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UITableView:`tableView:cellForRowAtIndexPath:`未对所有行调用
原标题：UITableView: `tableView:cellForRowAtIndexPath:` not called for all rows

我创建了一个UITableView，有4个部分和3行，总共12行。但是

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath

The above method only gets called for 9 times instead of 12 times. Why this happening? My 4th section is not getting constructed but my 1st section gets duplicated as 4th section.

请参阅下面的代码

@interface MainViewController : UITableViewController<UITextFieldDelegate,UITableViewDelegate,UITableViewDataSource>
 {
}
@end


// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad 
{
  CGRect frameRect = CGRectMake(0,0,320,460);

  UITableView *tableView = [[UITableView alloc] initWithFrame:frameRect   
  style:UITableViewStyleGrouped];
  tableView.delegate = self;
  tableView.dataSource = self;  
  tableView.backgroundColor = [UIColor purpleColor];
  tableView.scrollEnabled = YES;

  self.view = tableView;
  [tableView release];

  [super viewDidLoad];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    // Return the number of rows in the section.
    return 3;
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    // Return the number of sections.
    return 4;
}

// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
{
     NSLog(@"CELL IS NIL %i", indexPath.section);

  static NSString *CellIdentifier = @"Cell";
  UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
  if (cell == nil)
  {
    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];

      if (indexPath.section == 0)
      {
          if(indexPath.row == 0)
          {
              cell.text = @"Tmail";

              UITextField *aField = [[UITextField alloc]initWithFrame:CGRectMake(100,10,200,40)];
              aField.placeholder = @"Mandatory";
              aField.delegate = self;
              aField.textColor = [UIColor blackColor];
              [cell addSubview:aField];
              [aField release];
          }
          else if ( indexPath.row == 1 )
          {
              cell.text = @"English";
              UITextField *aField = [[UITextField alloc]initWithFrame:CGRectMake(100,10,200,40)];
              aField.placeholder = @"Mandatory";
              aField.delegate = self;
              aField.textColor = [UIColor blackColor];
              [cell addSubview:aField];
              [aField release];
          }
          else
          {
              cell.text = @"Hindi";
              UITextField *aField = [[UITextField alloc]initWithFrame:CGRectMake(100,10,200,40)];
              aField.placeholder = @"Mandatory";
              aField.delegate = self;
              aField.textColor = [UIColor blackColor];
              [cell addSubview:aField];
              [aField release];
          }
      }
      else if (indexPath.section == 1)
      {
          if(indexPath.row == 0)
          {
              cell.text = @"Street";

              UITextField *aField = [[UITextField alloc]initWithFrame:CGRectMake(100,10,200,40)];
              aField.placeholder = @"Mandatory";
              aField.delegate = self;
              aField.textColor = [UIColor blackColor];
              [cell addSubview:aField];
              [aField release];
          }
          else if ( indexPath.row == 1 )
          {
              cell.text = @"City";
              UITextField *aField = [[UITextField alloc]initWithFrame:CGRectMake(100,10,200,40)];
              aField.placeholder = @"Mandatory";
              aField.delegate = self;
              aField.textColor = [UIColor blackColor];
              [cell addSubview:aField];
              [aField release];
          }
          else
          {
              cell.text = @"State";
              UITextField *aField = [[UITextField alloc]initWithFrame:CGRectMake(100,10,200,40)];
              aField.placeholder = @"Mandatory";
              aField.delegate = self;
              aField.textColor = [UIColor blackColor];
              [cell addSubview:aField];
              [aField release];
          }
      }
      else if (indexPath.section == 2)
      {
          if(indexPath.row == 0)
          {
              cell.text = @"Salem";

              UITextField *aField = [[UITextField alloc]initWithFrame:CGRectMake(100,10,200,40)];
              aField.placeholder = @"Mandatory";
              aField.delegate = self;
              aField.textColor = [UIColor blackColor];
              [cell addSubview:aField];
              [aField release];
          }
          else if ( indexPath.row == 1 )
          {
              cell.text = @"Samalpatti";
              UITextField *aField = [[UITextField alloc]initWithFrame:CGRectMake(100,10,200,40)];
              aField.placeholder = @"Mandatory";
              aField.delegate = self;
              aField.textColor = [UIColor blackColor];
              [cell addSubview:aField];
              [aField release];
          }
          else
          {
              cell.text = @"Chennai";
              UITextField *aField = [[UITextField alloc]initWithFrame:CGRectMake(100,10,200,40)];
              aField.placeholder = @"Mandatory";
              aField.delegate = self;
              aField.textColor = [UIColor blackColor];
              [cell addSubview:aField];
              [aField release];
          }
      }

