的UITableViewCell滾動不與自定義單元格

Question

這種平穩是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:@"%@ &rarr; %@", thread.sender.FullName, recipients] dataUsingEncoding:NSUnicodeStringEncoding] options:@{ NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType } documentAttributes:nil error:nil]; 

      NSAttributedString *attrArrow = [[NSAttributedString alloc] initWithData:[[NSString stringWithFormat:@" &rarr; %@", 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; 
    } 
} 

我知道那巨大的代碼，但是這將是中斷平滑滾動？

Answer 1

我介紹了幾個假設：

• 您配置許多制約因素。這對平滑滾動是不利的。如果你的細胞很複雜，因此有許多限制 - >你可以看到顫抖的卷軸。
• 另外我可以看到你動態添加/刪除子視圖。你爲什麼這麼做？爲什麼不在init方法中配置標籤？
• 有時候shadow和cornerRadius會影響順暢的滾動。

我認爲在你的情況下主要問題 - 它的約束和動態添加/刪除視圖。