title: uirefreshcontrol not showing when tableview has many rows
body: <p>my demo code is very simple:i want to load from network when the view controller is present , so i have to call beginRefreshing manually from viewdidload to show the loading refreshControl at beginning</p>
  
  <pre><code>#import "ViewController.h"
  
  @interface ViewController ()&lt;UITableViewDataSource,UITableViewDelegate&gt;
  @property (strong, nonatomic) IBOutlet UITableView *tableView;
  @property(nonatomic,strong) UIRefreshControl* control;
  @end
  
  @implementation ViewController
  
  - (void)viewDidLoad {
      [super viewDidLoad];
      // Do any additional setup after loading the view, typically from a nib.
      self.tableView.tableFooterView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 1, 1)];
  
      self.control = [UIRefreshControl new];
      [self.tableView addSubview:self.control];
      [self.tableView reloadData];
      [self.control beginRefreshing];
  }
  
  - (void)didReceiveMemoryWarning {
      [super didReceiveMemoryWarning];
      // Dispose of any resources that can be recreated.
  }
  
  
  - (void)viewDidAppear:(BOOL)animated
  {
      [super viewDidAppear:animated];
  
  
  }
  
  - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
  {
      return 1;
  }
  
  - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
  {
      return 3;
  }
  
  - (UITableViewCell*)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
  {
      UITableViewCell* cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:nil];
      cell.backgroundColor = [UIColor redColor];
      return cell;
  }
  @end
  </code></pre>
  
  <p>and If i just set number of sections to 1(total rows is 3), every things goes well 
  <a href="https://i.stack.imgur.com/WuJkg.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/WuJkg.png" alt="enter image description here"></a></p>
  
  <p>but if i change number of sections to a bigger number like 10(total rows is 30) , the refresh control will not show</p>
  
  <p><a href="https://i.stack.imgur.com/Pn81g.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Pn81g.png" alt="enter image description here"></a></p>
  
  <p>is it a system bug ? or the way i use refresh control is wrong ?</p>