      else if (indexPath.section == 3)
      {
          if(indexPath.row == 0)
          {
              cell.text = @"NOKIA";
              UITextField *aField = [[UITextField alloc]initWithFrame:CGRectMake(100,10,200,40)];
              aField.placeholder = @"Mandatory";
              aField.delegate = self;
              aField.textColor = [UIColor blackColor];
              [cell addSubview:aField];
              [aField release];
          }
          else if ( indexPath.row == 1)
          {
              cell.text = @"SAMSUNG";
              UITextField *aField = [[UITextField alloc]initWithFrame:CGRectMake(100,10,200,40)];
              aField.placeholder = @"Mandatory";
              aField.delegate = self;
              aField.textColor = [UIColor blackColor];
              [cell addSubview:aField];
              [aField release];
          }
          else
          {
              cell.text = @"SONY";
              UITextField *aField = [[UITextField alloc]initWithFrame:CGRectMake(100,10,200,40)];
              aField.placeholder = @"Mandatory";
              aField.delegate = self;
              aField.textColor = [UIColor blackColor];
              [cell addSubview:aField];
              [aField release];
          }
      }
   }

  return cell;
}

最佳回答

实际上，当你滚动时，会创建其他行，以防你有更多的行，所以认为你需要这样写代码，

编辑一个

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
    {
         NSLog(@"CELL IS NIL %i", indexPath.section);

      static NSString *CellIdentifier = @"Cell";
if (cell == nil) 
    {

        CGRect CellFrame = CGRectMake(0, 0, 300, 70);
        cell = [[[UITableViewCell alloc] initWithFrame:CellFrame reuseIdentifier:CellIdentifier] autorelease];
        CGRect labLabelFrame = CGRectMake(5, 5, 250, 40);
        UILabel *lblTemp;

        lblTemp = [[UILabel alloc] initWithFrame:labLabelFrame];
        lblTemp.tag = 1;
        [cell.contentView addSubview:lblTemp];
        [lblTemp release];

        CGRect textFieldFrame= CGRectMake(200, 5, 120, 30);

        UITextField *txt=[[UITextField alloc] initWithFrame:textFieldFrame];
        text.tag=2;
        [cell.contentView addSubview:txt];
        [txt release];

    }
     UILabel *cellLabel = (UILabel *)[cell viewWithTag:1];
      UITextField *aField=(UITextField *)[cell viewWithTag:2];

    aField.text=@"";
    aField.placeholder=@"";
if (indexPath.section == 0)
              {
                  if(indexPath.row == 0)
                  {
                      cellLabel.text = @"Tmail";


                      aField.placeholder = @"Mandatory";
                      aField.delegate = self;
                      aField.textColor = [UIColor blackColor];

                  }
                  else if ( indexPath.row == 1 )
                  {
                      cellLabel.text = @"English";

                      aField.placeholder = @"Mandatory";
                      aField.delegate = self;
                      aField.textColor = [UIColor blackColor];


                  }
                  else
                  {
                      cellLabel.text = @"Hindi";

                      aField.placeholder = @"Mandatory";
                      aField.delegate = self;
                      aField.textColor = [UIColor blackColor];


                  }
              }
              else if (indexPath.section == 1)
              {
                  if(indexPath.row == 0)
                  {
                      cellLabel.text = @"Street";


                      aField.placeholder = @"Mandatory";
                      aField.delegate = self;
                      aField.textColor = [UIColor blackColor];

                  }
                  else if ( indexPath.row == 1 )
                  {
                      cellLabel.text = @"City";

                      aField.placeholder = @"Mandatory";
                      aField.delegate = self;
                      aField.textColor = [UIColor blackColor];


                  }
                  else
                  {
                      cellLabel.text = @"State";

                      aField.placeholder = @"Mandatory";
                      aField.delegate = self;
                      aField.textColor = [UIColor blackColor];

                  }
              }
              else if (indexPath.section == 2)
              {
                  if(indexPath.row == 0)
                  {
                      cellLabel.text = @"Salem";
                      aField.placeholder = @"Mandatory";
                      aField.delegate = self;
                      aField.textColor = [UIColor blackColor];

                  }
                  else if ( indexPath.row == 1 )
                  {
                      cellLabel.text = @"Samalpatti";

                      aField.placeholder = @"Mandatory";
                      aField.delegate = self;
                      aField.textColor = [UIColor blackColor];


                  }
                  else
                  {
                      cellLabel.text = @"Chennai";

                      aField.placeholder = @"Mandatory";
                      aField.delegate = self;
                      aField.textColor = [UIColor blackColor];


