UITableView 头部效果/放大/移动跟随效果

[self.tableView addObserver:self forKeyPath:@"contentOffset" options:NSKeyValueObservingOptionOld|NSKeyValueObservingOptionNew context:nil];

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context{
    CGPoint oldPoint = [change[@"old"] CGPointValue];
    CGPoint newPoint = [change[@"new"] CGPointValue];
//    NSLog(@"%@",change);
    CGFloat newY = newPoint.y;
    CGFloat oldY = oldPoint.y;
   if ( newY - oldY > 0) { //判断

        self.imageView.y -= newY;

        self.tableView.y = self.imageView.bottom;

        [self.tableView setContentOffset:CGPointMake(, )];

    }
    else if (  newY - oldY < ) {
//        self.imageView.y = self.imageView.y - newY;
//        if (self.imageView.y >= 0) {
//            self.imageView.y = 0;
//        }
//        self.tableView.y = self.imageView.bottom;
        self.imageView.y -= newY;

        self.tableView.y = self.imageView.bottom;

        [self.tableView setContentOffset:CGPointMake(, )];

    }

}

https://github.com/yongliangP/YLSpringHeader

https://github.com/Cloudox/ScrollShowHeaderDemo

https://www.jianshu.com/p/8e4ed860d460

section 圆角 阴影

https://www.cnblogs.com/yeng/p/10540167.html

//===============Cell==================

@interface SubCell : UITableViewCell

@property (nonatomic, strong) SubCellShadowView *bgView;

@property (nonatomic, strong) NSIndexPath *indexPath;

@property (nonatomic) NSInteger rowInSection;//每一组的行数

@end

@implementation SubCell

- (void)awakeFromNib {

    [super awakeFromNib];

    self.selectionStyle = UITableViewCellSelectionStyleNone;

    self.clipsToBounds = NO;

    SubCellShadowView *bgView = [[SubCellShadowView alloc] init];

    [self insertSubview:bgView atIndex:];

    self.bgView= bgView;

    CAShapeLayer *shadow = [CAShapeLayer layer];

    shadow.shadowColor = [UIColor blackColor].CGColor;

    shadow.shadowOffset=CGSizeMake(,);

    shadow.shadowOpacity=0.15;

    [bgView.layeraddSublayer:shadow];

    bgView.shadowLayer= shadow;

    CALayer*line = [CALayerlayer];

    line.backgroundColor = [UIColor groupTableViewBackgroundColor].CGColor;

    [bgView.layeraddSublayer:line];

    bgView.separatorLine= line;

}

-(void)layoutSubviews{

    [super layoutSubviews];

    UIBezierPath*bgBezierPath =nil;

    CGFloat cornerRaduis =7.0;//觉得阴影大的可以把半径调小,半径大的话阴影面积会变大

    if(self.indexPath.row== && self.rowInSection==) {//单组单行

        self.bgView.clipsToBounds=NO;

        self.bgView.frame=self.bounds;

        CGRect rect = UIEdgeInsetsInsetRect(self.bgView.bounds, UIEdgeInsetsMake(, , , ));

        bgBezierPath = [UIBezierPath bezierPathWithRoundedRect:rect byRoundingCorners:UIRectCornerAllCorners cornerRadii:CGSizeMake(cornerRaduis, cornerRaduis)];

    }elseif(self.indexPath.row==) {// 第一行

        self.bgView.clipsToBounds=YES;

        self.bgView.frame = UIEdgeInsetsInsetRect(self.bounds, UIEdgeInsetsMake(-, , , ));

        CGRect rect = UIEdgeInsetsInsetRect(self.bgView.bounds, UIEdgeInsetsMake(, , , ));

        bgBezierPath = [UIBezierPath bezierPathWithRoundedRect:rect byRoundingCorners:(UIRectCornerTopLeft|UIRectCornerTopRight) cornerRadii:CGSizeMake(cornerRaduis, cornerRaduis)];

    }elseif(self.indexPath.row==self.rowInSection-) {// 最后一行

        self.bgView.clipsToBounds=YES;

        self.bgView.frame = UIEdgeInsetsInsetRect(self.bounds, UIEdgeInsetsMake(, , -, ));

        CGRect rect = UIEdgeInsetsInsetRect(self.bgView.bounds, UIEdgeInsetsMake(, , , ));

        bgBezierPath = [UIBezierPath bezierPathWithRoundedRect:rect byRoundingCorners:(UIRectCornerBottomLeft|UIRectCornerBottomRight)  cornerRadii:CGSizeMake(cornerRaduis, cornerRaduis)];

    }else{// 中间行

        self.bgView.clipsToBounds=YES;

        self.bgView.frame = UIEdgeInsetsInsetRect(self.bounds, UIEdgeInsetsMake(, , , ));

        CGRect rect = UIEdgeInsetsInsetRect(self.bgView.bounds, UIEdgeInsetsMake(, , , ));

        bgBezierPath = [UIBezierPathbezierPathWithRect:rect];

    }

    self.bgView.shadowLayer.path= bgBezierPath.CGPath;

    self.bgView.shadowLayer.shadowPath= bgBezierPath.CGPath;

    self.bgView.shadowLayer.fillColor = [UIColor whiteColor].CGColor;

    //分割线 非单组单行 非最后一行

    if(!(self.indexPath.row==&&self.rowInSection==) && !(self.indexPath.row==self.rowInSection-)) {

        self.bgView.separatorLine.frame = CGRectMake(self.bgView.frame.origin.x+, self.bgView.frame.size.height-, self.bgView.frame.size.width-*, 1.0);

    }

}

@end