Android 怎么实现贝塞尔曲线经过点 ios贝塞尔曲线

1、贝塞尔曲线

• 贝塞尔曲线（Bézier curve），又称贝兹曲线或贝济埃曲线，是应用于二维图形应用程序的数学曲线。一般的矢量图形软件通过它来精确画出曲线，贝兹曲线由线段与节点组成，节点是可拖动的支点，线段像可伸缩的皮筋，我们在绘图工具上看到的钢笔工具就是来做这种矢量曲线的。贝塞尔曲线是计算机图形学中相当重要的参数曲线，在一些比较成熟的位图软件中也有贝塞尔曲线工具，如 PhotoShop 等。在 Flash4 中还没有完整的曲线工具，而在 Flash5 里面已经提供出贝塞尔曲线工具。
• 二阶贝塞尔曲线示意图
• 三阶贝塞尔曲线示意图
• 贝塞尔路径（UIBezierPath）是 iOS UIKit 框架中对 Quartz 2D 绘图的封装。实际操作起来，使用贝塞尔路径，更为方便。用法与 CGContextRef 类似，但是 OC 对其进行了封装，更加面向对象。
• 贝塞尔路径常用的方法

// 设置起始点
    - (void)moveToPoint:(CGPoint)point;

    // 添加直线到一点
    - (void)addLineToPoint:(CGPoint)point;

    // 封闭闭路径
    - (void)closePath;

    // 返回一个描述椭圆的路径
    + (UIBezierPath *)bezierPathWithOvalInRect:(CGRect)rect;

    // 贝塞尔曲线
    - (void)addQuadCurveToPoint:(CGPoint)endPoint controlPoint:(CGPoint)controlPoint;

    // 三次贝塞尔曲线
    - (void)addCurveToPoint:(CGPoint)endPoint controlPoint1:(CGPoint)controlPoint1 controlPoint2:(CGPoint)controlPoint2;

    // 绘制圆弧
    - (void)addArcWithCenter:(CGPoint)center radius:(CGFloat)radius startAngle:(CGFloat)startAngle endAngle:(CGFloat)endAngle clockwise:(BOOL)clockwise;
    // 设置起始点
    - (void)moveToPoint:(CGPoint)point;

    // 添加直线到一点
    - (void)addLineToPoint:(CGPoint)point;

    // 封闭闭路径
    - (void)closePath;

    // 返回一个描述椭圆的路径
    + (UIBezierPath *)bezierPathWithOvalInRect:(CGRect)rect;

    // 贝塞尔曲线
    - (void)addQuadCurveToPoint:(CGPoint)endPoint controlPoint:(CGPoint)controlPoint;

    // 三次贝塞尔曲线
    - (void)addCurveToPoint:(CGPoint)endPoint controlPoint1:(CGPoint)controlPoint1 controlPoint2:(CGPoint)controlPoint2;

    // 绘制圆弧
    - (void)addArcWithCenter:(CGPoint)center radius:(CGFloat)radius startAngle:(CGFloat)startAngle endAngle:(CGFloat)endAngle clockwise:(BOOL)clockwise;

2、基本图形的绘制

• 贝塞尔路径基本图形的绘制详情见 Quartz 2D 二维绘图 基本图形绘制

3、二三阶贝塞尔曲线示例

3.1 二阶贝塞尔曲线示例

• QBezierPathView.h

@interface QBezierPathView : UIView

    @end
    @interface QBezierPathView : UIView

    @end

• QBezierPathView.m

@interface QBezierPathView ()

    /// 路径
    @property (nonatomic, strong) UIBezierPath *path;

    /// 起始点
    @property (nonatomic, assign) CGPoint startP;

    /// 终止点
    @property (nonatomic, assign) CGPoint endP;

    /// 控制点
    @property (nonatomic, assign) CGPoint controlP;

    /// 线的颜色
    @property (nonatomic, strong) UIColor *pathColor;

    /// 线的宽度
    @property (nonatomic, assign) CGFloat pathWidth;

    /// 当前触摸的点
    @property (nonatomic, assign) NSUInteger currentTouchP;