                  }
              }

              else if (indexPath.section == 3)
              {
                  if(indexPath.row == 0)
                  {
                      cellLabel.text = @"NOKIA";

                      aField.placeholder = @"Mandatory";
                      aField.delegate = self;
                      aField.textColor = [UIColor blackColor];

                  }
                  else if ( indexPath.row == 1)
                  {
                      cellLabel.text = @"SAMSUNG";

                      aField.placeholder = @"Mandatory";
                      aField.delegate = self;
                      aField.textColor = [UIColor blackColor];


                  }
                  else
                  {
                      cellLabel.text = @"SONY";

                      aField.placeholder = @"Mandatory";
                      aField.delegate = self;
                      aField.textColor = [UIColor blackColor];

                  }
              }


          return cell;
        }
时间：2011-02-16 05:08:42
问题回答

代码的问题是：

1） 细胞正在被重复使用。但是您添加为子视图的文本字段并没有被删除！

2） 每当调用cellforRowAtIndex时，每次都会添加文本字段。但您忘记了您已经添加了一个文本字段，但尚未将其删除。

  • This is the reason for overlapping.

Solution: Subclass the UITableViewCell and add textfield in its initWithFrame method and pass the data to that cell. This will solve your problem and also this will reduce your cellForRowAtIndex method length.

Sample code: CustomCell.h: 

#import <UIKit/UIKit.h>

@class contactr;
@interface CustomTableCell : UITableViewCell 
{
    UITextField *mTextField;
}
@property(nonatomic , retain) UITextField *textField;

@end

自定义单元格.m:

#import "CustomTableCell.h"
@synthesize textField = mTextField;
- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier 
{
    self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
    if (self) 
    {       
        UITextField *textField = [[UITextField alloc]initWithFrame:CGRectMake(100,10,200,40)];

        self.textField = textField;
        [textField release];
        [self addSubview:self.textField];

    }
    return self;
}

- (void)dealloc 
{
    self.textfield = nil;
    [super dealloc];
}


@end

将此类用作tableViewCell。

您的cellForRowAtIndex必须是：

// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
{
     NSLog(@"CELL IS NIL %i", indexPath.section);

  static NSString *CellIdentifier = @"Cell";
  CustomTableCell *cell = (CustomTableCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
  if (cell == nil)
  {


    cell = [[[CustomTableCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];

   }
 cell.textField.placeholder = @"";
 cell.textField.text = @"";
      if (indexPath.section == 0)
      {
          if(indexPath.row == 0)
          {
              cell.text = @"Tmail";
              cell.textField.placeholder = @"Mandatory";
              cell.textField.delegate = self;
          }
          else if ( indexPath.row == 1 )
          {
              cell.text = @"English";
              cell.textField.placeholder = @"Mandatory";
              cell.textField.delegate = self;
          }
          else
          {
              cell.text = @"Hindi";
              cell.textField.placeholder = @"Mandatory";
              cell.textField.delegate = self;
          }
      }
      else if (indexPath.section == 1)
      {
          if(indexPath.row == 0)
          {
              cell.text = @"Street";
              cell.textField.placeholder = @"Mandatory";
              cell.textField.delegate = self;
          }
          else if ( indexPath.row == 1 )
          {
              cell.text = @"City";
              cell.textField.placeholder = @"Mandatory";
              cell.textField.delegate = self;
          }
          else
          {
              cell.text = @"State";
              cell.textField.placeholder = @"Mandatory";
              cell.textField.delegate = self;

          }
      }
      else if (indexPath.section == 2)
      {
          if(indexPath.row == 0)
          {
              cell.text = @"Salem";

              cell.textField.placeholder = @"Mandatory";
              cell.textField.delegate = self;
          }
          else if ( indexPath.row == 1 )
          {
              cell.text = @"Samalpatti";
              cell.textField.placeholder = @"Mandatory";
              cell.textField.delegate = self;
              cell.textField.textColor = [UIColor blackColor];

          }
          else
          {
              cell.text = @"Chennai";
              cell.textField.placeholder = @"Mandatory";
              cell.textField.delegate = self;
              cell.textField.textColor = [UIColor blackColor];

          }
      }

      else if (indexPath.section == 3)
      {
          if(indexPath.row == 0)
          {
              cell.text = @"NOKIA";
              cell.textField.placeholder = @"Mandatory";
              cell.textField.delegate = self;
              cell.textField.textColor = [UIColor blackColor];
          }
          else if ( indexPath.row == 1)
          {
              cell.text = @"SAMSUNG";
              cell.textField.placeholder = @"Mandatory";
              cell.textField.delegate = self;
              cell.textField.textColor = [UIColor blackColor];
          }
          else
          {
              cell.text = @"SONY";
              cell.textField.placeholder = @"Mandatory";
             cell.textField.delegate = self;
              cell.textField.textColor = [UIColor blackColor];
          }
      }




  return cell;
}
时间：2011-02-16 05:33:59

From your initial code, the tableview is behaving normally.
You create cells for the first 3 sections because they are visible and there are no extra cell in the table view which you can reuse.
But, whenever you get scroll to the 4th section (which is not visible at first), you start reusing cells (which happen to be the ones from the 1st section that is not out of the screen).

