UITableViewCell 使用自定义单元格滚动不平滑
Posted
技术标签:
【中文标题】UITableViewCell 使用自定义单元格滚动不平滑【英文标题】：UITableViewCell scroll not smooth with custom cell 【发布时间】：2016-11-07 14:25:21 【问题描述】：这是cellForRowAtIndexPath：
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
MessageDetailCell *cell;
@try
if(indexPath != nil && indexPath.row < arrMessages.count)
cell = [tableView dequeueReusableCellWithIdentifier:@"MessageDetailCell"];
if (cell == nil)
NSArray *topLevelObjects = [[NSBundle mainBundle] loadNibNamed:@"MessageDetailCell" owner:self options:nil];
cell = [topLevelObjects objectAtIndex:0];
cell.selectionStyle = UITableViewCellSelectionStyleNone;
cell.accessoryType = UITableViewCellAccessoryNone;
if ([cell respondsToSelector:@selector(layoutMargins)])
cell.layoutMargins = UIEdgeInsetsZero;
cell.preservesSuperviewLayoutMargins = false;
else
NSArray *arr = [cell.contentView subviews];
for(int i=0; i<[arr count]; i++)
UIView *view = [arr objectAtIndex:i];
[view removeFromSuperview];
cell.tag = indexPath.row;
cell.selectionStyle = UITableViewCellSelectionStyleNone;
cell.accessoryType = UITableViewCellAccessoryNone;
MessageThread *thread = [arrMessages objectAtIndex:indexPath.row];
float xAxis = 10.0;
float yAxis = 10.0;
float imageDimention = 40;
float fontSize = 20;
NSLog(@"");
if(indexPath.row == 0)
xAxis = 10;
imageDimention = 40;
fontSize = 20;
cell.imgUserWidthConstraint.constant = 40;
cell.imgUserHeightConstraint.constant = 40;
cell.lblContentLeftConstraint.constant = 64;
cell.btnReplyLeftConstraint.constant = 64;
else
xAxis = 32 * thread.ReplyLevel;
imageDimention = 32;
fontSize = 17;
cell.imgUserWidthConstraint.constant = 32;
cell.imgUserHeightConstraint.constant = 32;
cell.lblContentLeftConstraint.constant = 110;
cell.btnReplyLeftConstraint.constant = 110;
if(![thread.sender.Image isEqual:@""] && ![thread.sender.Image.lowercaseString containsString:@"default"])
[self createImage:CGRectMake(xAxis, yAxis, imageDimention, imageDimention) cell:cell messageThread:thread];
else
UILabel *lblLetter = [[UILabel alloc]initWithFrame:CGRectMake(xAxis, yAxis, imageDimention, imageDimention)];
lblLetter.layer.cornerRadius = lblLetter.frame.size.width / 2;
lblLetter.layer.borderColor = [[UIColor blackColor] CGColor];
lblLetter.layer.borderWidth = 0.8;
lblLetter.layer.masksToBounds = YES;
lblLetter.backgroundColor = [UIColor colorWithRed:239.0/255.0 green:239.0/255.0 blue:239.0/255.0 alpha:1.0];
lblLetter.text = [thread.sender.FirstName substringToIndex:1];
lblLetter.font = [UIFont boldSystemFontOfSize:fontSize];
lblLetter.textAlignment = NSTextAlignmentCenter;
lblLetter.textColor = [UIColor blackColor];
[cell.contentView addSubview:lblLetter];
cell.imgUserLeftConstraint.constant = xAxis;
xAxis = 80;
NSString *recipients = @"";
for(Recipient *rp in thread.Recipients)
recipients = [recipients stringByAppendingString:[NSString stringWithFormat:@"%@, ", rp.Name]];
recipients = [recipients substringToIndex:recipients.length - 2];
NSAttributedString * attrUserText;
attrUserText = [[NSAttributedString alloc] initWithData:[[NSString stringWithFormat:@"%@ → %@", thread.sender.FullName, recipients] dataUsingEncoding:NSUnicodeStringEncoding] options:@ NSDocumentTypeDocumentAttribute: NShtmlTextDocumentType documentAttributes:nil error:nil];
NSAttributedString *attrArrow = [[NSAttributedString alloc] initWithData:[[NSString stringWithFormat:@" → %@", recipients] dataUsingEncoding:NSUnicodeStringEncoding] options:@ NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType documentAttributes:nil error:nil];
NSMutableAttributedString *string = [[NSMutableAttributedString alloc]initWithAttributedString:attrUserText];
int firstHalf = (int)thread.sender.FullName.length;