    @end

    @implementation QBezierPathView

    /// 初始化
    - (instancetype)initWithFrame:(CGRect)frame {

        if (self = [super initWithFrame:frame]) {

            // 设置初始值

            self.startP    = CGPointMake(20, 300);
            self.endP      = CGPointMake(250, 300);
            self.controlP  = CGPointMake(100, 100);

            self.pathColor = [UIColor redColor];
            self.pathWidth = 2;
        }
        return self;
    }

    /// 绘制二阶贝塞尔曲线
    - (void)drawRect:(CGRect)rect {

        // 绘制贝塞尔曲线

        self.path = [UIBezierPath bezierPath];
        [self.path moveToPoint:self.startP];

        [self.path addQuadCurveToPoint:self.endP controlPoint:self.controlP];

        self.path.lineWidth = self.pathWidth;
        [self.pathColor setStroke];
        [self.path stroke];

        // 绘制辅助线

        self.path = [UIBezierPath bezierPath];

        self.path.lineWidth = 1;
        [[UIColor grayColor] setStroke];

        CGFloat lengths[] = {5};
        [self.path setLineDash:lengths count:1 phase:1];

        [self.path moveToPoint:self.controlP];
        [self.path addLineToPoint:self.startP];
        [self.path stroke];

        [self.path moveToPoint:self.controlP];
        [self.path addLineToPoint:self.endP];
        [self.path stroke];

        // 绘制辅助点及信息

        self.path = [UIBezierPath bezierPathWithArcCenter:self.startP radius:4 startAngle:0 endAngle:M_PI * 2 clockwise:YES];
        [[UIColor blackColor] setStroke];
        [self.path fill];

        self.path = [UIBezierPath bezierPathWithArcCenter:self.endP radius:4 startAngle:0 endAngle:M_PI * 2 clockwise:YES];
        [[UIColor blackColor] setStroke];
        [self.path fill];

        self.path = [UIBezierPath bezierPathWithArcCenter:self.controlP radius:3 startAngle:0 endAngle:M_PI * 2 clockwise:YES];
        self.path.lineWidth = 2;
        [[UIColor blackColor] setStroke];
        [self.path stroke];

        CGRect startMsgRect = CGRectMake(self.startP.x + 8, self.startP.y - 7, 50, 20);
        [@"起始点" drawInRect:startMsgRect withAttributes:nil];

        CGRect endMsgRect = CGRectMake(self.endP.x + 8, self.endP.y - 7, 50, 20);
        [@"终止点" drawInRect:endMsgRect withAttributes:nil];

        CGRect control1MsgRect = CGRectMake(self.controlP.x + 8, self.controlP.y - 7, 50, 20);
        [@"控制点" drawInRect:control1MsgRect withAttributes:nil];
    }

    /// 触摸开始
    - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event {

        // 获取触摸点位置
        CGPoint startPoint = [touches.anyObject locationInView:self];

        CGRect startR   = CGRectMake(self.startP.x   - 4, self.startP.y   - 4, 8, 8);
        CGRect endR     = CGRectMake(self.endP.x     - 4, self.endP.y     - 4, 8, 8);
        CGRect controlR = CGRectMake(self.controlP.x - 4, self.controlP.y - 4, 8, 8);

        // 判断当前触摸点
        if (CGRectContainsPoint(startR, startPoint)) {
            self.currentTouchP = 1;
        } else if (CGRectContainsPoint(endR, startPoint)) {
            self.currentTouchP = 2;
        } else if (CGRectContainsPoint(controlR, startPoint)) {
            self.currentTouchP = 3;
        }
    }

    /// 触摸移动
    - (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event {

        // 获取触摸点位置
        CGPoint touchPoint = [touches.anyObject locationInView:self];

        // 限制触摸点的边界

        if (touchPoint.x < 0) {
            touchPoint.x = 0;
        }

        if (touchPoint.x > self.bounds.size.width) {
            touchPoint.x = self.bounds.size.width;
        }

        if (touchPoint.y < 0) {
            touchPoint.y = 0;
        }

        if (touchPoint.y > self.bounds.size.height) {
            touchPoint.y = self.bounds.size.height;
        }

