UITableView scrollToRowAtIndexPath

Question

我正在尝试让我的表格视图记住它的最后位置,以便在应用程序再次运行后,它将滚动到该位置.要做到这一点,在我的viewWillDisappear:方法中,我得到第一个可见的行号并保存到NSUserDefaults.然后在我的viewDidAppear中我尝试通过发送scrollToRowAtIndexPath到表视图滚动到该行.但是我得到了NSRangeException:

*** Terminating app due to uncaught exception 'NSRangeException', reason: '-[UITableView scrollToRowAtIndexPath:atScrollPosition:animated:]: section (0) beyond bounds (0).

任何帮助赞赏.这是代码:

- (void)viewDidAppear:(BOOL)animated
{
    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];

    if ([userDefaults valueForKey:@"content_row"] != nil)
    {
        int rowToHighlight = [[userDefaults valueForKey:@"content_row"] intValue];
        NSIndexPath * ndxPath= [NSIndexPath indexPathForRow:rowToHighlight inSection:0];
        [contentTableView scrollToRowAtIndexPath:ndxPath atScrollPosition:UITableViewScrollPositionTop  animated:YES];
    }
}

-(void) viewWillDisappear:(BOOL)animated
{
    NSIndexPath *selectedRowPath = [[contentTableView indexPathsForVisibleRows] objectAtIndex:0];
    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    [userDefaults setInteger:selectedRowPath.row forKey:@"content_row"];
}

Answer 1

在调用scrollToRowAtIndexPath之前重新加载TableView数据.

[contentTableView reloadData];

Answer 2

contentTableView可能尚未完成加载数据.