【Flutter高级玩法-shape】Path在手，天下我有

张风捷特烈

发布于 2020-04-30 17:43:22

3.8K0

发布于 2020-04-30 17:43:22

文章被收录于专栏：Android知识点总结

不知你注意或是没注意组件的shape属性，可能你觉得没啥用，或说一带而过，今天就来掰扯一下这个ShapeBorder 对象它的强大远远超出你的想象，不过记住: Path 在手，天下我有，先看下效果

Material
Card
FloatingActionButton
RawMaterialButton
MaterialButton
    |----FlatButton
    |----RaisedButton
    |----OutlineButton
...

ClipPath

一、`shape`属性对应的几类对象

shape 对应 ShapeBorder 对象 , 它的子类如下:

ShapeBorder [abstract]
|---BoxBorder [abstract]
    |---BorderDirectional
    |---Border
|---RoundedRectangleBorder
|---ContinuousRectangleBorder
|---CircleBorder
|---InputBorder [abstract]
    |---OutlineInputBorder
    |---UnderlineInputBorder

1.从Material组件开始说起

估计这个组件用的人不多，但是翻看一下源码Card,RawMaterialButton及子族它们的shape属性都来自于Material组件,可以说是它是shape的本宗，所以擒贼先擒王 下面是一个Material组件基本使用的demo:

  Widget _buildNoShape() {
    return Material(
              color: Colors.orangeAccent,
              elevation: 10,
              child: Container(
                alignment: Alignment.center,
                padding: EdgeInsets.all(10),
                height: 80,
                child: Text(
                  "No Shape",
                  style: TextStyle(color: Colors.white, fontSize: 20),
                ),
              ),
            );
  }
复制代码

2 `BoxBorder$BorderDirectional 与 BoxBorder$Border`

BoxBorder主要掌管边线方面的事，自身是abstract，不能直接用 BorderDirectional 通过 【top】【bottom】【start】【end】分别控制上下左右的边线边线对象BorderSide

Widget _buildBorderDirectional() {
  return Material(
            color: Colors.orangeAccent,
            shape: BorderDirectional(
                top: BorderSide(
                  color: Colors.white,
                ),
                start: BorderSide(
                  color: Colors.black,
                  width: 15
                ),
              bottom: BorderSide(
                color: Colors.white,
              )
            ),
            elevation: 2,
            child: Container(
              alignment: Alignment.center,
              padding: EdgeInsets.all(10),
              height: 80,
              child: Text(
                "BorderDirectional",
                style: TextStyle(color: Colors.white, fontSize: 20),
              ),
            ),
          );
}
复制代码

Border 通过 【top】【bottom】【left】【right】分别控制上下左右的边线本质上和BorderDirectional并没有什么区别

Widget _buildBorder() {
  return Material(
    color: Colors.orangeAccent,
    shape: Border(
      top: BorderSide(width: 5.0, color: Color(0xFFFFDFDFDF)),
      left: BorderSide(width: 5.0, color: Color(0xFFFFDFDFDF)),
      right: BorderSide(width: 5.0, color: Color(0xFFFF7F7F7F)),
      bottom: BorderSide(width: 5.0, color: Color(0xFFFF7F7F7F)),
    ),
    elevation: 10,
    child: Container(
      alignment: Alignment.center,
      padding: EdgeInsets.all(10),
      height: 80,
      child: Text(
        "Border",
        style: TextStyle(color: Colors.white, fontSize: 20),
      ),
    ),
  );
}
复制代码

3 `CircleBorder`

CircleBorder 会以min(with,height) 为直径，裁处一个圆形

Widget _buildCircleBorder() {
  return Material(
    color: Colors.orangeAccent,
    shape: CircleBorder(
      side: BorderSide(width: 2.0, color: Color(0xFFFFDFDFDF)),
    ),
    elevation: 2,
    child: Container(
      alignment: Alignment.center,
      padding: EdgeInsets.all(10),
      height: 80,
      child: Text(
        "Circle",
        style: TextStyle(color: Colors.white, fontSize: 20),
      ),
    ),
  );
}
复制代码

4 `RoundedRectangleBorder`和`ContinuousRectangleBorder`

圆角类矩形

Widget _buildRoundedRectangleBorder() {
  return Material(
    color: Colors.orangeAccent,
    shape: RoundedRectangleBorder(
        side: BorderSide(width: 1.0, color: Colors.black),
        borderRadius: BorderRadius.all(Radius.circular(15))),
    elevation: 2,
    child: Container(
      alignment: Alignment.center,
      padding: EdgeInsets.all(10),
      height: 80,
      child: Text(
        "RoundedRectangleBorder",
        style: TextStyle(color: Colors.white, fontSize: 20),
      ),
    ),
  );
}
复制代码

