简单的泡泡View：
@interface UIPaopaoView : UIView

@end

@implementation UIPaopaoView{
CGFloat kArrowHeight; //箭头高度
CGFloat kArrowWidth; //箭头宽度
CGFloat kCornerRadius; //圆角半径
CGFloat kArrowPosition; //参与箭头起点计算的值
CGFloat kCornerRadiusArrowPadding;//箭头与圆角间距
}

• (instancetype)initWithFrame:(CGRect)frame{
  self = [super initWithFrame:frame];
  if(self){
  //箭头高度
  kArrowHeight = 8.0;
  //箭头宽度
  kArrowWidth = 15.0;
  //圆角
  kCornerRadius = 10.0;
  //箭头与圆角间距
  kCornerRadiusArrowPadding = 10.0;
  //箭头位置居左
  kArrowPosition = kCornerRadius + kCornerRadiusArrowPadding;
  //箭头位置居中
  //kArrowPosition = 0.5 * self.frame.size.width - 0.5 * kArrowWidth;
  //箭头位置居右
  //kArrowPosition = self.frame.size.width - kCornerRadius - kArrowWidth - kCornerRadiusArrowPadding;

    //设置阴影颜色
    self.layer.shadowColor = [UIColor colorWithRed:0.0 green:0.0 blue:1.0 alpha:1.0].CGColor;
    //设置阴影不透明度
    self.layer.shadowOpacity = 0.5;
    //设置阴影偏移量
    self.layer.shadowOffset = CGSizeMake(0, 0);
    //设置阴影圆角
    self.layer.shadowRadius = 2.0;
    
    //泡泡
    UIView *paopao = [[UIView alloc] initWithFrame: self.bounds];
    paopao.backgroundColor = [UIColor whiteColor];
    paopao.layer.cornerRadius = 3.0;
    paopao.layer.masksToBounds = YES;
    paopao.layer.mask = [self drawPaoPaoViewMaskLayer:paopao];
    
    [self addSubview:paopao];
  

  }
  return self;
  }

///绘制遮罩层

• (CAShapeLayer *)drawPaoPaoViewMaskLayer:(UIView *)paopaoView
  {
  CAShapeLayer *maskLayer = [CAShapeLayer layer];
  maskLayer.frame = paopaoView.bounds;
  //右上弧中心
  CGPoint topRightArcCenter = CGPointMake(self.frame.size.width - kCornerRadius, kArrowHeight + kCornerRadius);
  //左上弧中心
  CGPoint topLeftArcCenter = CGPointMake(kCornerRadius, kArrowHeight + kCornerRadius);
  //右下弧中心
  CGPoint bottomRightArcCenter = CGPointMake(self.frame.size.width - kCornerRadius, self.
  frame.size.height- kArrowHeight - kCornerRadius);
  //左下弧中心
  CGPoint bottomLeftArcCenter = CGPointMake(kCornerRadius, self.frame.size.height - kArrowHeight - kCornerRadius);

  UIBezierPath *path = [UIBezierPath bezierPath];
  //将接收器的当前点移动到指定位置
  [path moveToPoint: CGPointMake(0, kArrowHeight + kCornerRadius)];
  //向接收器的路径追加一条直线(左侧直线)
  [path addLineToPoint: CGPointMake(0, bottomLeftArcCenter.y)];
  //添加左下角弧线
  [path addArcWithCenter: bottomLeftArcCenter radius: kCornerRadius startAngle: -M_PI endAngle: -M_PI-M_PI_2 clockwise: NO];
  //指向下的箭头
  [path addLineToPoint: CGPointMake(kArrowPosition, self.frame.size.height - kArrowHeight)];
  [path addLineToPoint: CGPointMake(kArrowPosition + 0.5 * kArrowWidth, self.frame.size.height)];
  [path addLineToPoint: CGPointMake(kArrowPosition+kArrowWidth, self.frame.size.height - kArrowHeight)];
  [path addLineToPoint: CGPointMake(self.frame.size.width - kCornerRadius, self.frame.size.height - kArrowHeight)];

  //添加右下角弧线
  [path addArcWithCenter: bottomRightArcCenter radius: kCornerRadius startAngle: -M_PI-M_PI_2 endAngle: -M_PI * 2 clockwise: NO];
  //向接收器的路径追加一条直线(右侧直线)
  [path addLineToPoint: CGPointMake(self.frame.size.width, kArrowHeight+kCornerRadius)];
  //添加右上角弧线
  [path addArcWithCenter: topRightArcCenter radius: kCornerRadius startAngle: 0 endAngle: -M_PI_2 clockwise: NO];
  //指向上的箭头
  //[path addLineToPoint: CGPointMake(kArrowPosition + kArrowWidth, kArrowHeight)];
  //[path addLineToPoint: CGPointMake(kArrowPosition + 0.5 * kArrowWidth, 0)];
  //[path addLineToPoint: CGPointMake(kArrowPosition, kArrowHeight)];
  //[path addLineToPoint: CGPointMake(kCornerRadius, kArrowHeight)];

  //添加左上角弧线
  [path addArcWithCenter: topLeftArcCenter radius: kCornerRadius startAngle: -M_PI_2 endAngle: -M_PI clockwise: NO];
  //关闭路径
  [path closePath];

  maskLayer.path = path.CGPath;

  return maskLayer;
  }

@end