntiAlias = true;
    pathBPaint = new Paint();    pathBPaint.color = Colors.tealAccent;    pathBPaint.blendMode = BlendMode.dstATop;    pathBPaint.isAntiAlias = true;
    pathB = new Path();  }
  void onDraw(Canvas canvas, Size size) async {    canvas.saveLayer(Rect.fromLTRB(0, 0, size.width, size.height), bgPaint);
    if (a.x == -1 && a.y == -1) {      _drawPathAWithPic(canvas, _getPathDefault());      _drawPathCWithPic(canvas, _getPathDefault(), pathCPaint);      _drawPathBWithPic(canvas, _getPathDefault());    } else {      if (f.x == viewWidth && f.y == 0) {        _drawPathAWithPic(canvas, _getPathAFromTopRight());        _drawPathCWithPic(canvas, _getPathAFromTopRight(), pathCPaint);        _drawPathBWithPic(canvas, _getPathAFromTopRight());      } else if (f.x == viewWidth && f.y == viewHeight) {        _drawPathAWithPic(canvas, _getPathAFromLowerRight());        _drawPathCWithPic(canvas, _getPathAFromLowerRight(), pathCPaint);        _drawPathBWithPic(canvas, _getPathAFromLowerRight());      }    }
    canvas.restore();  }
  void _drawPathAWithPic(Canvas canvas, Path pp) {    canvas.save();    var pictureRecorder = ui.PictureRecorder();    var canvasBitmap = Canvas(pictureRecorder);    var paint = Paint();    paint.isAntiAlias = true;    canvasBitmap.drawPath(pp, pathAPaint);    _drawText(canvasBitmap, text, Colors.black, viewWidth, Offset.zero);    var pic = pictureRecorder.endRecording();    canvas.clipPath(pp);    canvas.drawPicture(pic);
    if (style == PositionStyle.STYLE_LEFT ||        style == PositionStyle.STYLE_RIGHT) {      _drawPathAHorizontalShadow(canvas, pathA);    } else if (a.x != -1 && a.y != -1) {      _drawPathALeftShadow(canvas, pp);      _drawPathARightShadow(canvas, pp);    }
    canvas.restore();  }
  void _drawPathALeftShadow(Canvas canvas, Path pathA) {    canvas.restore();    canvas.save();
    var gradientColors = [Color(0x01333333), Color(0x33333333)];
    double left;    double right;    double top = e.y;    double bottom = (e.y + viewHeight);
    ui.Gradient gradient;    if (style == PositionStyle.STYLE_TOP_RIGHT) {      left = (e.x - lPathAShadowDis / 2);      right = (e.x);      gradient = ui.Gradient.linear(          Offset(left, top), Offset(right, top), gradientColors);    } else {      left = (e.x);      right = (e.x + lPathAShadowDis / 2);
      gradient = ui.Gradient.linear(          Offset(right, top), Offset(left, top), gradientColors);    }    Paint paint = new Paint()..shader = gradient;
    //裁剪出我们需要的区域    Path mPath = new Path();    mPath.moveTo(a.x - Math.max(rPathAShadowDis, lPathAShadowDis) / 2, a.y);    mPath.lineTo(d.x, d.y);    mPath.lineTo(e.x, e.y);    mPath.lineTo(a.x, a.y);    mPath.close();    //canvas.clipPath(pathA);    var pn = Path.combine(PathOperation.intersect, pathA, mPath);    canvas.clipPath(pn);
    canvas.translate(e.x, e.y);    canvas.rotate(Math.atan2(e.x - a.x, a.y - e.y));    canvas.translate(-e.x, -e.y);    var rect = Rect.fromLTRB(left, top, right, bottom);    canvas.drawRect(rect, paint);  }
  void _drawPathARightShadow(Canvas canvas, Path pathA) {    canvas.restore();    canvas.save();
    var gradientColors = [      Color(0x33333333),      Color(0x01333333),    ];