Material _buildContinuousRectangleBorder() {
  return Material(
    color: Colors.orangeAccent,
    elevation: 2,
    shape: ContinuousRectangleBorder(
      side: BorderSide.none,
      borderRadius: BorderRadius.circular(40.0),
    ),
    child: Container(
      alignment: Alignment.center,
      padding: EdgeInsets.all(10),
      height: 80,
      child: Text(
        "ContinuousRectangleBorder",
        style: TextStyle(color: Colors.white, fontSize: 20),
      ),
    ),
  );
}
复制代码

5 `OutlineInputBorder`和`UnderlineInputBorder`

常用与输入框的边线

Material _buildOutlineInputBorder() {
  return Material(
    color: Colors.orangeAccent,
    elevation: 2,
    shape: OutlineInputBorder(
      borderSide: BorderSide(width: 2.0, color: Colors.purple),
      borderRadius: BorderRadius.circular(20.0),
    ),
    child: Container(
      alignment: Alignment.center,
      padding: EdgeInsets.all(10),
      height: 80,
      child: Text(
        "OutlineInputBorder",
        style: TextStyle(color: Colors.white, fontSize: 20),
      ),
    ),
  );
}

Material _buildUnderlineInputBorder() {
  return Material(
    color: Colors.orangeAccent,
    elevation: 2,
    shape: UnderlineInputBorder(
      borderSide: BorderSide(width: 5.0, color: Colors.blue),
      borderRadius: BorderRadius.circular(20),
    ),
    child: Container(
      alignment: Alignment.center,
      padding: EdgeInsets.all(10),
      height: 80,
      child: Text(
        "UnderlineInputBorder",
        style: TextStyle(color: Colors.white, fontSize: 20),
      ),
    ),
  );
}
复制代码

这样Flutter内置的形状就over了，好了，引言结束，下面开始正题。

二、自定义ShapeBorder

1.继承ShapeBorder

一共有五个抽象方法

class SimpleShapeBoder extends ShapeBorder{
  @override
  EdgeInsetsGeometry get dimensions => null;

  @override
  Path getInnerPath(Rect rect, {TextDirection textDirection}) {
    return null;
  }

  @override
  Path getOuterPath(Rect rect, {TextDirection textDirection}) {
    return null;
  }

  @override
  void paint(Canvas canvas, Rect rect, {TextDirection textDirection}) {
  }

  @override
  ShapeBorder scale(double t) {
    return null;
  }
  
}

2. paint方法

看到paint中的Canvas对象，心想: 又到装13的机会了 先瞄一眼这个rect对象的信息:

@override
void paint(Canvas canvas, Rect rect, {TextDirection textDirection}) {
  print(rect.toString());
}

I/flutter ( 8697): Rect.fromLTRB(0.0, 0.0, 395.4, 80.0) 表明可以直接拿到组件的区域，然后....为所欲为吧

先画个小圆以表敬意: 这表示你可以通过shape属性来在一个组件上画任意的东西如果有耐心画幅清明上河图也不成问题。paint是不是非常强大？

  @override
  void paint(Canvas canvas, Rect rect, {TextDirection textDirection}) {
    var paint = Paint()
      ..color = Colors.white
      ..strokeWidth = 2.0
      ..style = PaintingStyle.stroke
      ..strokeJoin = StrokeJoin.round;
    var w = rect.width;
    var h = rect.height;
    canvas.drawCircle(Offset(0.3*h,0.23*h), 0.12*h, paint);
    canvas.drawCircle(Offset(0.3*h,0.23*h), 0.06*h, paint..style=PaintingStyle.fill..color=Colors.black);
  }

getOuterPath 返回一个Path对象，也就是形状的裁剪，这个更厉害先来看圆角怎么切: 用path.addRRect来添加一个圆角矩形，然后就出现效果了

  @override
  Path getOuterPath(Rect rect, {TextDirection textDirection}) {
    var path = Path();
    path.addRRect(RRect.fromRectAndRadius(rect, Radius.circular(10)));
    return path;
  }

3. `getOuterPath方法`

来打个洞吧。下面根据位置计算出一个圆形路径将圆角矩形和圆形两个路径叠加，最后使用奇偶环绕来处理路径

关于路径Path的环绕规则已经其他的东西，可以看以前写的Android的路径文章 Android关于Path你所知道的和不知道的一切-填充的环绕原则

@override
Path getOuterPath(Rect rect, {TextDirection textDirection}) {
  var path = Path();
  path.addRRect(RRect.fromRectAndRadius(rect, Radius.circular(10)));
  
  var w = rect.width;
  var h = rect.height;
  var radius = 0.2*h;
  var pl= 0.1*h;
  var pt= 0.1*h;
  var left = w - radius - pl;
  var top = pt;
  var right = left + radius;
  var bottom = top + radius;
  path.addOval(Rect.fromLTRB(left, top, right, bottom));
  path.fillType = PathFillType.evenOdd;
  
  return path;
}

就此来封装一个打洞的形状HoleShapeBorder，可指定洞的大小和偏移分率这样洞在组件之间就可以随意移动

import 'package:flutter/material.dart';