int secondHalf = (int)attrArrow.length;
[string addAttribute:NSForegroundColorAttributeName value:[UIColor lightGrayColor] range:NSMakeRange(firstHalf,secondHalf + 1)];
[string addAttribute:NSForegroundColorAttributeName value:[UIColor blackColor] range:NSMakeRange(0,firstHalf)];
cell.lblUsers.attributedText = string;
cell.lblUsers.textAlignment = NSTextAlignmentLeft;
cell.lblUsers.font = [UIFont boldSystemFontOfSize:15];
cell.lblUsers.numberOfLines = 0;
cell.lblDate.text = [self returnDate:thread.CreatedOn];
cell.lblDateTopConstraint.constant = 10;
cell.lblDate.textAlignment = NSTextAlignmentLeft;
cell.lblDate.font = [UIFont systemFontOfSize:12];
cell.lblContent.tag = (int)indexPath.row;
cell.lblContent.backgroundColor = [UIColor clearColor];
cell.lblContent.textColor = [UIColor blackColor];
cell.lblContent.textAlignment = NSTextAlignmentLeft;
cell.lblContent.font = [UIFont systemFontOfSize:14];
cell.lblContent.text = thread.MessageContent;
cell.lblContent.dataDetectorTypes = UIDataDetectorTypeLink;
cell.lblContent.dataDetectorTypes = UIDataDetectorTypeAll;
cell.lblContent.scrollEnabled = NO;
cell.lblContent.editable = NO;
cell.lblContent.selectable = YES;
cell.lblContent.contentInset = UIEdgeInsetsMake(0, -4, 0, 0);
[cell.lblContent layoutIfNeeded];
//
yAxis = yAxis + 30;
float yAxisDocAttachment = 0;
cell.viewAttachmentHeightConstraint.constant = 0;
BOOL isDoc = NO;
BOOL isImage = NO;
if(thread.attachments.count > 0)
for(MessageAttachment *msgDoc in thread.attachments)
if(![msgDoc.Type isEqual:@"Image"])
isDoc = YES;
cell.viewAttachmentCollection.hidden = NO;
cell.viewAttachmentTopConstraint.constant = 10;
if((int)indexPath.row != 0)
cell.viewAttachmentLeftConstraint.constant = xAxis - 16;
else
cell.viewAttachmentLeftConstraint.constant = xAxis;
UIView *viewAttachment = [[UIView alloc]initWithFrame:CGRectMake(0, yAxisDocAttachment, self.view.frame.size.width - cell.lblContent.frame.origin.x - 50, 80)];
viewAttachment.backgroundColor = [UIColor colorWithRed:234.0/255.0 green:234.0/255.0 blue:234.0/255.0 alpha:1.0];
viewAttachment.tag = indexPath.row;
viewAttachment.accessibilityIdentifier = msgDoc.Url;
viewAttachment.accessibilityLabel = msgDoc.Name;
[cell.viewAttachmentCollection addSubview:viewAttachment];
UIImageView *imgAttachment = [[UIImageView alloc]initWithFrame:CGRectMake(10, 10, 52, 60)];
imgAttachment.image = [UIImage imageNamed:@"document.png"];
[viewAttachment addSubview:imgAttachment];
UILabel *lblFileName = [[UILabel alloc]initWithFrame:CGRectMake(65, 5, viewAttachment.frame.size.width - 65, 22)];
lblFileName.backgroundColor = [UIColor clearColor];
lblFileName.text = msgDoc.Name;
lblFileName.text = [lblFileName.text stringByReplacingOccurrencesOfString:@"%20" withString:@" "];
lblFileName.textAlignment = NSTextAlignmentLeft;
lblFileName.font = [UIFont systemFontOfSize:10];
lblFileName.numberOfLines = 0;
[viewAttachment addSubview:lblFileName];
[lblFileName sizeToFit];
UILabel *lblFileType = [[UILabel alloc]initWithFrame:CGRectMake(65, 30, viewAttachment.frame.size.width - 65, 20)];
lblFileType.backgroundColor = [UIColor clearColor];
lblFileType.text = msgDoc.Name;
lblFileType.textAlignment = NSTextAlignmentLeft;
lblFileType.font = [UIFont systemFontOfSize:10];
[viewAttachment addSubview:lblFileName];
UILabel *lblDownload = [[UILabel alloc]initWithFrame:CGRectMake(65, 53, viewAttachment.frame.size.width - 65, 20)];
lblDownload.backgroundColor = [UIColor clearColor];
lblDownload.text = NSLocalizedString(@"click_to_download", nil);
lblDownload.textAlignment = NSTextAlignmentLeft;
lblDownload.font = [UIFont systemFontOfSize:10];
[viewAttachment addSubview:lblDownload];
UITapGestureRecognizer *gestureAttachment = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleAttachmentGesture:)];