        // 设置当前触摸点的值
        switch (self.currentTouchP) {
            case 1:
                self.startP = touchPoint;
                break;

            case 2:
                self.endP = touchPoint;
                break;

            case 3:
                self.controlP = touchPoint;
                break;

            default:
                break;
        }

        // 刷新
        [self setNeedsDisplay];
    }

    /// 触摸结束
    - (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event {

        // 释放之前的触摸点
        self.currentTouchP = 0;
    }

    /// 触摸取消
    - (void)touchesCancelled:(NSSet *)touches withEvent:(nullable UIEvent *)event {
        [self touchesEnded:touches withEvent:event];
    }

    @end
    @interface QBezierPathView ()

    /// 路径
    @property (nonatomic, strong) UIBezierPath *path;

    /// 起始点
    @property (nonatomic, assign) CGPoint startP;

    /// 终止点
    @property (nonatomic, assign) CGPoint endP;

    /// 控制点
    @property (nonatomic, assign) CGPoint controlP;

    /// 线的颜色
    @property (nonatomic, strong) UIColor *pathColor;

    /// 线的宽度
    @property (nonatomic, assign) CGFloat pathWidth;

    /// 当前触摸的点
    @property (nonatomic, assign) NSUInteger currentTouchP;

    @end

    @implementation QBezierPathView

    /// 初始化
    - (instancetype)initWithFrame:(CGRect)frame {

        if (self = [super initWithFrame:frame]) {

            // 设置初始值

            self.startP    = CGPointMake(20, 300);
            self.endP      = CGPointMake(250, 300);
            self.controlP  = CGPointMake(100, 100);

            self.pathColor = [UIColor redColor];
            self.pathWidth = 2;
        }
        return self;
    }

    /// 绘制二阶贝塞尔曲线
    - (void)drawRect:(CGRect)rect {

        // 绘制贝塞尔曲线

        self.path = [UIBezierPath bezierPath];
        [self.path moveToPoint:self.startP];

        [self.path addQuadCurveToPoint:self.endP controlPoint:self.controlP];

        self.path.lineWidth = self.pathWidth;
        [self.pathColor setStroke];
        [self.path stroke];

        // 绘制辅助线

        self.path = [UIBezierPath bezierPath];

        self.path.lineWidth = 1;
        [[UIColor grayColor] setStroke];

        CGFloat lengths[] = {5};
        [self.path setLineDash:lengths count:1 phase:1];

        [self.path moveToPoint:self.controlP];
        [self.path addLineToPoint:self.startP];
        [self.path stroke];

        [self.path moveToPoint:self.controlP];
        [self.path addLineToPoint:self.endP];
        [self.path stroke];

        // 绘制辅助点及信息

        self.path = [UIBezierPath bezierPathWithArcCenter:self.startP radius:4 startAngle:0 endAngle:M_PI * 2 clockwise:YES];
        [[UIColor blackColor] setStroke];
        [self.path fill];

        self.path = [UIBezierPath bezierPathWithArcCenter:self.endP radius:4 startAngle:0 endAngle:M_PI * 2 clockwise:YES];
        [[UIColor blackColor] setStroke];
        [self.path fill];

        self.path = [UIBezierPath bezierPathWithArcCenter:self.controlP radius:3 startAngle:0 endAngle:M_PI * 2 clockwise:YES];
        self.path.lineWidth = 2;
        [[UIColor blackColor] setStroke];
        [self.path stroke];

        CGRect startMsgRect = CGRectMake(self.startP.x + 8, self.startP.y - 7, 50, 20);
        [@"起始点" drawInRect:startMsgRect withAttributes:nil];

        CGRect endMsgRect = CGRectMake(self.endP.x + 8, self.endP.y - 7, 50, 20);
        [@"终止点" drawInRect:endMsgRect withAttributes:nil];

        CGRect control1MsgRect = CGRectMake(self.controlP.x + 8, self.controlP.y - 7, 50, 20);
        [@"控制点" drawInRect:control1MsgRect withAttributes:nil];
    }

    /// 触摸开始
    - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event {

        // 获取触摸点位置
        CGPoint startPoint = [touches.anyObject locationInView:self];

