Question

当我滚动我的UITableView时，出于某种原因，单元格似乎相互绘制。如果我加载我的应用程序，单元格将显示如下：

enter image description here

在滚动此单元格并多次在屏幕上滚动时，它将开始显示如下：

enter image description here

正如你所看到的，我似乎无法解决的问题是错误的。有什么想法吗？

编辑：cellForRowAtIndexPath

static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
    }

    NSString *vaultsPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/Vaults"];

    NSString *dictionaryPath = [NSString stringWithFormat:@"%@/%@",
                                vaultsPath,
                                [self.vaults objectAtIndex:indexPath.row]];
    NSDictionary *dictionary = [NSDictionary dictionaryWithContentsOfFile:dictionaryPath];
    cell = [AHCellCreation createCellWithDictionary:dictionary Cell:cell];

    return cell;

AHCellCreation + createCellWithDictionary：Cell：

//General cell design, same every time
CAGradientLayer *gradient = [CAGradientLayer layer];
gradient.frame = CGRectMake(0, 0, 320, 82);
gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor colorWithHue:0 saturation:0 brightness:0.91 alpha:1] CGColor], (id)[[UIColor colorWithHue:0 saturation:0 brightness:0.85 alpha:1] CGColor], nil];
[cell.contentView.layer addSublayer:gradient];

UIView *topLine = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 1)];
topLine.backgroundColor = [UIColor colorWithHue:0 saturation:0 brightness:0.97 alpha:1.0];
[cell addSubview:topLine];

UIView *bottomLine = [[UIView alloc] initWithFrame:CGRectMake(0, 81, 320, 1)];
bottomLine.backgroundColor = [UIColor colorWithHue:0 saturation:0 brightness:0.64 alpha:1.0];
[cell addSubview:bottomLine];

//Preview Image
NSString *previewImageFilePath = [dictionary objectForKey:@"PreviewImage"];

UIImageView *previewImageView = [[UIImageView alloc] initWithFrame:CGRectMake(9, 9, 64, 64)];
previewImageView.image = [UIImage imageWithContentsOfFile:previewImageFilePath];
[cell addSubview:previewImageView];

//Creation date 
UILabel *createdOnLabel = [[UILabel alloc] init];
createdOnLabel.frame = CGRectMake(85, -5, 303, 41);
createdOnLabel.text = @"Created on";
createdOnLabel.backgroundColor = [UIColor clearColor];
createdOnLabel.textAlignment = UITextAlignmentLeft;
createdOnLabel.font = [UIFont systemFontOfSize:12];
createdOnLabel.textColor = [UIColor colorWithHue:0.59 saturation:0.29 brightness:0.47 alpha:1.0];
[cell addSubview:createdOnLabel];

NSDate *creationDate = [dictionary objectForKey:@"CreationDate"];
UILabel *creationDateLabel = [[UILabel alloc] initWithFrame:CGRectMake(85, 0, 303, 82)];
creationDateLabel.text = [AHCellCreation createReadableDateFromDate:creationDate];
creationDateLabel.backgroundColor = [UIColor clearColor];
creationDateLabel.textAlignment = UITextAlignmentLeft;
creationDateLabel.font = [UIFont boldSystemFontOfSize:28];
creationDateLabel.textColor = [UIColor colorWithHue:0.59 saturation:0.29 brightness:0.47 alpha:1.0];
[cell addSubview:creationDateLabel];

//Opening date
NSDate *notificationDate = [dictionary objectForKey:@"NotificationDate"];

NSDate *earliest = [notificationDate earlierDate:[NSDate date]];
BOOL notificationPassed;
if (earliest == [NSDate date]) {
    notificationPassed = YES;
}
else {
    notificationPassed = NO;
}

UILabel *notificationDateLabel = [[UILabel alloc] initWithFrame:CGRectMake(85, 47, 303, 41)];
if (notificationPassed == NO) {
    notificationDateLabel.text = @"To be opened";
}
else {
    notificationDateLabel.text = @"Opened on";
}
notificationDateLabel.backgroundColor = [UIColor clearColor];
notificationDateLabel.textAlignment = UITextAlignmentLeft;
notificationDateLabel.font = [UIFont systemFontOfSize:12];
notificationDateLabel.textColor = [UIColor colorWithHue:0.59 saturation:0.29 brightness:0.47 alpha:1.0];
[cell addSubview:notificationDateLabel];

UILabel *notificationDateLabel2 = [[UILabel alloc] init];
notificationDateLabel2.frame = CGRectMake(164, 47, 303, 41);
notificationDateLabel2.text = [AHCellCreation createReadableDateFromDate:notificationDate];
notificationDateLabel2.backgroundColor = [UIColor clearColor];
notificationDateLabel2.textAlignment = UITextAlignmentLeft;
notificationDateLabel2.font = [UIFont boldSystemFontOfSize:12];
notificationDateLabel2.textColor = [UIColor colorWithHue:0.59 saturation:0.29 brightness:0.47 alpha:1.0];
[cell addSubview:notificationDateLabel2];


return cell;