/// create by 张风捷特烈 on 2020-03-06
/// contact me by email 1981462002@qq.com
/// 说明: 打个洞
/// offset 洞的偏移量分率 x,y 在 0~1 之间
/// size 洞的大小

class HoleShapeBorder extends ShapeBorder {
  final Offset offset;
  final double size;


  HoleShapeBorder({this.offset=const Offset(0.1, 0.1), this.size=20});

  @override
  EdgeInsetsGeometry get dimensions => null;

  @override
  Path getInnerPath(Rect rect, {TextDirection textDirection}) {
    var path = Path();
    path.addRRect(RRect.fromRectAndRadius(rect, Radius.circular(5)));
    return path;
  }

  @override
  Path getOuterPath(Rect rect, {TextDirection textDirection}) {
    var path = Path();
    path.addRRect(RRect.fromRectAndRadius(rect, Radius.circular(10)));


    var w = rect.width;
    var h = rect.height;
    var offsetXY = Offset( offset.dx*w,offset.dy*h);
    var d = size;
    _getHold(path, 1, d, offsetXY);
    path.fillType = PathFillType.evenOdd;
    return path;
  }

  _getHold(Path path, int count, double d, Offset offset) {
      var left = offset.dx;
      var top = offset.dy;
      var right = left + d;
      var bottom = top + d;
      path.addOval(Rect.fromLTRB(left, top, right, bottom));
    }

  @override
  void paint(Canvas canvas, Rect rect, {TextDirection textDirection}) {
  }

  @override
  ShapeBorder scale(double t) {
    // TODO: implement scale
    return null;
  }
}

  Material _buildHoleShapeBorder() {
    return Material(
      color: Colors.orangeAccent,
      shape: HoleShapeBorder(
        size: 20,
        offset: Offset(0.05,0.1)
      ),
     //英雄所见...
  }
复制代码

既然能打一个洞，那也可以多打几个洞把相关的属性抽离一下，做的打洞ShapeBorder岂不更香

  @override
  Path getOuterPath(Rect rect, {TextDirection textDirection}) {
    var path = Path();
    path.addRRect(RRect.fromRectAndRadius(rect, Radius.circular(10)));
    var w = rect.width;
    var h = rect.height;
    var holeCount = 12;
    var d = w / (1 + 2 * holeCount);
    _getHold(path, holeCount, d, 8);
    path.fillType = PathFillType.evenOdd;
    return path;
  }

  _getHold(Path path, int count, double d, double pt) {
    for (int i = 0; i < count; i++) {
      var left = d + 2 * d * i;
      var top = pt;
      var right = left + d;
      var bottom = top + d;
      path.addOval(Rect.fromLTRB(left, top, right, bottom));
    }
  }

3.手撕优惠券

群里有个哥们提了一句,看能不能做一个优惠券:

Path在手，就是可以为所欲为，废话不多说，开搞核心方法和上面类似，但涉及到路径操作还有些注意点通过洞的个数和宽度来确定洞的直径，这样会避免最边上的尴尬，适配性更加
lineRate 来确定白线的分率位置(0,1) 下面两幅分别是0.718和0.618

dash 是否是虚线,color 为线的颜色

适应宽高: 分率线和小圆半径都会根据宽高自动进行更改

class CouponShapeBorder extends ShapeBorder {
  final int holeCount;
  final double lineRate;
  final bool dash;
  final Color color;

  CouponShapeBorder(
      {this.holeCount = 6,
      this.lineRate = 0.718,
      this.dash = true,
      this.color = Colors.white});

  @override
  EdgeInsetsGeometry get dimensions => null;

  @override
  Path getInnerPath(Rect rect, {TextDirection textDirection}) {
    return null;
  }

  @override
  Path getOuterPath(Rect rect, {TextDirection textDirection}) {
    var w = rect.width;
    var h = rect.height;

    var d = h / (1 + 2 * holeCount);

    var path = Path();
    path.addRect(rect);

    _formHoldLeft(path, d);
    _formHoldRight(path, w, d);
    _formHoleTop(path, rect);
    _formHoleBottom(path, rect);
    path.fillType = PathFillType.evenOdd;

    return path;
  }

  void _formHoleBottom(Path path, Rect rect) {
    path.addArc(
        Rect.fromCenter(
            center: Offset(lineRate * rect.width, rect.height),
            width: 13.0,
            height: 13.0),
        pi,
        pi);
  }

  void _formHoleTop(Path path, Rect rect) {
    path.addArc(
        Rect.fromCenter(
            center: Offset(lineRate * rect.width, 0),
            width: 13.0,
            height: 13.0),
        0,
        pi);
  }

