Question

ios 怎样使tableviewhead随着tableview的拉伸变大

Answer 1

你的目的是下拉的时候避免出现UITableView的背景吧，导致颜色、样式的不同意。
如果是这个目的可以这么写一个Cagetory
.h

#import <UIKit/UIKit.h>

@interface UITableView (configure)

- (UIView *)topBackgroundViewWith:(UIColor *)color;

@property (nonatomic, strong) UIView *topBackgroundView;

@end

.m
#import "UITableView+configure.h"

#import <objc/runtime.h>

@implementation UITableView (configure)

- (UIView *)topBackgroundViewWith:(UIColor *)color {

self.backgroundColor = [UIColor clearColor];

if (self.backgroundView == nil) {

self.backgroundView = [[UIView alloc] init];

}

UIView *topBackgroundView = [[UIView alloc] init];

topBackgroundView.backgroundColor = color;

[self.backgroundView addSubview:topBackgroundView];

self.topBackgroundView = topBackgroundView;

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

return topBackgroundView;

}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context {

if ([keyPath isEqualToString:@"contentOffset"]) {

self.topBackgroundView.frame = CGRectMake(0, 0, CGRectGetWidth(self.frame), MAX(self.contentInset.top - self.contentOffset.y, 0));

}

}

static const void *topBackgroundViewKey = &topBackgroundViewKey;

- (void)setTopBackgroundView:(UIView *)topBackgroundView {

objc_setAssociatedObject(self, &topBackgroundViewKey, topBackgroundView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);

}

- (UIView *)topBackgroundView {

return objc_getAssociatedObject(self, &topBackgroundViewKey);

}

- (void)dealloc {

[self removeObserver:self forKeyPath:@"contentOffset"];

}

@end