解決：
1.初始化一個(gè)可變字典
2.在willDisplayHeaderView存儲(chǔ)高度
3.在estimatedHeightForHeaderInSection判斷是否已有高度
4.heightForHeaderInSection判斷是否存儲(chǔ)

//頭部高度存儲(chǔ)
- (void)tableView:(UITableView *)tableView willDisplayHeaderView:(UIView *)view forSection:(NSInteger)section{
//    NSLog(@"HeaderView%f",view.size.height);
    DynamicListItem * item = self.dynamicArr[section];
    CGFloat height = [[self.headerHeightDic objectForKey:item.dynamicId] doubleValue];
    if (height <= 0) {
        [self.headerHeightDic setObject:@(view.size.height) forKey:item.dynamicId];
    }

}
-(CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section{
    DynamicListItem * item = self.dynamicArr[section];
    CGFloat height = [[self.headerHeightDic objectForKey:item.dynamicId] doubleValue];
    if (height > 0) {
        return height;
    }
    return UITableViewAutomaticDimension;
}

-(CGFloat)tableView:(UITableView *)tableView estimatedHeightForHeaderInSection:(NSInteger)section{
    DynamicListItem * item = self.dynamicArr[section];
    CGFloat height = [[self.headerHeightDic objectForKey:item.dynamicId] doubleValue];
    if (height > 0) {
        return height;
    }
    return 360;
}