Answer 1

每次显示时，你只是在你的手机中添加越来越多的UILabel等！

您需要跟踪要添加到单元格中的所有内容，以确保只添加一次！有几种方法可以做到这一点，但我建议你自己继承UITableViewCell

例如，以下是使createdOnLabel正常工作的代码：

@interface AHTableViewCell : UITAbleViewCell {
    UILabel *createdOnLabel;
}

@end

@implementation AHTableViewCell

@end

然后，您的cellForRowAtIndexPath代码变为

AHTableViewCell *cell = (AHTableViewCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[AHTableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
    }

，您的创建代码变为：

//Creation date
UILabel *createdOnLabel = [cell createdOnLabel];
if (nil == createdOnLabel) {
    createdOnLabel = [[UILabel alloc] init];
    createdOnLabel.frame = CGRectMake(85, -5, 303, 41);
    createdOnLabel.backgroundColor = [UIColor clearColor];
    createdOnLabel.textAlignment = UITextAlignmentLeft;
    createdOnLabel.font = [UIFont systemFontOfSize:12];
    createdOnLabel.textColor = [UIColor colorWithHue:0.59 saturation:0.29 brightness:0.47 alpha:1.0];
    [cell addSubview:createdOnLabel];
    [cell setCreatedOnLabel:createdOnLabel];
}
createdOnLabel.text = @"Created on";

所以，第一次创建单元格时，就会创建标签。你要求创建单元格的所有其他时间，你检查标签是否已经存在，如果是，只需更新它的文本。

Answer 2

我想你一直在为单元格的内容视图添加一些视图。只有在看到代码后才能找到解决方案。

修改

实际上我已经为你发布的代码提供了解决方案。但我也建议按照deanWombourne的建议继承UITableViewCell。

是的，我的猜测是正确的。

首先，按如下方式制作cellForRowAtIndexPath。

static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; NSString *vaultsPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/Vaults"]; NSString *dictionaryPath = [NSString stringWithFormat:@"%@/%@", vaultsPath, [self.vaults objectAtIndex:indexPath.row]]; NSDictionary *dictionary = [NSDictionary dictionaryWithContentsOfFile:dictionaryPath]; cell = [AHCellCreation createCellWithDictionary:dictionary Cell:cell]; } else { NSString *vaultsPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/Vaults"]; NSString *dictionaryPath = [NSString stringWithFormat:@"%@/%@", vaultsPath, [self.vaults objectAtIndex:indexPath.row]]; NSDictionary *dictionary = [NSDictionary dictionaryWithContentsOfFile:dictionaryPath]; cell = [AHCellCreation updateCellWithDictionary:dictionary Cell:cell]; } return cell;