        CGRect startR   = CGRectMake(self.startP.x   - 4, self.startP.y   - 4, 8, 8);
        CGRect endR     = CGRectMake(self.endP.x     - 4, self.endP.y     - 4, 8, 8);
        CGRect controlR = CGRectMake(self.controlP.x - 4, self.controlP.y - 4, 8, 8);

        // 判断当前触摸点
        if (CGRectContainsPoint(startR, startPoint)) {
            self.currentTouchP = 1;
        } else if (CGRectContainsPoint(endR, startPoint)) {
            self.currentTouchP = 2;
        } else if (CGRectContainsPoint(controlR, startPoint)) {
            self.currentTouchP = 3;
        }
    }

    /// 触摸移动
    - (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event {

        // 获取触摸点位置
        CGPoint touchPoint = [touches.anyObject locationInView:self];

        // 限制触摸点的边界

        if (touchPoint.x < 0) {
            touchPoint.x = 0;
        }

        if (touchPoint.x > self.bounds.size.width) {
            touchPoint.x = self.bounds.size.width;
        }

        if (touchPoint.y < 0) {
            touchPoint.y = 0;
        }

        if (touchPoint.y > self.bounds.size.height) {
            touchPoint.y = self.bounds.size.height;
        }

        // 设置当前触摸点的值
        switch (self.currentTouchP) {
            case 1:
                self.startP = touchPoint;
                break;

            case 2:
                self.endP = touchPoint;
                break;

            case 3:
                self.controlP = touchPoint;
                break;

            default:
                break;
        }

        // 刷新
        [self setNeedsDisplay];
    }

    /// 触摸结束
    - (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event {

        // 释放之前的触摸点
        self.currentTouchP = 0;
    }

    /// 触摸取消
    - (void)touchesCancelled:(NSSet *)touches withEvent:(nullable UIEvent *)event {
        [self touchesEnded:touches withEvent:event];
    }

    @end

• ViewController.m

CGRect frame = CGRectMake(20, 50, self.view.bounds.size.width - 40, 400);

    QBezierPathView *pathView = [[QBezierPathView alloc] initWithFrame:frame];

    pathView.backgroundColor = [UIColor whiteColor];
    pathView.layer.borderWidth = 1;

    [self.view addSubview:pathView];
    CGRect frame = CGRectMake(20, 50, self.view.bounds.size.width - 40, 400);

    QBezierPathView *pathView = [[QBezierPathView alloc] initWithFrame:frame];

    pathView.backgroundColor = [UIColor whiteColor];
    pathView.layer.borderWidth = 1;

    [self.view addSubview:pathView];

• 效果

3.2 三阶贝塞尔曲线示例

• QBezierPathView.h

@interface QBezierPathView : UIView

    @end
    @interface QBezierPathView : UIView

    @end

• QBezierPathView.m

@interface QBezierPathView : UIView
    @interface QBezierPathView ()

    /// 路径
    @property (nonatomic, strong) UIBezierPath *path;

    /// 起始点
    @property (nonatomic, assign) CGPoint startP;

    /// 终止点
    @property (nonatomic, assign) CGPoint endP;

    /// 控制点
    @property (nonatomic, assign) CGPoint controlP1;
    @property (nonatomic, assign) CGPoint controlP2;

    /// 线的颜色
    @property (nonatomic, strong) UIColor *pathColor;

    /// 线的宽度
    @property (nonatomic, assign) CGFloat pathWidth;

    /// 当前触摸的点
    @property (nonatomic, assign) NSUInteger currentTouchP;

    @end

    @implementation QBezierPathView

    /// 初始化
    - (instancetype)initWithFrame:(CGRect)frame {

        if (self = [super initWithFrame:frame]) {

            // 设置初始值

            self.startP    = CGPointMake(20, 300);
            self.endP      = CGPointMake(250, 300);
            self.controlP1  = CGPointMake(100, 100);
            self.controlP2  = CGPointMake(200, 350);

            self.pathColor = [UIColor redColor];
            self.pathWidth = 2;
        }
        return self;
    }

    /// 绘制二阶贝塞尔曲线
    - (void)drawRect:(CGRect)rect {

        // 绘制贝塞尔曲线

        self.path = [UIBezierPath bezierPath];
        [self.path moveToPoint:self.startP];

