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];
 }
 }