实现tableview的下拉刷新

-(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UIViewUIView *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]; } }