自定义带弹性效果的pageControl

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分三部分实现，在drawrect方法里画出灰色背景，根据pageCount创建对应个数的dotView放置在对应位置，并隐藏，创建一个CAShapeView类型的layer，根据scrollView的偏移量 构建贝塞尔曲线，画出红色线条，以及形变的大圆。

大圆的形变以及构建思路：

（图引用自：http://kittenyang.com/deformationandgooey/）

下面就是构建A、B、C、D、c1、c2、c3、c4、c5、c6、c7、c8这些点，给A、B、C、D、四个点，一个关于contentOffset的形变量，以达到园形变的效果。value ＝ （半径 ＊ 比例）＊形变因素，其中形变因素于contentOffset相关（在滑动一个页面时会形成这样的关系：0～0.5～0）；CGFloat factor = MIN(0.5, MAX(0, (ABS(scrollView.contentOffset.x - last) / scrollView.frame.size.width)));，构建好点后，根据偏移量，更新点的坐标，生成新的贝塞尔曲线，便生成形变的 圆了。

下面是部分代码：

/** 根据scrollView 更新贝塞尔曲线 */- (void)updateDotLayerScrollView:(UIScrollView *)scrollView{  // 判断滑动方向  BOOL left = (scrollView.contentOffset.x - self.lastOffsetX) >= 0?YES:NO;    // 向左滑动就显示dotView  if (left) {    [self setDotViewShowWithScrollView:scrollView];  }    CGPoint dotCenter = [self calculateDotCenterWithScrollView:scrollView];    // 计算当前偏移量的 归属地（超过一半 就归属后者，反之前者）  int count = (int)(scrollView.contentOffset.x / scrollView.frame.size.width+0.5);    // 根据count 计算归属地 的偏移量  CGFloat last = scrollView.frame.size.width * count;    CGFloat factor = MIN(0.5, MAX(0, (ABS(scrollView.contentOffset.x - last) / scrollView.frame.size.width)));    // extra 是 A、B、C、D四点的 位移量，跟factor有关。而factor跟contentOffset相关，其关系为0～0.5～0；  CGFloat extra = self.SeletedDotRadiu * 4 / 5 * factor;    // 构成贝塞尔曲线的相关点 的计算  A = CGPointMake(dotCenter.x, dotCenter.y - self.SeletedDotRadiu+extra);  B = CGPointMake(left?(dotCenter.x+self.SeletedDotRadiu):(dotCenter.x+self.SeletedDotRadiu+extra * 2), dotCenter.y);  C = CGPointMake(dotCenter.x, dotCenter.y+self.SeletedDotRadiu-extra);  D = CGPointMake(left?(dotCenter.x-self.SeletedDotRadiu-extra*2):(dotCenter.x-self.SeletedDotRadiu), dotCenter.y);  // 1.8 的得来应该是能计算出来的，不过不知道咋算，试出来  CGFloat offset = self.SeletedDotRadiu / 1.8;    c1 = CGPointMake(A.x + offset, A.y);  c2 = CGPointMake(B.x, B.y - offset);  c3 = CGPointMake(B.x, B.y + offset);  c4 = CGPointMake(C.x + offset, C.y);  c5 = CGPointMake(C.x - offset, C.y);  c6 = CGPointMake(D.x, D.y + offset);  c7 = CGPointMake(D.x, D.y - offset);  c8 = CGPointMake(A.x - offset, A.y);    UIBezierPath* ovalPath = [UIBezierPath bezierPath];  CGPoint startPoint = CGPointMake(self.SeletedDotRadiu, CGRectGetHeight(self.frame) / 2.0);  [ovalPath moveToPoint: startPoint];  [ovalPath addLineToPoint:D];  [ovalPath addCurveToPoint:C controlPoint1:c6 controlPoint2:c5];  [ovalPath addCurveToPoint:B controlPoint1:c4 controlPoint2:c3];  [ovalPath addCurveToPoint:A controlPoint1:c2 controlPoint2:c1];  [ovalPath addCurveToPoint:D controlPoint1:c8 controlPoint2:c7];    [ovalPath closePath];  self.dotLayer.path = ovalPath.CGPath;    self.lastOffsetX = scrollView.contentOffset.x;}

    drawRect 方法：

/** 画初始 的背景 */- (void)drawRect:(CGRect)rect {    // 控件垂直方向中心  CGFloat verticalCenter = rect.size.height / 2.0;  // 圆点 半径  CGFloat dotR = self.dotRadiu;    // 选中圆点 半径  CGFloat selectedDotR = self.SeletedDotRadiu;  // 圆心距离  CGFloat distanceCenter = (rect.size.width - 2 * selectedDotR) / (self.pageCount - 1);    UIBezierPath *path = [UIBezierPath bezierPathWithRect:CGRectMake(selectedDotR, (rect.size.height - self.lineWidth) / 2.0, rect.size.width - 2 * selectedDotR, self.lineWidth)];    [self.color setFill];  for (int i = 0; i < self.pageCount; i++) {        UIBezierPath *dotPath = [UIBezierPath bezierPathWithArcCenter:CGPointMake(selectedDotR + distanceCenter * i, verticalCenter) radius:dotR startAngle:0 endAngle:M_PI * 2 clockwise:YES];    [path appendPath:dotPath];  }  [path fill];  }

完整代码：http://pan.baidu.com/s/1i4y78gt

原标题：自定义带弹性效果的pageControl

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