iOS 简单的贝塞尔(UIBezierPath)曲线使用

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在iOS中绘制矢量图或者路径的时候通常会用到 UIBezierPath ，它在 UIKit 中，是CoreGraphics对path的封装。使用 UIBezierPath ，可以绘制直线、椭圆、多边形和贝塞尔曲线等。

使用UIBezierPath的方法

UIBezierPath 是对 CGPathRef 的封装。创建矢量图形时，拆解成一或多条线段，拼接起来，每条线段的终点都是下一条线段的起点。

具体地：

创建一个 UIBezierPath 对象
用 moveToPoint: 设置初始线段的起点
添加线段，定义一或多个子路径
修改 UIBezierPath 的绘图相关的属性，比如stroke path的属性 lineWidth 和 lineJoinStyle ， filled path的属性 usesEvenOddFillRule

如果是矩形或者椭圆之类的特殊图形，可以不用第2步。

(简单的说需要一个起点然后添加连线(addLineToPoint-直线,addQuadCurveToPoint-椭圆)或者其他的)

绘制各类矢量图形

UIBezierPath 包含了几个特殊形状的类方法，很容易使用。

// 创建矩形+ (UIBezierPath *)bezierPathWithRect:(CGRect)rect// 创建圆角矩形+ (UIBezierPath *)bezierPathWithRoundedRect:(CGRect)rect cornerRadius:(CGFloat)cornerRadius// 创建矩形内切圆+ (UIBezierPath *)bezierPathWithOvalInRect:(CGRect)rect// 创建弧形+ (UIBezierPath *)bezierPathWithArcCenter:(CGPoint)center radius:(CGFloat)radius startAngle:(CGFloat)startAngle endAngle:(CGFloat)endAngle clockwise:(BOOL)clockwise

除了这些闭合的特殊路径，也有一些方法用来添加子路径。

// 添加直线- (void)addLineToPoint:(CGPoint)point// 添加弧形线段- (void)addArcWithCenter:(CGPoint)center radius:(CGFloat)radius startAngle:(CGFloat)startAngle endAngle:(CGFloat)endAngle clockwise:(BOOL)clockwise// 添加二阶贝塞尔曲线- (void)addQuadCurveToPoint:(CGPoint)endPoint controlPoint:(CGPoint)controlPoint// 添加三阶贝塞尔曲线- (void)addCurveToPoint:(CGPoint)endPoint controlPoint1:(CGPoint)controlPoint1 controlPoint2:(CGPoint)controlPoint2

UIBezierPath 封装了 CGPathRef ，它提供了 CGPath 属性使我们可以获取底层的path。

如果我们还希望修改封装的path，有两种方法。一种是完全用CoreGraphics的函数修改，另一种是混用CoreGraphics和 UIBezierPath 的方法。

UIBezierPath主要是画出形状（或画出一个图形的路径path），他可以配合其他的layer使用（CAShapeLayer，CAGradientLayer等）layer可以添加动画所以结合起来更强大

例如：创建一个简单的弧形

-(UIBezierPath *)confighPathY:(CGFloat)y X:(CGFloat)x

{

CGFloat width =self.frame.size.width;

[self.movePathremoveAllPoints];

[self.movePathmoveToPoint:CGPointMake(0,0)];

[self.movePathaddLineToPoint:CGPointMake(width,0)];

[self.movePathaddQuadCurveToPoint:CGPointMake(0,0)controlPoint:CGPointMake(width /2.0 + x<width/2.0?(-x/2.0):(x), y)];

return self.movePath;

}

-(UIBezierPath *)movePath

{

if (_movePath ==nil)

{

_movePath = [UIBezierPathbezierPath];

}

return_movePath;

}

创建好路径之后结合 Layer

// 创建一个shapeLayer

CAShapeLayer *layer = [CAShapeLayerlayer];

layer.frame = showView.bounds; // 与showView的frame一致

layer.strokeColor = [UIColor greenColor].CGColor; // 边缘线的颜色

layer.fillColor = [UIColor clearColor].CGColor; // 闭环填充的颜色

layer.lineCap = kCALineCapSquare; // 边缘线的类型

layer.path = [selfconfighPathY:200 X:100].CGPath; // 从贝塞尔曲线获取到形状

layer.lineWidth = 4.0f; //线条宽度

layer.strokeStart = 0.0f;

layer.strokeEnd = 0.1f;

// 将layer添加进图层

[showView.layer addSublayer:layer];

整合一些简单的动画（路径self.movePath 到 self.originPath的动画）

-(void)animation

{

CABasicAnimation *morph = [CABasicAnimationanimationWithKeyPath:@"path"];

morph.duration = 0.5;

morph.fromValue = (__bridgeid_Nullable)(self.movePath.CGPath);

morph.toValue = (__bridgeid_Nullable)(self.originPath.CGPath);

//移动后位置保持结束后的状态

morph.fillMode=kCAFillModeForwards;

morph.removedOnCompletion =NO;

[self.shapeLayeraddAnimation:morphforKey:nil];