    double viewDiagonalLength = _hypot(viewWidth, viewHeight); //view对角线长度    double left = h.x;    double right = (h.x + viewDiagonalLength * 10); //需要足够长的长度    double top;    double bottom;
    ui.Gradient gradient;    if (style == PositionStyle.STYLE_TOP_RIGHT) {      top = (h.y - rPathAShadowDis / 2);      bottom = h.y;      gradient = ui.Gradient.linear(          Offset(left, bottom), Offset(left, top), gradientColors);    } else {      top = h.y;      bottom = (h.y + rPathAShadowDis / 2);
      gradient = ui.Gradient.linear(          Offset(left, top), Offset(left, bottom), gradientColors);    }    Paint paint = new Paint()..shader = gradient;
    Path mPath = new Path();    mPath.moveTo(a.x - Math.max(rPathAShadowDis, lPathAShadowDis) / 2, a.y);//        mPath.lineTo(i.x,i.y);    mPath.lineTo(h.x, h.y);    mPath.lineTo(a.x, a.y);    mPath.close();    var pn = Path.combine(PathOperation.intersect, pathA, mPath);    canvas.clipPath(pn);
    canvas.translate(h.x, h.y);    canvas.rotate(Math.atan2(a.y - h.y, a.x - h.x));    canvas.translate(-h.x, -h.y);    var rect = Rect.fromLTRB(left, top, right, bottom);    canvas.drawRect(rect, paint);  }
  void _drawPathAHorizontalShadow(Canvas canvas, Path pathA) {    canvas.restore();    canvas.save();
    var radientColors = [Color(0x01333333), Color(0x44333333)]; //渐变颜色数组
    double maxShadowWidth = 30; //阴影矩形最大的宽度    double left = (a.x - Math.min(maxShadowWidth, (rPathAShadowDis / 2)));    double right = (a.x);    double top = 0;    double bottom = viewHeight;
    ui.Gradient gradient = ui.Gradient.linear(        Offset(left, top), Offset(right, top), radientColors);    Paint paint = new Paint()..shader = gradient;
    canvas.clipPath(pathA);
    canvas.translate(a.x, a.y);    canvas.rotate(Math.atan2(f.x - a.x, f.y - h.y));    canvas.translate(-a.x, -a.y);    var rect = Rect.fromLTRB(left, top, right, bottom);    canvas.drawRect(rect, paint);  }
  void _drawPathBWithPic(Canvas canvas, Path pa) {    canvas.save();    var pictureRecorder = ui.PictureRecorder();    var canvasBitmap = Canvas(pictureRecorder);    var paint = Paint();    paint.isAntiAlias = true;    canvasBitmap.drawPath(_getPathB(), pathBPaint);    _drawText(canvasBitmap, text2, Colors.black, viewWidth, Offset.zero);
    var pic = pictureRecorder.endRecording();    var pn = Path.combine(PathOperation.reverseDifference, pa, _getPathB());    pn = Path.combine(PathOperation.reverseDifference, _getPathC(), pn);    canvas.clipPath(pn);    canvas.drawPicture(pic);    _drawPathBShadow(canvas); //调用阴影绘制方法    canvas.restore();  }
  void _drawPathBShadow(Canvas canvas) {    var gradientColors = [Color(0xf0111111), Color(0x00000000)]; //渐变颜色数组    int elevation = 6;    int deepOffset = 0; //深色端的偏移值    int lightOffset = 0; //浅色端的偏移值    double aTof = _hypot((a.x - f.x), (a.y - f.y)); //a到f的距离    double viewDiagonalLength = _hypot(viewWidth, viewHeight); //对角线长度
    double left;    double right;    double top = c.y;    double bottom = (viewDiagonalLength + c.y);    ui.Gradient gradient;    if (style == PositionStyle.STYLE_TOP_RIGHT) {      //f点在右上角      //从左向右线性渐变      left = (c.x - deepOffset); //c点位于左上角      right = (c.x + aTof / elevation + lightOffset);
