【发布时间】：2017-12-09 06:30:56
【问题描述】：
我试图在加载新数据后让我的 tableview 滚动到底部。例如，我有一个聊天窗口，一旦按下“sendReply”按钮，就会加载新消息，并且我总是希望它在发布数据时滚动到最新消息（在底部）。由于某种原因，self.tableview 重新加载后我的 tableView 不会滚动到底部？
我认为这是因为我的方法中有 rowNumber-1，但是当我尝试将其更改为 -0 时，出现错误：
由于未捕获的异常“NSRangeException”而终止应用程序，原因： '-[UITableView _contentOffsetForScrollingToRowAtIndexPath:atScrollPosition:usingPresentationValues:]: 第 (0) 行的第 (16) 行超出界限 (16)。'
ViewController.m
- (void)scrollTableToBottom {
NSInteger rowNumber = [self. tableView numberOfRowsInSection:0];
if (rowNumber > 0) {
[self. tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:rowNumber-1 inSection:0] atScrollPosition:UITableViewScrollPositionBottom animated:YES];
}
}
- (IBAction)sendReply:(id)sender {
if ([self.messageData count] > 0) {
self.sendButton.hidden = YES;
self.activityIndicator.hidden = NO;
[self.activityIndicator startAnimating];
NSMutableDictionary *nodeData = [NSMutableDictionary new];
[nodeData setObject:@"messages" forKey:@"type"];
NSDictionary *messageValues = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:self.replyField.text, nil] forKeys:[NSArray arrayWithObjects:@"value", nil]];
NSDictionary *finalMessage = [NSDictionary dictionaryWithObject:[NSArray arrayWithObject:messageValues] forKey:@"und"];
[nodeData setObject:finalMessage forKey:@"body"];
NSString *otherUID = [self.messageData objectForKey:@"uid"];
NSString *userValue = otherUID;
NSDictionary *targetMessage = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:userValue, nil] forKeys:[NSArray arrayWithObjects:@"value", nil]];
NSDictionary *finalUser = [NSDictionary dictionaryWithObject:[NSArray arrayWithObject:targetMessage] forKey:@"und"];
[nodeData setObject:finalUser forKey:@"field_targetuser"];
[nodeData setValue: @"Re:" forKey:@"title"];
NSDictionary *userDictInfo = (NSDictionary*) [NSKeyedUnarchiver unarchiveObjectWithData:[[NSUserDefaults standardUserDefaults] objectForKey:@"diosSession"]];
DIOSSession *session = [DIOSSession sharedSession];
[session setUser:userDictInfo];
[session user];
NSString *uid = [session user][@"user"][@"uid"];
[DIOSNode nodeSave:nodeData success:^(AFHTTPRequestOperation *operation, id responseObject) {
self.replyField.text = @"";
[self.tableView reloadData];
[self scrollTableToBottom];
self.sendButton.hidden = NO;
[self.activityIndicator stopAnimating];
self.activityIndicator.hidden = YES;
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(@"Node did not save!");
}];
} else if ([self.messageDataFriends count] > 0) {
self.sendButton.hidden = YES;
self.activityIndicator.hidden = NO;
[self.activityIndicator startAnimating];
NSMutableDictionary *nodeData = [NSMutableDictionary new];
[nodeData setObject:@"messages" forKey:@"type"];
NSDictionary *messageValues = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:self.replyField.text, nil] forKeys:[NSArray arrayWithObjects:@"value", nil]];
NSDictionary *finalMessage = [NSDictionary dictionaryWithObject:[NSArray arrayWithObject:messageValues] forKey:@"und"];
[nodeData setObject:finalMessage forKey:@"body"];
NSString *otherUID = [self.messageDataFriends objectForKey:@"uid2"];
NSString *userValue = otherUID;
NSDictionary *targetMessage = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:userValue, nil] forKeys:[NSArray arrayWithObjects:@"value", nil]];
NSDictionary *finalUser = [NSDictionary dictionaryWithObject:[NSArray arrayWithObject:targetMessage] forKey:@"und"];
[nodeData setObject:finalUser forKey:@"field_targetuser"];
[nodeData setValue: @"Re:" forKey:@"title"];
NSString *uid = [[[DIOSSession sharedSession] user] objectForKey:@"uid"];
[DIOSNode nodeSave:nodeData success:^(AFHTTPRequestOperation *operation, id responseObject) {
dispatch_async(dispatch_get_main_queue(), ^{
self.replyField.text = @"";
[self.tableView reloadData];
[self scrollTableToBottom];
self.sendButton.hidden = NO;
[self.activityIndicator stopAnimating];
self.activityIndicator.hidden = YES;
});
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(@"Node did not save!");
}];
}
}
【问题讨论】：
-
您需要
-1，因为最后一行是“count - 1”。你说表格不会滚动到底部。当您调用scrollTableToBottom方法时，它实际上做了什么？另外，您是否意识到在对DIOSNode nodeSave的 2 次调用中的 1 次中，您没有在主线程上调用reloadData和scrollTableToBottom？ -
@rmaddy 表格滚动到倒数第二个单元格（因此它确实滚动到“底部”，但不是非常底部 - 这是新添加的单元格）。如果我在数据重新加载之前调用 scrollTableToBottom，确实，它会滚动到最底部。
-
在那之后你可以手动滚动实际的最后一行吗？
-
@rmaddy 是的，我可以
标签： ios objective-c uitableview