使用 NSFetchedResultsController 锚定一行

发布于 2024-12-14 08:32:19 字数 2158 浏览 0 评论 0原文

我正在尝试使我的 UITableView 始终在底部有一个特定的行，锚定在那里。

我使用 NSFetchedResultsController 来执行提取，然后使用常规 Apple 样板来检测合并的上下文更改。

我想做的就是在结果底部始终显示一行“不是您要查找的内容？”。我该怎么做？我对自定义单元格类型很满意，但我什至无法将相同类型的单元格锚定到底部。

比 fetchedResultsController 中的内容多添加一行的代码：

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    id <NSFetchedResultsSectionInfo> sectionInfo = [[fetchedResultsController sections] objectAtIndex:section];
    return[sectionInfo numberOfObjects]+1;
}

cellForRowForIndexPath 的代码：

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifierNormal = @"NormalCell";

UITableViewCell *cell = nil;
cell = [tableView CellIdentifierNormal];

    if (cell == nil) {
        cell = [[NormalCell createCell]autorelease];
    }
// For regular results, go configure the cell. For the extra 'Special Row' at bottom, assign it the Special cell.
if([indexPath indexAtPosition:0] <= [[[fetchedResultsController sections] objectAtIndex:0] numberOfObjects])
     [self configureCell:cell atIndexPath:indexPath];
else {
    if (cell == nil) {
        cell = [[SpecialCell createCell] autorelease];
    }
    SpecialCell *nc = (SpecialCell*)cell;
    nc.labelFirstLine.text = @"Not What You're Looking For?";
}
return cell;
}

如果不使用 NSFetchedResultsController，这将起作用，但会发生的情况是，每当更新单元格时，就会从控制器调用“configureCell”方法，该方法对 SpecialCell 一无所知。

来自 - (void)controller:(NSFetchedResultsController *)controller didChangeObject:......

 case NSFetchedResultsChangeUpdate:
        [self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
        break;

这里是configureCell:

- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath {
// Configure the cell
// Go get it from coredata
    NormalCell *vc = (NormalCell*)cell;
NormalObject *no = (NormalCell *)[fetchedResultsController objectAtIndexPath:indexPath];
....<ASSIGNMENT TO CELL HERE>....

}

原文

I'm trying to make it so my UITableView always has a specific row at the bottom, anchored there.

I'm using a NSFetchedResultsController to perform a fetch, and then the regular Apple boilerplate for detecting a merged context change.

What I'd like to do is always have one row at the bottom of the results, "Not What You're Looking For?". How would I do this? I'm comfortable with custom cell types, but I can't get even a cell of the same type to anchor to the bottom.

Code that adds one more row than what is in the fetchedResultsController:

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    id <NSFetchedResultsSectionInfo> sectionInfo = [[fetchedResultsController sections] objectAtIndex:section];
    return[sectionInfo numberOfObjects]+1;
}

Code for cellForRowForIndexPath:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifierNormal = @"NormalCell";

UITableViewCell *cell = nil;
cell = [tableView CellIdentifierNormal];

    if (cell == nil) {
        cell = [[NormalCell createCell]autorelease];
    }
// For regular results, go configure the cell. For the extra 'Special Row' at bottom, assign it the Special cell.
if([indexPath indexAtPosition:0] <= [[[fetchedResultsController sections] objectAtIndex:0] numberOfObjects])
     [self configureCell:cell atIndexPath:indexPath];
else {
    if (cell == nil) {
        cell = [[SpecialCell createCell] autorelease];
    }
    SpecialCell *nc = (SpecialCell*)cell;
    nc.labelFirstLine.text = @"Not What You're Looking For?";
}
return cell;
}

This would work if not using a NSFetchedResultsController, but what happens is that whenever a cell is updated, the method 'configureCell' is being called from the Controller, which knows nothing about SpecialCell.

From - (void)controller:(NSFetchedResultsController *)controller didChangeObject:......

 case NSFetchedResultsChangeUpdate:
        [self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
        break;

And here is configureCell:

- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath {
// Configure the cell
// Go get it from coredata
    NormalCell *vc = (NormalCell*)cell;
NormalObject *no = (NormalCell *)[fetchedResultsController objectAtIndexPath:indexPath];
....<ASSIGNMENT TO CELL HERE>....

}

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