MJRefresh八MJRefreshAutoFooter

MJRefreshAutoFooter

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AutoFooter的核心是在监听offset的变化时，不判断是否还在拖拽中，只要offset的变化超过了临界值就执行刷新动画，并执行刷新的block或action

- (void)scrollViewContentOffsetDidChange:(NSDictionary *)change
{
    [super scrollViewContentOffsetDidChange:change];
    
    if (self.state != MJRefreshStateIdle || !self.automaticallyRefresh || self.mj_y == 0) return;
    
    if (_scrollView.mj_insetT + _scrollView.mj_contentH > _scrollView.mj_h) { // 内容超过一个屏幕
        // 这里的_scrollView.mj_contentH替换掉self.mj_y更为合理
        if (_scrollView.mj_offsetY >= _scrollView.mj_contentH - _scrollView.mj_h + self.mj_h * self.triggerAutomaticallyRefreshPercent + _scrollView.mj_insetB - self.mj_h) {
            // 防止手松开时连续调用
            CGPoint old = [change[@"old"] CGPointValue];
            CGPoint new = [change[@"new"] CGPointValue];
            if (new.y <= old.y) return;
            
            // 当底部刷新控件完全出现时，才刷新
            [self beginRefreshing];
        }
    }
}

同时也会在gesture的state变化为end的时候做判断

- (void)scrollViewPanStateDidChange:(NSDictionary *)change
{
    [super scrollViewPanStateDidChange:change];
    
    if (self.state != MJRefreshStateIdle) return;
    
    if (_scrollView.panGestureRecognizer.state == UIGestureRecognizerStateEnded) {// 手松开
        if (_scrollView.mj_insetT + _scrollView.mj_contentH <= _scrollView.mj_h) {  // 不够一个屏幕
            if (_scrollView.mj_offsetY >= - _scrollView.mj_insetT) { // 向上拽
                [self beginRefreshing];
            }
        } else { // 超出一个屏幕
            if (_scrollView.mj_offsetY >= _scrollView.mj_contentH + _scrollView.mj_insetB - _scrollView.mj_h) {
                [self beginRefreshing];
            }
        }
    }
}