清华大佬耗费三个月吐血整理的几百G的资源，免费分享！....>>>

//改变MJ文件中的MJRefreshBackFooter.h  文件
//改变此文件中的几行代码即可实现
//共改两处
// 下面的是MJRefreshBackFooter.m文件

#import "MJRefreshBackFooter.h"

@interface MJRefreshBackFooter()
@property (assign, nonatomic) NSInteger lastRefreshCount;
@property (assign, nonatomic) CGFloat lastBottomDelta;
@end

@implementation MJRefreshBackFooter

#pragma mark - 实现父类的方法
- (void)scrollViewContentOffsetDidChange:(NSDictionary *)change
{
    [super scrollViewContentOffsetDidChange:change];
    
    // 如果正在刷新，直接返回
    if (self.state == MJRefreshStateRefreshing || self.state == MJRefreshStateNoMoreData) return;
    
    _scrollViewOriginalInset = self.scrollView.contentInset;
    
    // 当前的contentOffset
    CGFloat currentOffsetY = self.scrollView.mj_offsetY;
    // 尾部控件刚好出现的offsetY
    CGFloat happenOffsetY = [self happenOffsetY];
    // 如果是向下滚动到看不见尾部控件，直接返回
    if (currentOffsetY <= happenOffsetY) return;
    
    CGFloat pullingPercent = (currentOffsetY - happenOffsetY) / self.mj_h;
    if (self.scrollView.isDragging) {
        self.pullingPercent = pullingPercent;
#pragma mark- 下面注释掉得是MJ原来的代码
        // 普通 和 即将刷新 的临界点
//        CGFloat normal2pullingOffsetY = happenOffsetY + self.mj_h;
        [self beginRefreshing];
//        if (self.state == MJRefreshStateIdle && currentOffsetY > normal2pullingOffsetY) {
//            // 转为即将刷新状态
//            self.state = MJRefreshStatePulling;
//        } else if (self.state == MJRefreshStatePulling && currentOffsetY <= normal2pullingOffsetY) {
//            // 转为普通状态
//            self.state = MJRefreshStateIdle;
//        }
    } else if (self.state == MJRefreshStatePulling) {// 即将刷新 && 手松开
        // 开始刷新
        [self beginRefreshing];
    } else if (pullingPercent < 1) {
        self.pullingPercent = pullingPercent;
    }
}

- (void)scrollViewContentSizeDidChange:(NSDictionary *)change
{
    [super scrollViewContentSizeDidChange:change];
    
    // 内容的高度
    CGFloat contentHeight = self.scrollView.mj_contentH;
    // 表格的高度
    CGFloat scrollHeight = self.scrollView.mj_h - self.scrollViewOriginalInset.top - self.scrollViewOriginalInset.bottom;
    // 这里一定是用：self.scrollView.mj_insetT 和 self.scrollViewOriginalInset.bottom;
    // 设置位置和尺寸
    self.mj_y = MAX(contentHeight, scrollHeight);
}

- (void)setState:(MJRefreshState)state
{
    MJRefreshCheckState
    
    // 根据状态来设置属性
    if (state == MJRefreshStateNoMoreData || state == MJRefreshStateIdle) {
        // 刷新完毕
        if (MJRefreshStateRefreshing == oldState) {
            [UIView animateWithDuration:MJRefreshSlowAnimationDuration animations:^{
                self.scrollView.mj_insetB -= self.lastBottomDelta;
                
                // 自动调整透明度
                if (self.isAutoChangeAlpha) self.alpha = 0.0;
            } completion:^(BOOL finished) {
                self.pullingPercent = 0.0;
            }];
        }
        
        CGFloat deltaH = [self heightForContentBreakView];
        NSInteger currentCount = [self totalDataCountInScrollView];
        // 刚刷新完毕
        if (MJRefreshStateRefreshing == oldState && deltaH > 0 && currentCount != self.lastRefreshCount) {
            self.scrollView.mj_offsetY = self.scrollView.mj_offsetY;
        }
    } else if (state == MJRefreshStateRefreshing) {
        // 记录刷新前的数量
        self.lastRefreshCount = [self totalDataCountInScrollView];
        
        [UIView animateWithDuration:MJRefreshFastAnimationDuration animations:^{
            CGFloat bottom = self.mj_h + self.scrollViewOriginalInset.bottom;
            CGFloat deltaH = [self heightForContentBreakView];
            if (deltaH < 0) { // 如果内容高度小于view的高度
                bottom -= deltaH;
            }
            self.lastBottomDelta = bottom - self.scrollView.mj_insetB;
            self.scrollView.mj_insetB = bottom;
#warning 上拉刷新
            #pragma mark- 下面注释掉得是MJ原来的代码   原本加的是self.mj_h  改为0
            self.scrollView.mj_offsetY = [self happenOffsetY] +0;// self.mj_h;
        } completion:^(BOOL finished) {
            [self executeRefreshingCallback];
        }];
    }
}

#pragma mark - 公共方法
- (void)endRefreshing
{
    if ([self.scrollView isKindOfClass:[UICollectionView class]]) {
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            [super endRefreshing];
        });
    } else {
        [super endRefreshing];
    }
}

#pragma mark - 私有方法
#pragma mark 获得scrollView的内容 超出 view 的高度
- (CGFloat)heightForContentBreakView
{
    CGFloat h = self.scrollView.frame.size.height - self.scrollViewOriginalInset.bottom - self.scrollViewOriginalInset.top;
    return self.scrollView.contentSize.height - h;
}

#pragma mark 刚好看到上拉刷新控件时的contentOffset.y
- (CGFloat)happenOffsetY
{
    CGFloat deltaH = [self heightForContentBreakView];
    if (deltaH > 0) {
        return deltaH - self.scrollViewOriginalInset.top;
    } else {
        return - self.scrollViewOriginalInset.top;
    }
}

- (NSInteger)totalDataCountInScrollView
{
    NSInteger totalCount = 0;
    if ([self.scrollView isKindOfClass:[UITableView class]]) {
        UITableView *tableView = (UITableView *)self.scrollView;
        
        for (NSInteger section = 0; section<tableView.numberOfSections; section++) {
            totalCount += [tableView numberOfRowsInSection:section];
        }
    } else if ([self.scrollView isKindOfClass:[UICollectionView class]]) {
        UICollectionView *collectionView = (UICollectionView *)self.scrollView;
        
        for (NSInteger section = 0; section<collectionView.numberOfSections; section++) {
            totalCount += [collectionView numberOfItemsInSection:section];
        }
    }
    return totalCount;
}
@end