      gradient = ui.Gradient.linear(          Offset(left, top), Offset(right, top), gradientColors);    } else {      left = (c.x - aTof / elevation - lightOffset); //c点位于左下角      right = (c.x + deepOffset);      gradient = ui.Gradient.linear(          Offset(right, top), Offset(left, top), gradientColors);    }
    Paint paint = new Paint()      //..color = Colors.black.withAlpha(80);      //..blendMode = BlendMode.srcOver      ..shader = gradient;
    canvas.translate(c.x, c.y);    canvas.rotate(Math.atan2(e.x - f.x, h.y - f.y));    canvas.translate(-c.x, -c.y);    var rect = Rect.fromLTRB(left, top, right, bottom);    canvas.drawRect(rect, paint);  }
  void _drawPathCWithPic(Canvas canvas, Path pathA, Paint pathPaint) {    canvas.drawPath(_getPathC(), pathPaint);
    canvas.save();    var pictureRecorder = ui.PictureRecorder();    var canvasBitmap = Canvas(pictureRecorder);    canvasBitmap.drawPath(_getPathB(), pathPaint);    var pic = pictureRecorder.endRecording();
    var pn = Path.combine(PathOperation.reverseDifference, pathA, _getPathC());    canvas.clipPath(pn);
    double eh = _hypot(f.x - e.x, h.y - f.y);    double sin0 = (f.x - e.x) / eh;    double cos0 = (h.y - f.y) / eh;    //设置翻转和旋转矩阵    var mMatrixArray = [      0.0,      0.0,      0.0,      0.0,      0.0,      0.0,      0.0,      0.0,      0.0,      0.0,      0.1,      0.0,      0.0,      0.0,      0.0,      0.1    ];    mMatrixArray[0] = -(1 - 2 * sin0 * sin0);    mMatrixArray[1] = 2 * sin0 * cos0;    mMatrixArray[4] = 2 * sin0 * cos0;    mMatrixArray[5] = 1 - 2 * sin0 * sin0;
    Matrix4 mMatrix = Matrix4.fromList(mMatrixArray);
    mMatrix.leftTranslate(e.x, e.y);    mMatrix.translate(-e.x, -e.y);    canvas.transform(mMatrix.storage);    canvas.drawPicture(pic);    _drawPathCShadow(canvas); //调用阴影绘制方法    canvas.restore();  }
  void _drawPathCShadow(Canvas canvas) {    var gradientColors = [Color(0x00333333), Color(0xff111111)]; //渐变颜色数组
    int deepOffset = 1; //深色端的偏移值    int lightOffset = -30; //浅色端的偏移值    var viewDiagonalLength = _hypot(viewWidth, viewHeight); //view对角线长度    double midpointCe = (c.x + e.x) / 2; //ce中点    double midpointJh = (j.y + h.y) / 2; //jh中点    double minDisToControlPoint = Math.min(        (midpointCe - e.x).abs(), (midpointJh - h.y).abs()); //中点到控制点的最小值
    double left;    double right;    double top = c.y;    double bottom = (viewDiagonalLength + c.y);    ui.Gradient gradient;    if (style == PositionStyle.STYLE_TOP_RIGHT) {      left = (c.x - lightOffset);      right = (c.x + minDisToControlPoint + deepOffset);
      gradient = ui.Gradient.linear(          Offset(left, top), Offset(right, top), gradientColors);    } else {      left = (c.x - minDisToControlPoint - deepOffset);      right = (c.x + lightOffset);      gradient = ui.Gradient.linear(          Offset(right, top), Offset(left, top), gradientColors);    }    Paint paint = new Paint()..shader = gradient;
    canvas.translate(c.x, c.y);    canvas.rotate(Math.atan2(e.x - f.x, h.y - f.y));    canvas.translate(-c.x, -c.y);    var rect = Rect.fromLTRB(left, top, right, bottom);    canvas.drawRect(rect, paint);  }