        [self.path addCurveToPoint:self.endP controlPoint1:self.controlP1 controlPoint2:self.controlP2];

        self.path.lineWidth = self.pathWidth;
        [self.pathColor setStroke];
        [self.path stroke];

        // 绘制辅助线

        self.path = [UIBezierPath bezierPath];

        self.path.lineWidth = 1;
        [[UIColor grayColor] setStroke];

        CGFloat lengths[] = {5};
        [self.path setLineDash:lengths count:1 phase:1];

        [self.path moveToPoint:self.controlP1];
        [self.path addLineToPoint:self.startP];
        [self.path stroke];

        [self.path moveToPoint:self.controlP1];
        [self.path addLineToPoint:self.controlP2];
        [self.path stroke];

        [self.path moveToPoint:self.controlP2];
        [self.path addLineToPoint:self.endP];
        [self.path stroke];

        // 绘制辅助点及信息

        self.path = [UIBezierPath bezierPathWithArcCenter:self.startP radius:4 startAngle:0 endAngle:M_PI * 2 clockwise:YES];
        [[UIColor blackColor] setStroke];
        [self.path fill];

        self.path = [UIBezierPath bezierPathWithArcCenter:self.endP radius:4 startAngle:0 endAngle:M_PI * 2 clockwise:YES];
        [[UIColor blackColor] setStroke];
        [self.path fill];

        self.path = [UIBezierPath bezierPathWithArcCenter:self.controlP1 radius:3 startAngle:0 endAngle:M_PI * 2 clockwise:YES];
        self.path.lineWidth = 2;
        [[UIColor blackColor] setStroke];
        [self.path stroke];

        self.path = [UIBezierPath bezierPathWithArcCenter:self.controlP2 radius:3 startAngle:0 endAngle:M_PI * 2 clockwise:YES];
        self.path.lineWidth = 2;
        [[UIColor blackColor] setStroke];
        [self.path stroke];

        CGRect startMsgRect = CGRectMake(self.startP.x + 8, self.startP.y - 7, 50, 20);
        [@"起始点" drawInRect:startMsgRect withAttributes:nil];

        CGRect endMsgRect = CGRectMake(self.endP.x + 8, self.endP.y - 7, 50, 20);
        [@"终止点" drawInRect:endMsgRect withAttributes:nil];

        CGRect control1MsgRect = CGRectMake(self.controlP1.x + 8, self.controlP1.y - 7, 50, 20);
        [@"控制点1" drawInRect:control1MsgRect withAttributes:nil];

        CGRect control2MsgRect = CGRectMake(self.controlP2.x + 8, self.controlP2.y - 7, 50, 20);
        [@"控制点2" drawInRect:control2MsgRect withAttributes:nil];
    }

    /// 触摸开始
    - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event {

        // 获取触摸点位置
        CGPoint startPoint = [touches.anyObject locationInView:self];

        CGRect startR    = CGRectMake(self.startP.x   - 4, self.startP.y   - 4, 8, 8);
        CGRect endR      = CGRectMake(self.endP.x     - 4, self.endP.y     - 4, 8, 8);
        CGRect controlR1 = CGRectMake(self.controlP1.x - 4, self.controlP1.y - 4, 8, 8);
        CGRect controlR2 = CGRectMake(self.controlP2.x - 4, self.controlP2.y - 4, 8, 8);

        // 判断当前触摸点
        if (CGRectContainsPoint(startR, startPoint)) {
            self.currentTouchP = 1;
        } else if (CGRectContainsPoint(endR, startPoint)) {
            self.currentTouchP = 2;
        } else if (CGRectContainsPoint(controlR1, startPoint)) {
            self.currentTouchP = 3;
        } else if (CGRectContainsPoint(controlR2, startPoint)) {
            self.currentTouchP = 4;
        }
    }

    /// 触摸移动
    - (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event {

        // 获取触摸点位置
        CGPoint touchPoint = [touches.anyObject locationInView:self];