[viewAttachment addGestureRecognizer:gestureAttachment];
yAxis = yAxis + 90;
yAxisDocAttachment = yAxisDocAttachment + 90;
cell.viewAttachmentHeightConstraint.constant = cell.viewAttachmentHeightConstraint.constant + 90;
cell.viewImageHeightConstraint.constant = 0;
if(indexPath.row != 0)
cell.viewImageLeftConstraint.constant = xAxis - 16;
else
cell.viewImageLeftConstraint.constant = xAxis;
for(MessageAttachment *msgDoc in thread.attachments)
if([msgDoc.Type isEqual:@"Image"])
isImage = YES;
cell.viewImageCollection.hidden = NO;
cell.viewImageTopConstraint.constant = 10;
cell.btnReplyTopConstraint.constant = 10;
[self createAttachmentImage:CGRectMake(xAxis, cell.viewImageHeightConstraint.constant + 10, self.view.frame.size.width - xAxis - 5, 480) cell:cell message:msgDoc indexPath:indexPath];
cell.viewImageHeightConstraint.constant = cell.viewImageHeightConstraint.constant + 5;
if(!isDoc)
cell.viewAttachmentCollection.hidden = YES;
cell.viewAttachmentHeightConstraint.constant = 0;
cell.viewAttachmentTopConstraint.constant = 0;
if(!isImage)
cell.viewImageCollection.hidden = YES;
cell.viewImageHeightConstraint.constant = 0;
cell.viewImageTopConstraint.constant = 0;
[cell.btnReplyCell setTitle:[NSString stringWithFormat:@"%@ %@", NSLocalizedString(@"reply", nil),thread.sender.FirstName] forState:UIControlStateNormal];
[cell.btnReplyCell setTitle:[NSString stringWithFormat:@"%@ %@", NSLocalizedString(@"reply", nil),thread.sender.FirstName] forState:UIControlStateDisabled];
[cell.btnReplyCell setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
[cell.btnReplyCell setTitleColor:[UIColor colorWithRed:199.0/255.0 green:192.0/255.0 blue:193.0/255.0 alpha:1.0] forState:UIControlStateDisabled];
if(thread.sender.SenderId != [[NSString stringWithFormat:@"%@", [[NSUserDefaults standardUserDefaults]objectForKey:@"UserId"]] intValue])
cell.btnReplyTopConstraint.constant = 10;
cell.btnReplyHeightConstraint.constant = 30;
cell.btnReplyBottomConstraint.constant = 12;
cell.btnReplyCell.titleLabel.textAlignment = NSTextAlignmentCenter;
cell.btnReplyCell.layer.cornerRadius = 7;
cell.btnReplyCell.tag = (int)indexPath.row;
cell.btnReplyCell.backgroundColor = [UIColor whiteColor];
cell.btnReplyCell.layer.borderColor = [[UIColor blackColor] CGColor];
cell.btnReplyCell.layer.borderWidth = 0.7;
cell.btnReplyCell.accessibilityIdentifier = [NSString stringWithFormat:@"%i", (int)arrBtnReply.count];
cell.btnReplyCell.titleLabel.font = [UIFont systemFontOfSize:12];
[cell.btnReplyCell addTarget:self action:@selector(replyTapped:) forControlEvents:UIControlEventTouchUpInside];
yAxis = yAxis + 20;
cell.btnReplyCell.accessibilityLabel = [NSString stringWithFormat:@"%f", yAxis];
cell.btnReplyCell.enabled = YES;
cell.btnReplyTopConstraint.constant = 10;
else
cell.btnReplyTopConstraint.constant = 10;
cell.btnReplyBottomConstraint.constant = 0;
cell.btnReplyCell.hidden = YES;
cell.btnReplyHeightConstraint.constant = 0;
cell.btnReplyCell.layer.cornerRadius = 7;
cell.btnReplyCell.backgroundColor = [UIColor colorWithRed:224.0/255.0 green:224.0/255.0 blue:224.0/255.0 alpha:1.0];
cell.btnReplyCell.enabled = NO;
[cell updateConstraintsIfNeeded];
[cell setNeedsLayout];
[cell layoutIfNeeded];
return cell;
@catch (NSException *exception)
return cell;
我知道那巨大的代码，但是什么会打断平滑滚动？
【问题讨论】：
你能附上这个单元格的截图吗？ 【参考方案1】：我描述了一些假设：
您配置了许多约束。这不利于平滑滚动。如果您的单元格很复杂，因此有很多限制 -> 您可以看到抽动的滚动条。 我还可以看到您动态添加/删除子视图。你为什么这么做？为什么不在init方法中配置label呢？ 有时shadow 和cornerRadius 会影响平滑滚动。
我认为你的主要问题是约束和动态添加/删除视图。
【讨论】：
以上是关于UITableViewCell 使用自定义单元格滚动不平滑的主要内容，如果未能解决你的问题，请参考以下文章
自定义 UITableViewCell 前导对齐到右细节单元格
在 iOS 中使用自定义单元格时无法查看 UITableViewCell
错误：无法使用自定义单元格类设置 UITableViewCell 标签和图像！只能加载单元格样式的数据：字幕不是自定义的