网上都是这一类代码[tableview setContentOffset:CGPointMake(0,0) animated:NO];

应该是我有加了navigationItem，这个方法会遮住第一个item，后来找到了这个方法

 let section = self.query.numberOfSections()
      if(section > 0 ){
      let row = self.query.numberOfRowsInSection(0)
          if (row > 0){
              let indexPath = NSIndexPath(forRow: 0,inSection: 0)
              self.query.scrollToRowAtIndexPath(indexPath,atScrollPosition: UITableViewScrollPosition.Top,animated: true)
         }
}