}

（以上的代码不是连贯的只是说明一下场景）

===以上知识大致讲解完毕接来下就是上代码===================

我们自定义一个view，根据手势滑动让曲线跟着移动

GIF效果图：

一下是源代码：

////  CADisplayView.h//  SearchVCDemo////  Created by Programmer two on 16/1/16.//  Copyright © 2016年 linpeng. All rights reserved.//#import <UIKit/UIKit.h>// 16进制转颜色#define UIColorFromRGB(rgbValue)            [UIColor colorWithRed:((float)((rgbValue & 0xFF0000) >> 16))/255.0 green:((float)((rgbValue & 0xFF00) >> 8))/255.0 blue:((float)(rgbValue & 0xFF))/255.0 alpha:1.0]#define kMAINGREEN  UIColorFromRGB(0x3CDC46)@interface CADisplayView : UIView@property (nonatomic,strong) CADisplayLink *displayLink;@property (nonatomic,) CFTimeInterval beginTime;@end

////  CADisplayView.m//  SearchVCDemo////  Created by Programmer two on 16/1/16.//  Copyright © 2016年 linpeng. All rights reserved.//#import "CADisplayView.h"@interface CADisplayView()@property (nonatomic,strong) CAShapeLayer *shapeLayer;@property (nonatomic,strong) UIBezierPath *movePath,*originPath;@end@implementation CADisplayViewCGFloat x;CGFloat y;-(void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{    CGPoint point = [touches.anyObject locationInView:self];    x = point.x;    y = point.y;    [self setNeedsDisplayView];}-(void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{    y = 0;    [self animation];}-(UIBezierPath *)confighPathY:(CGFloat)y X:(CGFloat)x{    CGFloat width = self.frame.size.width;    [self.movePath removeAllPoints];    [self.movePath moveToPoint:CGPointMake(0,0)];    [self.movePath addLineToPoint:CGPointMake(width, 0)];    [self.movePath addQuadCurveToPoint:CGPointMake(0, 0) controlPoint:CGPointMake(width /2.0 + x<width/2.0?(-x/2.0):(x), y)];    return self.movePath;}-(void)animation{    CABasicAnimation *morph = [CABasicAnimation animationWithKeyPath:@"path"];    morph.duration = 0.5;    morph.fromValue = (__bridge id _Nullable)(self.movePath.CGPath);    morph.toValue = (__bridge id _Nullable)(self.originPath.CGPath);   //移动后位置保持结束后的状态    morph.fillMode=kCAFillModeForwards;    morph.removedOnCompletion = NO;        [self.shapeLayer addAnimation:morph forKey:nil];}//刷新path-(void)setNeedsDisplayView{    //除移之前的    [self.shapeLayer removeFromSuperlayer];        self.shapeLayer = [CAShapeLayer layer];    self.shapeLayer.frame = CGRectMake(0, 0, self.frame.size.width, self.frame.size.height);//设置shapeLayer的尺寸和位置    self.shapeLayer.fillColor = [kMAINGREEN colorWithAlphaComponent:0.5].CGColor;//填充颜色为ClearColor    //设置线条的宽度和颜色    self.shapeLayer.lineWidth = 1.0f;    self.shapeLayer.strokeColor = [UIColor clearColor].CGColor;    //让贝塞尔曲线与CAShapeLayer产生联系    self.shapeLayer.path = [self confighPathY:y X:x].CGPath;    //添加并显示    [self.layer addSublayer:self.shapeLayer];}/* 调试发现在drawRect里面处理很耗内存-(void)drawRect:(CGRect)rect{    //除移之前的    [self.shapeLayer removeFromSuperlayer];        self.shapeLayer = [CAShapeLayer layer];    self.shapeLayer.frame = CGRectMake(0, 0, rect.size.width, rect.size.height);//设置shapeLayer的尺寸和位置    self.shapeLayer.fillColor = [kMAINGREEN colorWithAlphaComponent:0.5].CGColor;//填充颜色为ClearColor    //设置线条的宽度和颜色    self.shapeLayer.lineWidth = 1.0f;    self.shapeLayer.strokeColor = [UIColor clearColor].CGColor;    //让贝塞尔曲线与CAShapeLayer产生联系    self.shapeLayer.path = [self confighPathY:y X:x].CGPath;    //添加并显示    [self.layer addSublayer:self.shapeLayer];} */-(UIBezierPath *)movePath{    if (_movePath == nil)    {        _movePath = [UIBezierPath bezierPath];    }    return _movePath;}-(UIBezierPath *)originPath{    if (_originPath == nil)    {        CGFloat width = self.frame.size.width;        _originPath = [UIBezierPath bezierPath];        [_originPath moveToPoint:CGPointMake(0,0)];        [_originPath addLineToPoint:CGPointMake(width, 0)];        [_originPath addQuadCurveToPoint:CGPointMake(0, 0) controlPoint:CGPointMake(width /2.0 + x<width/2.0?(-x/2.0):(x), 0)];    }    return _originPath;}@end

VC调用：

 int w = self.view.frame.size.width;    CADisplayView *v1 = [[CADisplayView alloc] initWithFrame:CGRectMake((self.view.frame.size.width - w)/2.0, 200, w, w)];    [v1 setBackgroundColor:[UIColor whiteColor]];    [self.view addSubview:v1];

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