        // 限制触摸点的边界

        if (touchPoint.x < 0) {
            touchPoint.x = 0;
        }

        if (touchPoint.x > self.bounds.size.width) {
            touchPoint.x = self.bounds.size.width;
        }

        if (touchPoint.y < 0) {
            touchPoint.y = 0;
        }

        if (touchPoint.y > self.bounds.size.height) {
            touchPoint.y = self.bounds.size.height;
        }

        // 设置当前触摸点的值
        switch (self.currentTouchP) {
            case 1:
                self.startP = touchPoint;
                break;

            case 2:
                self.endP = touchPoint;
                break;

            case 3:
                self.controlP1 = touchPoint;
                break;

            case 4:
                self.controlP2 = touchPoint;
                break;

            default:
                break;
        }

        // 刷新
        [self setNeedsDisplay];
    }

    /// 触摸结束
    - (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event {

        // 释放之前的触摸点
        self.currentTouchP = 0;
    }

    /// 触摸取消
    - (void)touchesCancelled:(NSSet *)touches withEvent:(nullable UIEvent *)event {
        [self touchesEnded:touches withEvent:event];
    }

    @end
    @interface QBezierPathView : UIView
    @interface QBezierPathView ()

    /// 路径
    @property (nonatomic, strong) UIBezierPath *path;

    /// 起始点
    @property (nonatomic, assign) CGPoint startP;

    /// 终止点
    @property (nonatomic, assign) CGPoint endP;

    /// 控制点
    @property (nonatomic, assign) CGPoint controlP1;
    @property (nonatomic, assign) CGPoint controlP2;

    /// 线的颜色
    @property (nonatomic, strong) UIColor *pathColor;

    /// 线的宽度
    @property (nonatomic, assign) CGFloat pathWidth;

    /// 当前触摸的点
    @property (nonatomic, assign) NSUInteger currentTouchP;

    @end

    @implementation QBezierPathView

    /// 初始化
    - (instancetype)initWithFrame:(CGRect)frame {

        if (self = [super initWithFrame:frame]) {

            // 设置初始值

            self.startP    = CGPointMake(20, 300);
            self.endP      = CGPointMake(250, 300);
            self.controlP1  = CGPointMake(100, 100);
            self.controlP2  = CGPointMake(200, 350);

            self.pathColor = [UIColor redColor];
            self.pathWidth = 2;
        }
        return self;
    }

    /// 绘制二阶贝塞尔曲线
    - (void)drawRect:(CGRect)rect {

        // 绘制贝塞尔曲线

        self.path = [UIBezierPath bezierPath];
        [self.path moveToPoint:self.startP];

        [self.path addCurveToPoint:self.endP controlPoint1:self.controlP1 controlPoint2:self.controlP2];

        self.path.lineWidth = self.pathWidth;
        [self.pathColor setStroke];
        [self.path stroke];

        // 绘制辅助线

        self.path = [UIBezierPath bezierPath];

        self.path.lineWidth = 1;
        [[UIColor grayColor] setStroke];

        CGFloat lengths[] = {5};
        [self.path setLineDash:lengths count:1 phase:1];

        [self.path moveToPoint:self.controlP1];
        [self.path addLineToPoint:self.startP];
        [self.path stroke];

        [self.path moveToPoint:self.controlP1];
        [self.path addLineToPoint:self.controlP2];
        [self.path stroke];

        [self.path moveToPoint:self.controlP2];
        [self.path addLineToPoint:self.endP];
        [self.path stroke];

        // 绘制辅助点及信息

        self.path = [UIBezierPath bezierPathWithArcCenter:self.startP radius:4 startAngle:0 endAngle:M_PI * 2 clockwise:YES];
        [[UIColor blackColor] setStroke];
        [self.path fill];

        self.path = [UIBezierPath bezierPathWithArcCenter:self.endP radius:4 startAngle:0 endAngle:M_PI * 2 clockwise:YES];
        [[UIColor blackColor] setStroke];
        [self.path fill];

        self.path = [UIBezierPath bezierPathWithArcCenter:self.controlP1 radius:3 startAngle:0 endAngle:M_PI * 2 clockwise:YES];
        self.path.lineWidth = 2;
        [[UIColor blackColor] setStroke];
        [self.path stroke];

        self.path = [UIBezierPath bezierPathWithArcCenter:self.controlP2 radius:3 startAngle:0 endAngle:M_PI * 2 clockwise:YES];
        self.path.lineWidth = 2;
        [[UIColor blackColor] setStroke];
        [self.path stroke];

