帮助NSNotifcation和异步下载 [英] Help With NSNotifcation and Asynchronous Downloading

问题描述

我正在从一个视图向另一个视图发送通知。我的问题是，仅在tableview滚动时，才会在cellForRowAtIndexPath方法中调用的视图中的通知被发送。图像下载后，如何停止此操作并使其发送通知？这是我的代码： https://gist.github.com/756302

I am sending a notification from one view to another view. My problem is that the notification in the view that I am calling in my cellForRowAtIndexPath method is only getting sent when the tableview is scrolling. How can I stop this and make it send the notification once the images have downloaded? Here is my code: https://gist.github.com/756302

谢谢

MKDev

推荐答案

据我了解您的代码，该消息将触发整个表的重新加载。那应该导致细胞的刷新。

as far as I understand your code, the message will trigger the reload of the whole table. That should lead to a refresh of the cells.

因此，您需要在第76行中检查是否正在绘制单元格，因为完成消息触发了重新加载（并且图像现已准备就绪）显示），或者如果您需要启动图像的异步下载。

Thus, you'll need to check in line 76, if the cell is being drawn because a reload was triggered from the finish-message (and the image is now ready to display) or if you need to start the asynchronous download of the image.

我想检查的第一件事是在reloadTableView中设置一个属性：

The first thing which comes into my mind to check this is to set a property in reloadTableView:

- (void)reloadTableView
{
    [[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"aaa"];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:@"name" object:nil];
    NSLog(@"removeobserver");
    loadImageFinished = YES;
    // if your table has several sections you'll need to adopt the section number 
    NSIndexSet *indices = [[NSIndexSet alloc] initWithIndex:0];
    [self.tableView reloadSections:indices withRowAnimation:UITableViewRowAnimationFade];
    [indices release];
}

然后添加

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
   ...
   if (loadImageFinished) {
      ... 
   } else {
      [asyncImage loadImageFromURL:[NSURL URLWithString:pathImage]];
   }
   ...
}

请注意是重新加载表的其他原因-视图可能已经消失或卸载，并且您可能不希望多次触发异步加载。

Note that there could be other reasons why the table is being reloaded - the view could have been disappeared or unloaded and you might not wish to trigger your asynnchronous loading several times.

这篇关于帮助NSNotifcation和异步下载的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！