iOS:滚动速度过快时，UITableView会混合数据 [英] iOS: UITableView mixes up data when scrolling too fast

问题描述

我对UITableViewCell进行了子类化，以为其添加自定义外观.在MYTableViewCell的初始级别，我添加了4个子视图:UIImageView和三个UILabel.所有4个子视图均分配有不同的标签.

I've subclassed the UITableViewCell to add custom appearance to it. At the init level of the MYTableViewCell I added 4 subviews: UIImageView, and three UILabel(s). All 4 subviews have a different Tag assigned to them.

在cellForRowAtIndexPath方法内部，我要么创建一个新的单元格(如果一开始不可用)，要么重用可用的单元格，并将适当的文本分配给ui标签.

Inside the cellForRowAtIndexPath method I either create a new cell if it wasn't available at first, or reuse available one and assign the proper text to the ui labels.

我遇到的问题是，如果尝试超快速滚动，则数据会混乱，但是如果我缓慢滚动，则一切正常.

The problem I am having is that if I try to scroll super fast, then the data gets messed up, however if I scroll up and down more slowly, then everything works fine.

有什么想法吗?

下面是代码:

- (MyTableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = @"itemListTableViewCell";
MyTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

DisplayableEntity *displayableEntity = [self.fetchedResultsController objectAtIndexPath:indexPath];

if( ! cell ) {
    cell = [[MyTableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];

    [self tableView:tableView appearanceForCell:cell withEntity:displayableEntity];
} else {

    UIImageView *imageView = (UIImageView *) [cell viewWithTag:IMAGEVIEW_TAG];
    imageView.image = [UIImage imageNamed:displayableEntity.displayImageName];

    UILabel *titleLabel = (UILabel *) [cell viewWithTag:TITLEVIEW_TAG];
    titleLabel.text = displayableEntity.entityName;

    UILabel *itemDescription = (UILabel *) [cell viewWithTag:DESCRIPTION_TAG];
    itemDescription.text = displayableEntity.entityDesctiption;
  }
}

// some code removed to make it brief
- (void)tableView:(UITableView *)tableView appearanceForCell:(MyTableViewCell *)cell withEntity:(DisplayableEntity *)entity {

    // cell image view
    UIImageView *cellImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:[entity displayImageName]]];
    [cellImageView setTag:IMAGEVIEW_TAG];
    [cell addSubview:cellImageView];

    // adding entity name label    
    UILabel *itemTitleName = [self itemTitleNameLabelWithFrame:itemNameLabelRect itemName:[entity entityName]];
    [itemTitleName setTag:TITLEVIEW_TAG];
    [cell addSubview:itemTitleName];

    // adding 'assigned to' label right under the item name label
    UILabel *itemDescriptionLabel = [self itemDescriptionLabelWithFrame:descriptionLabelFrame itemDescription:[entity entityDesctiption]];
    [itemDescriptionLabel setTag:DESCRIPTION_TAG];
    [cell addSubview:itemDescriptionLabel];
}

推荐答案

我在 tableView:cellForRowAtIndexPath:逻辑中看到了一些麻烦应该是:

I see some troubles in tableView:cellForRowAtIndexPath: logic It should be:

1. 出队单元格
2. 如果无法将单元出队，请创建一个新单元
3. 设置所有单元格属性

我的意思是这样的:

- (MyTableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
{
    static NSString *CellIdentifier = @"itemListTableViewCell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
    } // <-- Note there is no else, we should reset properties in both cases

    NSManagedObject *managedObject = [_fetchedResultsController objectAtIndexPath:indexPath];

    cell.textLabel.text = [managedObject valueForKey:@"text"];
    cell.imageView.image = [managedObject valueForKey:@"image"];

    return cell;
}

这篇关于iOS:滚动速度过快时，UITableView会混合数据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！