AHCellCreation + createCellWithDictionary：Cell：

//General cell design, same every time CAGradientLayer *gradient = [CAGradientLayer layer]; gradient.frame = CGRectMake(0, 0, 320, 82); gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor colorWithHue:0 saturation:0 brightness:0.91 alpha:1] CGColor], (id)[[UIColor colorWithHue:0 saturation:0 brightness:0.85 alpha:1] CGColor], nil]; [cell.contentView.layer addSublayer:gradient]; UIView *topLine = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 1)]; topLine.tag = 100; topLine.backgroundColor = [UIColor colorWithHue:0 saturation:0 brightness:0.97 alpha:1.0]; [cell addSubview:topLine]; UIView *bottomLine = [[UIView alloc] initWithFrame:CGRectMake(0, 81, 320, 1)]; bottomLine.tag = 101; bottomLine.backgroundColor = [UIColor colorWithHue:0 saturation:0 brightness:0.64 alpha:1.0]; [cell addSubview:bottomLine]; //Preview Image NSString *previewImageFilePath = [dictionary objectForKey:@"PreviewImage"]; UIImageView *previewImageView = [[UIImageView alloc] initWithFrame:CGRectMake(9, 9, 64, 64)]; previewImageView.tag = 102; previewImageView.image = [UIImage imageWithContentsOfFile:previewImageFilePath]; [cell addSubview:previewImageView]; //Creation date UILabel *createdOnLabel = [[UILabel alloc] init]; createdOnLabel.tag = 103; createdOnLabel.frame = CGRectMake(85, -5, 303, 41); createdOnLabel.text = @"Created on"; createdOnLabel.backgroundColor = [UIColor clearColor]; createdOnLabel.textAlignment = UITextAlignmentLeft; createdOnLabel.font = [UIFont systemFontOfSize:12]; createdOnLabel.textColor = [UIColor colorWithHue:0.59 saturation:0.29 brightness:0.47 alpha:1.0]; [cell addSubview:createdOnLabel]; NSDate *creationDate = [dictionary objectForKey:@"CreationDate"]; UILabel *creationDateLabel = [[UILabel alloc] initWithFrame:CGRectMake(85, 0, 303, 82)]; creationDateLabel.tag = 104; creationDateLabel.text = [AHCellCreation createReadableDateFromDate:creationDate]; creationDateLabel.backgroundColor = [UIColor clearColor]; creationDateLabel.textAlignment = UITextAlignmentLeft; creationDateLabel.font = [UIFont boldSystemFontOfSize:28]; creationDateLabel.textColor = [UIColor colorWithHue:0.59 saturation:0.29 brightness:0.47 alpha:1.0]; [cell addSubview:creationDateLabel]; //Opening date NSDate *notificationDate = [dictionary objectForKey:@"NotificationDate"]; NSDate *earliest = [notificationDate earlierDate:[NSDate date]]; BOOL notificationPassed; if (earliest == [NSDate date]) { notificationPassed = YES; } else { notificationPassed = NO; } UILabel *notificationDateLabel = [[UILabel alloc] initWithFrame:CGRectMake(85, 47, 303, 41)]; notificationDateLabel.tag = 105; if (notificationPassed == NO) { notificationDateLabel.text = @"To be opened"; } else { notificationDateLabel.text = @"Opened on"; } notificationDateLabel.backgroundColor = [UIColor clearColor]; notificationDateLabel.textAlignment = UITextAlignmentLeft; notificationDateLabel.font = [UIFont systemFontOfSize:12]; notificationDateLabel.textColor = [UIColor colorWithHue:0.59 saturation:0.29 brightness:0.47 alpha:1.0]; [cell addSubview:notificationDateLabel]; UILabel *notificationDateLabel2 = [[UILabel alloc] init]; notificationDateLabel.tag = 106; notificationDateLabel2.frame = CGRectMake(164, 47, 303, 41); notificationDateLabel2.text = [AHCellCreation createReadableDateFromDate:notificationDate]; notificationDateLabel2.backgroundColor = [UIColor clearColor]; notificationDateLabel2.textAlignment = UITextAlignmentLeft; notificationDateLabel2.font = [UIFont boldSystemFontOfSize:12]; notificationDateLabel2.textColor = [UIColor colorWithHue:0.59 saturation:0.29 brightness:0.47 alpha:1.0]; [cell addSubview:notificationDateLabel2]; return cell;

AHCellCreation + updateCellWithDictionary：Cell：

UIView *topLine = (UIView*)[cell viewWithTag:100]; topLine.backgroundColor = [UIColor colorWithHue:0 saturation:0 brightness:0.97 alpha:1.0]; UIView *bottomLine = (UIView*)[cell viewWithTag:101]; bottomLine.backgroundColor = [UIColor colorWithHue:0 saturation:0 brightness:0.64 alpha:1.0]; //Preview Image NSString *previewImageFilePath = [dictionary objectForKey:@"PreviewImage"]; UIImageView *previewImageView = (UIImageView*)[cell viewWithTag:102]; previewImageView.image = [UIImage imageWithContentsOfFile:previewImageFilePath]; //Creation date UILabel *createdOnLabel = (UILabel*)[cell viewWithTag:103]; createdOnLabel.text = @"Created on"; NSDate *creationDate = [dictionary objectForKey:@"CreationDate"]; UILabel *creationDateLabel = (UILabel*)[cell viewWithTag:104]; creationDateLabel.text = [AHCellCreation createReadableDateFromDate:creationDate]; //Opening date NSDate *notificationDate = [dictionary objectForKey:@"NotificationDate"]; NSDate *earliest = [notificationDate earlierDate:[NSDate date]]; BOOL notificationPassed; if (earliest == [NSDate date]) { notificationPassed = YES; } else { notificationPassed = NO; } UILabel *notificationDateLabel = (UILabel*)[cell viewWithTag:105]; if (notificationPassed == NO) { notificationDateLabel.text = @"To be opened"; } else { notificationDateLabel.text = @"Opened on"; } UILabel *notificationDateLabel2 = (UILabel*)[cell viewWithTag:106]; notificationDateLabel2.text = [AHCellCreation createReadableDateFromDate:notificationDate]; return cell;

Answer 3

@ Gomathi的直觉是正确的。你在这里找到一个回收的细胞：

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

此单元格已包含所有视图。然后，您将再次添加视图。当您从dequeueReusableCellWithIdentifier:返回一个单元格时，您应该重新配置它（更改文本和图像字段的值），而不是从头开始重建它。这是可重复使用细胞的重点。请务必阅读Table View Programming Guide了解完整详情。

Answer 4

单元重用的重点是仅在未从dequeueReusableCellWithIdentifier返回单元格时才在UITableViewCell中分配任何视图。 allocs减慢了应该滚动顺畅的tableView中的滚动。你基本上需要做的是，当你出局时没有得到你需要的所有视图。当你收到一个出列的单元格时，你应该只是从某个模型对象或类似物体上设置状态。

UITableView在滚动时重复单元格

4 个答案: