ios学习：UITableview二（下拉刷新）

/*
 实现tableview的下拉刷新
 tableview滑动就会触发这个方法?
 */
-(void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
{
    //当tableview下拉到最后一行的时候才触发
    if (indexPath.row == self.m_data.count - 1) {
        
        //定义一个UIView
        UIView *footSpinnerView = [[UIView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 320.0f, 60.0f)];
        
        //顶一个有刷新图标的view
        UIActivityIndicatorView *activity = [[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(130.0f, 0.0f, 60.0f, 60.0f)];
        activity.color = [UIColor redColor];
        [activity startAnimating];//启动有刷新图标的view
        
        footSpinnerView.backgroundColor = [UIColor grayColor];
        [footSpinnerView addSubview:activity];
        
        //设置footerview
        self.myTableView.tableFooterView = footSpinnerView;
        
     //   self.myTableView.tableHeaderView = footSpinnerView;
        
        dispatch_queue_t queue = dispatch_queue_create("my queue", nil);
        
        //在后台线程添加数据
        dispatch_async(queue, ^(void){
            
            [self.m_data addObject:@"1000"];
            [self.m_data addObject:@"1001"];
            [self.m_data addObject:@"1002"];
            [self.m_data addObject:@"1003"];
            [self.m_data addObject:@"1004"];
            
        });
        
        //添加完数据就重新加载数据
        dispatch_async(queue, ^(void) {
            
            sleep(2);
            dispatch_sync(dispatch_get_main_queue(), ^(void){
                
                [self.myTableView reloadData];
            });
        });
        
       // [self.myTableView reloadData];
        dispatch_release(queue);
        [footSpinnerView release];
        [activity release];
    }
//   else if (indexPath.row == 0) {
//        
//        UIView *footSpinnerView = [[UIView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 320.0f, 60.0f)];
//        UIActivityIndicatorView *activity = [[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(130.0f, 0.0f, 60.0f, 60.0f)];
//        activity.color = [UIColor redColor];
//        [activity startAnimating];
//        
//        footSpinnerView.backgroundColor = [UIColor grayColor];
//        [footSpinnerView addSubview:activity];
//        
//     //   self.myTableView.tableFooterView = footSpinnerView;
//        
//        self.myTableView.tableHeaderView = footSpinnerView;
//        
//        dispatch_queue_t queue = dispatch_queue_create("my queue", nil);
//        
//        dispatch_async(queue, ^(void){
//            
//            [self.m_data insertObject:@"1000" atIndex:0];
////            [self.m_data addObject:@"1001"];
////            [self.m_data addObject:@"1002"];
////            [self.m_data addObject:@"1003"];
////            [self.m_data addObject:@"1004"];
//         //   [self.m_data insertObject:[NSArray arrayWithObject:@"01"] atIndex:0];
//            
//        });
//        
//        dispatch_async(queue, ^(void) {
//            
//            sleep(2);
//            dispatch_sync(dispatch_get_main_queue(), ^(void){
//                
//                [self.myTableView reloadData];
//                [self.myTableView scrollToRowAtIndexPath:[indexPath initWithIndex:3] atScrollPosition:UITableViewScrollPositionNone animated:YES];
//           });
//        });
//        
//
//       dispatch_release(queue);
//        [footSpinnerView release];
//        [activity release];
//    }

    //如果不是最后一行,则把footerview和headerview都设为nil
    else
    {
        self.myTableView.tableFooterView = nil;
        self.myTableView.tableHeaderView = nil;
    }
}