iOS tableview customcell - 屏幕外单元格上的控件有时不可见

Question

我在包含 5 个单元格的 TableView 中遇到了一个奇怪的错误。由于单元格高度较大，第五个单元格最初不在屏幕上，用户需要向下滚动才能看到它。这些单元格显示一个下载按钮、一个进度指示器，如果下载完成，则显示一个查看按钮而不是下载和进度。

前 4 个单元格显示正确。然而，第五个单元格有时会丢失下载按钮，但有时它会在每次重新启动应用程序时以大约 %50 的几率正确显示。源数据在任何时候都不会更改。

我已经使用断点来查看向下滚动时会发生什么，但我无法发现任何异常，并且在出现单元格时正确提供了数据。

谁能告诉我应该关注哪里？

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {    
    static NSString *MyIdentifier = @"cell1";
    NSDictionary *categoryDictionary= [[appdelegate categoriesArray] objectAtIndex:indexPath.row];    
    categoryTableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier];    
    rect=cell.labelProgressView.frame;
    cell.backgroundColor = [UIColor PGColorBackground];    
    cell.buttonView.hidden=YES;        
    //Set background colors and icons
    switch ([[categoryDictionary valueForKey:@"categoryID"] intValue])
    {
        case 1:
            [cell.buttonView setBackgroundColor: [UIColor PGColorAttractions]] ;
            [cell.labelProgressView setBackgroundColor: [UIColor PGColorAttractions]] ;
            [cell.ivCategoryBannerImage setImage: [UIImage imageNamed:@"attraction-bg"]];
            cell.ivcategoryLogoImage.image =[UIImage imageNamed:@"attractionWhite"];
            break;
        case 2:
            [cell.buttonView setBackgroundColor: [UIColor PGColorRestaurants]];
            [cell.labelProgressView setBackgroundColor: [UIColor PGColorRestaurants]];
            [cell.ivCategoryBannerImage setImage: [UIImage imageNamed:@"restaurant-bg"]];
            cell.ivcategoryLogoImage.image =[UIImage imageNamed:@"restaurantWhite"];
            break;
        case 3:
            [cell.buttonView setBackgroundColor: [UIColor  PGColorShopping]];
            [cell.labelProgressView setBackgroundColor:[UIColor PGColorShopping]];
            [cell.ivCategoryBannerImage setImage: [UIImage imageNamed:@"shopping-bg"]];
            cell.ivcategoryLogoImage.image =[UIImage imageNamed:@"shoppingWhite"];
            break;
        case 4:
            [cell.buttonView setBackgroundColor: [UIColor  PGColorAccomodations]];
            [cell.labelProgressView setBackgroundColor:[UIColor PGColorAccomodations]];
            [cell.ivCategoryBannerImage setImage: [UIImage imageNamed:@"accomodation-bg"]];
            cell.ivcategoryLogoImage.image =[UIImage imageNamed:@"accomodationWhite"];
            break;

        case 5:
            [cell.buttonView setBackgroundColor: [UIColor PGColorArtGalleries]];
            [cell.labelProgressView setBackgroundColor:[UIColor PGColorArtGalleries]];
            [cell.ivCategoryBannerImage setImage: [UIImage imageNamed:@"artGallery-bg"]];
            cell.ivcategoryLogoImage.image =[UIImage imageNamed:@"artGalleryWhite"];
            break;

        default:
            break;            
    }

    //DOWNLOAD Button
    [cell.buttonViewDownload setBackgroundColor:[UIColor clearColor]];
    cell.buttonViewDownload.layer.borderColor=[UIColor whiteColor].CGColor;
    cell.buttonViewDownload.layer.borderWidth=1.0f;
    [cell.buttonViewDownload.titleLabel setFont:[UIFont fontWithName:@"OpenSans-Bold" size:10]];
    [cell.buttonViewDownload setTag:[[categoryDictionary valueForKey:@"categoryID"] intValue]];

    //VIEW Button
    cell.buttonView.layer.borderColor=[UIColor whiteColor].CGColor;
    cell.buttonView.layer.borderWidth=1.0f;
    [cell.buttonView.titleLabel setFont:[UIFont fontWithName:@"OpenSans-Bold" size:10]];
    [cell.buttonView setTag:[[categoryDictionary valueForKey:@"categoryID"] intValue]];
    [cell.buttonView addTarget:self action:@selector(viewbuttonClicked:) forControlEvents:UIControlEventTouchUpInside];

    //CATEGORY label

    NSString *categoryName =[[NSString stringWithFormat:@"%@",[categoryDictionary valueForKey:@"categoryNameen"]] uppercaseString];

    NSMutableAttributedString *attributedString;
    attributedString = [[NSMutableAttributedString alloc] initWithString:categoryName];

    [attributedString addAttribute:NSKernAttributeName
                            value:[NSNumber numberWithFloat:8.0]
                            range:NSMakeRange(0, [categoryName length])];

    [attributedString addAttribute:NSFontAttributeName
                            value:[UIFont fontWithName:@"OpenSans-Bold" size:19]
                            range:NSMakeRange(0, [categoryName length])];


    [cell.labelCategory setAttributedText:attributedString];

    cell.selectionStyle=UITableViewCellAccessoryNone;    
    //Set State    
    cell.ivCategoryBannerImage.alpha =0.1f;

    BOOL isAvailable = [[categoryDictionary valueForKey:@"isAvailable"] boolValue];
    BOOL userTappedDownload = [[categoryDictionary valueForKey:@"userTappedDownload"] boolValue];

    NSLog(@"isAvailable: %d", isAvailable);
    NSLog(@"userTappedDownload: %d", isAvailable);

    if (isAvailable && userTappedDownload)
    {
        cell.buttonView.hidden=NO;
        [cell.buttonView setTitle:@"VIEW" forState:UIControlStateNormal];
        cell.buttonViewDownload.hidden=YES;
        cell.ivCategoryBannerImage.alpha =1.0f;
        rect.size.width=208.0f;
    }
    else if(!isAvailable && !userTappedDownload)
    {
        rect.size.width=0.1f;
        [cell.buttonViewDownload setTitle:[NSString stringWithFormat:@"DOWNLOAD (%@ KB)",[categoryDictionary valueForKey:@"totalImagesSize"]] forState:0];            
    }
    else if(!isAvailable && userTappedDownload)
    {
        rect.size.width=[[categoryDictionary valueForKey:@"totalImagesAvailable"] intValue];
        [cell.buttonViewDownload setTitle:@"DOWNLOADING CONTENT" forState:UIControlStateNormal];
        cell.buttonViewDownload.userInteractionEnabled = NO;      
    }    
    return cell;
}

Answer 1

第五个单元格可能正在重复使用之前设置了 cell.buttonViewDownload.hidden=YES; 的单元格之一。

尝试将 cell.buttonViewDownload.hidden=NO; 添加到应显示下载按钮的分支。