  /// 计算各点坐标  void _calcPointsXY(CalPoint a, CalPoint f) {    g.x = (a.x + f.x) / 2;    g.y = (a.y + f.y) / 2;
    e.x = g.x - (f.y - g.y) * (f.y - g.y) / (f.x - g.x);    e.y = f.y;
    h.x = f.x;    h.y = g.y - (f.x - g.x) * (f.x - g.x) / (f.y - g.y);
    c.x = e.x - (f.x - e.x) / 2;    c.y = f.y;
    j.x = f.x;    j.y = h.y - (f.y - h.y) / 2;
    b = _getInterPoint(a, e, c, j);    k = _getInterPoint(a, h, c, j);
    d.x = (c.x + 2 * e.x + b.x) / 4;    d.y = (2 * e.y + c.y + b.y) / 4;
    i.x = (j.x + 2 * h.x + k.x) / 4;    i.y = (2 * h.y + j.y + k.y) / 4;
    double lA = a.y - e.y;    double lB = e.x - a.x;    double lC = a.x * e.y - e.x * a.y;    lPathAShadowDis = ((lA * d.x + lB * d.y + lC) / (_hypot(lA, lB)).abs());
    double rA = a.y - h.y;    double rB = h.x - a.x;    double rC = a.x * h.y - h.x * a.y;    rPathAShadowDis = ((rA * i.x + rB * i.y + rC) / _hypot(rA, rB)).abs();  }
  /// 计算两线段相交点坐标  CalPoint _getInterPoint(      CalPoint lineOneToPointOne,      CalPoint lineOneToPointTwo,      CalPoint lineTwoToPointOne,      CalPoint lineTwoToPointTwo) {    double x1, y1, x2, y2, x3, y3, x4, y4;    x1 = lineOneToPointOne.x;    y1 = lineOneToPointOne.y;    x2 = lineOneToPointTwo.x;    y2 = lineOneToPointTwo.y;    x3 = lineTwoToPointOne.x;    y3 = lineTwoToPointOne.y;    x4 = lineTwoToPointTwo.x;    y4 = lineTwoToPointTwo.y;
    double pointX =        ((x1 - x2) * (x3 * y4 - x4 * y3) - (x3 - x4) * (x1 * y2 - x2 * y1)) /            ((x3 - x4) * (y1 - y2) - (x1 - x2) * (y3 - y4));    double pointY =        ((y1 - y2) * (x3 * y4 - x4 * y3) - (x1 * y2 - x2 * y1) * (y3 - y4)) /            ((y1 - y2) * (x3 - x4) - (x1 - x2) * (y3 - y4));
    return CalPoint.data(pointX, pointY);  }
  ///获取f点在右下角的pathA  Path _getPathAFromLowerRight() {    pathA.reset();    pathA.lineTo(0, viewHeight); //移动到左下角    pathA.lineTo(c.x, c.y); //移动到c点    pathA.quadraticBezierTo(e.x, e.y, b.x, b.y); //从c到b画贝塞尔曲线，控制点为e    pathA.lineTo(a.x, a.y); //移动到a点    pathA.lineTo(k.x, k.y); //移动到k点    pathA.quadraticBezierTo(h.x, h.y, j.x, j.y); //从k到j画贝塞尔曲线，控制点为h    pathA.lineTo(viewWidth, 0); //移动到右上角    pathA.close(); //闭合区域    return pathA;  }
  ///获取f点在右上角的pathA  Path _getPathAFromTopRight() {    pathA.reset();    pathA.lineTo(c.x, c.y); //移动到c点    pathA.quadraticBezierTo(e.x, e.y, b.x, b.y); //从c到b画贝塞尔曲线，控制点为e    pathA.lineTo(a.x, a.y); //移动到a点    pathA.lineTo(k.x, k.y); //移动到k点    pathA.quadraticBezierTo(h.x, h.y, j.x, j.y); //从k到j画贝塞尔曲线，控制点为h    pathA.lineTo(viewWidth, viewHeight); //移动到右下角    pathA.lineTo(0, viewHeight); //移动到左下角    pathA.close();    return pathA;  }
  ///翻页折角区域  Path _getPathC() {    pathC.reset();    pathC.moveTo(i.x, i.y); //移动到i点    pathC.lineTo(d.x, d.y); //移动到d点    pathC.lineTo(b.x, b.y); //移动到b点    pathC.lineTo(a.x, a.y); //移动到a点    pathC.lineTo(k.x, k.y); //移动到k点    pathC.close(); //闭合区域    return pathC;  }
  ///翻页后剩余区域  Path _getPathB() {    pathB.reset();    pathB.lineTo(0, viewHeight); //移动到左下角    pathB.lineTo(viewWidth, viewHeight); //移动到右下角    pathB.lineTo(viewWidth, 0); //移动到右上角    pathB.close(); //闭合区域    return pathB;  }
  ///绘制默认的界面  Path _getPathDefault() {    pathA.reset();    pathA.lineTo(0, viewHeight);    pathA.lineTo(viewWidth, viewHeight);    pathA.lineTo(viewWidth, 0);    pathA.close();    return pathA;  }