        CGRect startMsgRect = CGRectMake(self.startP.x + 8, self.startP.y - 7, 50, 20);
        [@"起始点" drawInRect:startMsgRect withAttributes:nil];

        CGRect endMsgRect = CGRectMake(self.endP.x + 8, self.endP.y - 7, 50, 20);
        [@"终止点" drawInRect:endMsgRect withAttributes:nil];

        CGRect control1MsgRect = CGRectMake(self.controlP1.x + 8, self.controlP1.y - 7, 50, 20);
        [@"控制点1" drawInRect:control1MsgRect withAttributes:nil];

        CGRect control2MsgRect = CGRectMake(self.controlP2.x + 8, self.controlP2.y - 7, 50, 20);
        [@"控制点2" drawInRect:control2MsgRect withAttributes:nil];
    }

    /// 触摸开始
    - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event {

        // 获取触摸点位置
        CGPoint startPoint = [touches.anyObject locationInView:self];

        CGRect startR    = CGRectMake(self.startP.x   - 4, self.startP.y   - 4, 8, 8);
        CGRect endR      = CGRectMake(self.endP.x     - 4, self.endP.y     - 4, 8, 8);
        CGRect controlR1 = CGRectMake(self.controlP1.x - 4, self.controlP1.y - 4, 8, 8);
        CGRect controlR2 = CGRectMake(self.controlP2.x - 4, self.controlP2.y - 4, 8, 8);

        // 判断当前触摸点
        if (CGRectContainsPoint(startR, startPoint)) {
            self.currentTouchP = 1;
        } else if (CGRectContainsPoint(endR, startPoint)) {
            self.currentTouchP = 2;
        } else if (CGRectContainsPoint(controlR1, startPoint)) {
            self.currentTouchP = 3;
        } else if (CGRectContainsPoint(controlR2, startPoint)) {
            self.currentTouchP = 4;
        }
    }

    /// 触摸移动
    - (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event {

        // 获取触摸点位置
        CGPoint touchPoint = [touches.anyObject locationInView:self];

        // 限制触摸点的边界

        if (touchPoint.x < 0) {
            touchPoint.x = 0;
        }

        if (touchPoint.x > self.bounds.size.width) {
            touchPoint.x = self.bounds.size.width;
        }

        if (touchPoint.y < 0) {
            touchPoint.y = 0;
        }

        if (touchPoint.y > self.bounds.size.height) {
            touchPoint.y = self.bounds.size.height;
        }

        // 设置当前触摸点的值
        switch (self.currentTouchP) {
            case 1:
                self.startP = touchPoint;
                break;

            case 2:
                self.endP = touchPoint;
                break;

            case 3:
                self.controlP1 = touchPoint;
                break;

            case 4:
                self.controlP2 = touchPoint;
                break;

            default:
                break;
        }

        // 刷新
        [self setNeedsDisplay];
    }

    /// 触摸结束
    - (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event {

        // 释放之前的触摸点
        self.currentTouchP = 0;
    }

    /// 触摸取消
    - (void)touchesCancelled:(NSSet *)touches withEvent:(nullable UIEvent *)event {
        [self touchesEnded:touches withEvent:event];
    }

    @end

• ViewController.m

CGRect frame = CGRectMake(20, 50, self.view.bounds.size.width - 40, 400);

    QBezierPathView *pathView = [[QBezierPathView alloc] initWithFrame:frame];

    pathView.backgroundColor = [UIColor whiteColor];
    pathView.layer.borderWidth = 1;

    [self.view addSubview:pathView];
    CGRect frame = CGRectMake(20, 50, self.view.bounds.size.width - 40, 400);

    QBezierPathView *pathView = [[QBezierPathView alloc] initWithFrame:frame];

    pathView.backgroundColor = [UIColor whiteColor];
    pathView.layer.borderWidth = 1;

    [self.view addSubview:pathView];

• 效果