为了不丢失用户在每个单元格中输入的数据，您需要将每个UITextField（或至少其中的文本）存储在一个单独的数组中。当表需要某个单元格时，可以在数组中查找文本字段。如果不存在，请创建并添加一个新的UITextField。

附言：我希望代码没有任何拼写错误。我在上班，这里没有mac。



@interface MainViewController : UITableViewController
 {
 NSMutableArray* textFields;
}
@end

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad 
{
  CGRect frameRect = CGRectMake(0,0,320,460);

  UITableView *tableView = [[UITableView alloc] initWithFrame:frameRect   
  style:UITableViewStyleGrouped];
  tableView.delegate = self;
  tableView.dataSource = self;  
  tableView.backgroundColor = [UIColor purpleColor];
  tableView.scrollEnabled = YES;

  self.view = tableView;
  [tableView release];

  [super viewDidLoad];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    // Return the number of rows in the section.
    return 3;
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    // Return the number of sections.
    return 4;
}

- (UITextField*)getTextFieldAtIndexPath:(NSIndexPath*)indexPath
{
    if (textFields == nil)
      textFields = [[NSMutableArray alloc] init];

    // Add padding, just in case UITableView doesn t need the cells in order
    while (indexPath.section >= [textFields count])
    {
        [textFields addObject:[NSNull null]];
    }

    // Get the section list
   NSMutableArray* sectionList = [textFields objectAtIndex:indexPath.section]; 

   if (sectionList == [NSNull null])
   {
     sectionList = [[[NSMutableArray alloc] init] autorelease];
     [textFields replaceObjectAtIndex:indexPath.section withObject:sectionList];
   }


   // Now that we have the section list, we need to do the same for the row
    while (indexPath.row >= [sectionList count])
    {
        [sectionList addObject:[NSNull null]];
    }

    UITextField* afield = [sectionList objectAtIndex:indexPath.row];

    if (afield == [NSNull null])
    {
      // If there was no afield stored there, just create a new one  
      afield = [[UITextField alloc] initWithFrame:CGRectMake(100,10,200,40)];
      afield.placeholder = @"Mandatory";
      afield.delegate = self;
      afield.textColor = [UIColor blackColor]; 

      [sectionList replaceObjectAtIndex:indexPath.row withObject:aField];

      [afield release];
    }

    return afield;
}

// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
{
     NSLog(@"CELL IS NIL %i", indexPath.section);

  static NSString *CellIdentifier = @"Cell";
  UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
  UITextField *aField;

 // If we can t reuse the cell, just create a new one
  if (cell == nil)
  {
      cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
  }
  else
  {
      // if we are reusing the cell, just remove the old textField to make room for the new one
      [[cell.contentView viewForTag:1234] removeFromSuperview];
  }

  // Get the text field for this cell. The method below will create a new one if it doesn t exist, or just return the existing one if found.
  aField = [self getTextFieldAtIndexPath:indexPath];

  // Just add this textfield to the cell
  [cell.contentView addSubView:aField];

  // Now that we added the textfield, we only need to set the title of the cell. The content of the textField will be cached and moved around.

      if (indexPath.section == 0)
      {
          if(indexPath.row == 0)
              cell.text = @"Tmail";
          else if ( indexPath.row == 1 )
              cell.text = @"English";
          else
              cell.text = @"Hindi";
      }
      else if (indexPath.section == 1)
      {
          if(indexPath.row == 0)
              cell.text = @"Street";
          else if ( indexPath.row == 1 )
              cell.text = @"City";
          else
              cell.text = @"State";
      }
      else if (indexPath.section == 2)
      {
          if(indexPath.row == 0)
              cell.text = @"Salem";
          else if ( indexPath.row == 1 )
              cell.text = @"Samalpatti";
          else
              cell.text = @"Chennai";
      }

      else if (indexPath.section == 3)
      {
          if(indexPath.row == 0)
              cell.text = @"NOKIA";
          else if ( indexPath.row == 1)
              cell.text = @"SAMSUNG";
          else
              cell.text = @"SONY";
      }
   }

  return cell;
}
时间：2011-02-16 11:22:22


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