  ///计算C点的X值  _calcPointCX(CalPoint a, CalPoint f) {    CalPoint g, e;    g = new CalPoint();    e = new CalPoint();    g.x = (a.x + f.x) / 2;    g.y = (a.y + f.y) / 2;
    e.x = g.x - (f.y - g.y) * (f.y - g.y) / (f.x - g.x);    e.y = f.y;
    return e.x - (f.x - e.x) / 2;  }
  ///如果c点x坐标小于0,根据触摸点重新测量a点坐标  _calcPointAByTouchPoint() {    double w0 = viewWidth - c.x;
    double w1 = (f.x - a.x).abs();    double w2 = viewWidth * w1 / w0;    a.x = (f.x - w2).abs();
    double h1 = (f.y - a.y).abs();    double h2 = w2 * h1 / w1;    a.y = (f.y - h2).abs();  }
  ///利用 Paragraph 实现 _drawText  _drawText(      Canvas canvas, String text, Color color, double width, Offset offset,      {TextAlign textAlign = TextAlign.start, double fontSize}) {    ui.ParagraphBuilder pb = ui.ParagraphBuilder(ui.ParagraphStyle(      textAlign: textAlign,      fontSize: fontSize,    ));    pb.pushStyle(ui.TextStyle(color: color));    pb.addText(text);    ui.ParagraphConstraints pc = ui.ParagraphConstraints(width: width);
    ///这里需要先layout, 后面才能获取到文字高度    ui.Paragraph paragraph = pb.build()..layout(pc);    canvas.drawParagraph(paragraph, offset);  }
  //_drawTestPoint() {//    _drawText(canvas, "a",  Colors.red, size.width, Offset(a.x, a.y),//        textAlign: TextAlign.left, fontSize: 25);//    _drawText(canvas, "f",  Colors.red, size.width, Offset(f.x, f.y),//        textAlign: TextAlign.left, fontSize: 25);//    _drawText(canvas, "g",  Colors.red, size.width, Offset(g.x, g.y),//        textAlign: TextAlign.left, fontSize: 25);////    _drawText(canvas, "e",  Colors.red, size.width, Offset(e.x, e.y),//        textAlign: TextAlign.left, fontSize: 25);//    _drawText(canvas, "h",  Colors.red, size.width, Offset(h.x, h.y),//        textAlign: TextAlign.left, fontSize: 25);////    _drawText(canvas, "c",  Colors.red, size.width, Offset(c.x, c.y),//        textAlign: TextAlign.left, fontSize: 25);//    _drawText(canvas, "j",  Colors.red, size.width, Offset(j.x, j.y),//        textAlign: TextAlign.left, fontSize: 25);////    _drawText(canvas, "b",  Colors.red, size.width, Offset(b.x, b.y),//        textAlign: TextAlign.left, fontSize: 25);//    _drawText(canvas, "k",  Colors.red, size.width, Offset(k.x, k.y),//        textAlign: TextAlign.left, fontSize: 25);////    _drawText(canvas, "d",  Colors.red, size.width, Offset(d.x, d.y),//        textAlign: TextAlign.left, fontSize: 25);//    _drawText(canvas, "i",  Colors.red, size.width, Offset(i.x, i.y),//        textAlign: TextAlign.left, fontSize: 25);  // }
  num _hypot(num x, num y) {    var first = x.abs();    var second = y.abs();
    if (y > x) {      first = y.abs();      second = x.abs();    }
    if (first == 0.0) {      return second;    }
    final t = second / first;    return first * Math.sqrt(1 + t * t);  }}

import 'package:flutter/material.dart';
class BookTextClip extends CustomClipper<Path> {  final Path path;
  BookTextClip(this.path);
  @override  Path getClip(Size size) {    return path;  }
  @override  bool shouldReclip(CustomClipper<Path> oldClipper) {    return true;  }}

class CalPoint {  CalPoint();
  CalPoint.data(this.x, this.y);
  double x = -1;  double y = -1;}