  _formHoldLeft(Path path, double d) {
    for (int i = 0; i < holeCount; i++) {
      var left = -d / 2;
      var top = 0.0 + d + 2 * d * (i);
      var right = left + d;
      var bottom = top + d;
      path.addArc(Rect.fromLTRB(left, top, right, bottom), -pi / 2, pi);
    }
  }

  _formHoldRight(Path path, double w, double d) {
    for (int i = 0; i < holeCount; i++) {
      var left = -d / 2 + w;
      var top = 0.0 + d + 2 * d * (i);
      var right = left + d;
      var bottom = top + d;
      path.addArc(Rect.fromLTRB(left, top, right, bottom), pi / 2, pi);
    }
  }

  @override
  void paint(Canvas canvas, Rect rect, {TextDirection textDirection}) {
    var paint = Paint()
      ..color = color
      ..strokeWidth = 1.5
      ..style = PaintingStyle.stroke
      ..strokeJoin = StrokeJoin.round;
    var d = rect.height / (1 + 2 * holeCount);
    if (dash) {
      _drawDashLine(canvas, Offset(lineRate * rect.width, d / 2),
          rect.height / 16, rect.height - 13, paint);
    } else {
      canvas.drawLine(Offset(lineRate * rect.width, d / 2),
          Offset(lineRate * rect.width, rect.height - d / 2), paint);
    }
  }

  _drawDashLine(
      Canvas canvas, Offset start, double count, double length, Paint paint) {
    var step = length / count / 2;
    for (int i = 0; i < count; i++) {
      var offset = start + Offset(0, 2 * step * i);
      canvas.drawLine(offset, offset + Offset(0, step), paint);
    }
  }

  @override
  ShapeBorder scale(double t) {
    // TODO: implement scale
    return null;
  }
}

三、ClipPath、Card 万物皆可裁剪

1. ClipPath中使用shape

上面主要在Material中使用，ClipPath中也有ShapeBorder的用武之地现在我想用优惠券的裁切路径来裁个图片，so easy

  Widget _buildClipPath() {
    return Container(
      width: 300,
      height: 200,
      child: ClipPath(
        clipper: ShapeBorderClipper(
          shape: CouponShapeBorder()
        ),
        child: Image.asset('assets/images/bg.jpeg',fit: BoxFit.cover,),

      ),
    );
  }
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2. Card中使用shape

Card是基于Material实现的，可以直接使用shape属性比如下面的列表题目，可以通过边线来润色一下

没形状	有形状

这篇就到这里吧，只是为你打开了一扇大门，究其核心还是path的操作。 不要让框架限制住你，它仅是最底的基层;在其之上的，应是用创造来筑建的大厦和城楼。

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原始发表：2020年03月06日，如有侵权请联系 cloudcommunity@tencent.com 删除

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【Flutter高级玩法-shape】Path在手，天下我有

【Flutter高级玩法-shape】Path在手，天下我有

一、`shape`属性对应的几类对象

1.从Material组件开始说起

2 `BoxBorder$BorderDirectional 与 BoxBorder$Border`

3 `CircleBorder`

4 `RoundedRectangleBorder`和`ContinuousRectangleBorder`

5 `OutlineInputBorder`和`UnderlineInputBorder`

二、自定义ShapeBorder

1.继承ShapeBorder

2. paint方法

3. `getOuterPath方法`

3.手撕优惠券

三、ClipPath、Card 万物皆可裁剪

1. ClipPath中使用shape

2. Card中使用shape

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

【Flutter高级玩法-shape】Path在手，天下我有

【Flutter高级玩法-shape】Path在手，天下我有

一、shape属性 对应的几类对象

1.从Material组件开始说起

2 BoxBorder$BorderDirectional 与 BoxBorder$Border

3 CircleBorder

4 RoundedRectangleBorder和ContinuousRectangleBorder

5 OutlineInputBorder和UnderlineInputBorder

二、自定义ShapeBorder

1.继承ShapeBorder

2. paint方法

3. getOuterPath方法

3.手撕优惠券

三、ClipPath、Card 万物皆可裁剪

1. ClipPath中使用shape

2. Card中使用shape

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

一、`shape`属性对应的几类对象

2 `BoxBorder$BorderDirectional 与 BoxBorder$Border`

3 `CircleBorder`

4 `RoundedRectangleBorder`和`ContinuousRectangleBorder`

5 `OutlineInputBorder`和`UnderlineInputBorder`

3. `getOuterPath方法`