UICell problem iPhone while Scrolling tableView - iphone

Question

My Current Problem Related links are one of below.
http://www.freeimagehosting.net/image.php?a65dae5f4a.png>http://www.freeimagehosting.net/uploads/th.a65dae5f4a.png alt="Free Image Hosting by FreeImageHosting.net">
[url=http://www.freeimagehosting.net/image.php?a65dae5f4a.png][img]http://www.freeimagehosting.net/uploads/th.a65dae5f4a.png[/img][/url]
[url=http://www.freeimagehosting.net/image.php?a65dae5f4a.png][img=http://www.freeimagehosting.net/uploads/th.a65dae5f4a.png][/url]
http://www.freeimagehosting.net/>http://www.freeimagehosting.net/uploads/a65dae5f4a.png border=0 alt="Free Image Hosting">
[url=http://www.freeimagehosting.net/][img]http://www.freeimagehosting.net/uploads/a65dae5f4a.png[/img][/url]
[url=http://www.freeimagehosting.net/][img=http://www.freeimagehosting.net/uploads/a65dae5f4a.png][/url]
I have implemented following code, to my Table view,
enter code here
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
}
// customizing cell
student *t=[studentsList objectAtIndex:indexPath.row];
cell.backgroundColor=[UIColor lightGrayColor];
CGRect label1Frame=CGRectMake(10, 10, 290, 25);
CGRect label2Frame=CGRectMake(10, 33, 290, 25);
CGRect label3Frame=CGRectMake(10, 56, 290, 25);
UILabel *lbltmp;
lbltmp=[[UILabel alloc] initWithFrame:label1Frame]; // name
lbltmp.font=[UIFont boldSystemFontOfSize:15];
lbltmp.backgroundColor=[UIColor clearColor];
lbltmp.textColor=[UIColor blackColor];
lbltmp.text=t.stuName;
[cell.contentView addSubview:lbltmp];
[lbltmp release];
lbltmp=[[UILabel alloc] initWithFrame:label2Frame]; // roll no & address
lbltmp.font=[UIFont systemFontOfSize:13];
lbltmp.backgroundColor=[UIColor clearColor];
lbltmp.text=[NSString stringWithFormat:#"%i - %#",t.stuNo,t.stuAddress];
lbltmp.textColor=[UIColor grayColor];
[cell.contentView addSubview:lbltmp];
[lbltmp release];
lbltmp=[[UILabel alloc] initWithFrame:label3Frame]; // city & pin
lbltmp.font=[UIFont systemFontOfSize:13];
lbltmp.backgroundColor=[UIColor clearColor];
lbltmp.text=[NSString stringWithFormat:#"%# - %#",t.stuCity,t.stuPin];
lbltmp.textColor=[UIColor grayColor];
[cell.contentView addSubview:lbltmp];
[lbltmp release];
//----------------------------------
cell.accessoryType=UITableViewCellAccessoryDetailDisclosureButton;
return cell;
}
If I implement the code as described above, problem occurs as described in above images.
If I implement following code, no problem occurs.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
// customizing cell
student *t=[studentsList objectAtIndex:indexPath.row];
cell.backgroundColor=[UIColor lightGrayColor];
CGRect label1Frame=CGRectMake(10, 10, 290, 25);
CGRect label2Frame=CGRectMake(10, 33, 290, 25);
CGRect label3Frame=CGRectMake(10, 56, 290, 25);
UILabel *lbltmp;
lbltmp=[[UILabel alloc] initWithFrame:label1Frame]; // name
lbltmp.font=[UIFont boldSystemFontOfSize:15];
lbltmp.backgroundColor=[UIColor clearColor];
lbltmp.textColor=[UIColor blackColor];
lbltmp.text=t.stuName;
[cell.contentView addSubview:lbltmp];
[lbltmp release];
lbltmp=[[UILabel alloc] initWithFrame:label2Frame]; // roll no & address
lbltmp.font=[UIFont systemFontOfSize:13];
lbltmp.backgroundColor=[UIColor clearColor];
lbltmp.text=[NSString stringWithFormat:#"%i - %#",t.stuNo,t.stuAddress];
lbltmp.textColor=[UIColor grayColor];
[cell.contentView addSubview:lbltmp];
[lbltmp release];
lbltmp=[[UILabel alloc] initWithFrame:label3Frame]; // city & pin
lbltmp.font=[UIFont systemFontOfSize:13];
lbltmp.backgroundColor=[UIColor clearColor];
lbltmp.text=[NSString stringWithFormat:#"%# - %#",t.stuCity,t.stuPin];
lbltmp.textColor=[UIColor grayColor];
[cell.contentView addSubview:lbltmp];
[lbltmp release];
//----------------------------------
cell.accessoryType=UITableViewCellAccessoryDetailDisclosureButton;
}
return cell;
}
Implementing the above code means, recreating the each table cell while user scrolls the tableView. It may slow down your application & it isn't the correct solution,
Because In my application I have thousands of students & if I create each cell while scroll My Application may hang. What Should be the solution? Help me....

Answer 1

I think the problem is that you're adding subviews on top of already-added subviews when the cells are recycled.
One way to fix this: subclass UITableViewCell and give it pointers to UILabels for the text you want to change. Then when the cell is recycled, you can just access those properties, instead of re-adding new subviews.
Reference: An Apple doc on table view cells.

Answer 2

I think the solution to your problem is as follows:
Implement following method to your tableViewCotroller
-(UITableViewCell*)getCellContentView:(NSString*)cellIdentifier
{
}
For example I have Implemented following
-(UITableViewCell*)getCellContentView:(NSString*)cellIdentifier
{
CGRect photoFrame=CGRectMake(5, 5, 60, 60);
CGRect label1Frame=CGRectMake(90, 10, 290, 25);
CGRect label2Frame=CGRectMake(90, 30, 290, 25);
CGRect label3Frame=CGRectMake(90, 50, 290, 25);
UITableViewCell *cell=[[[UITableViewCell alloc] initWithFrame:CGRectMake(0, 0, 300, 80) reuseIdentifier:cellIdentifier] autorelease];
UILabel *tmp;
tmp=[[UILabel alloc] initWithFrame:label1Frame];
tmp.tag=1;
tmp.textColor=[UIColor blackColor];
tmp.font=[UIFont boldSystemFontOfSize:15];
[cell.contentView addSubview:tmp];
[tmp release];
tmp=[[UILabel alloc] initWithFrame:label2Frame];
tmp.tag=2;
tmp.adjustsFontSizeToFitWidth=0;
tmp.textColor=[UIColor grayColor];
tmp.font=[UIFont systemFontOfSize:13];
[cell.contentView addSubview:tmp];
[tmp release];
tmp=[[UILabel alloc] initWithFrame:label3Frame];
tmp.tag=3;
tmp.adjustsFontSizeToFitWidth=0;
tmp.textColor=[UIColor grayColor];
tmp.font=[UIFont systemFontOfSize:13];
[cell.contentView addSubview:tmp];
[tmp release];
UIImageView *imgView=[[UIImageView alloc]initWithFrame:photoFrame];
imgView.tag=4;
[cell.contentView addSubview:imgView];
[imgView release];
return cell;
}
I have also called above method form cellForRowAtIndexPath
example
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [self getCellContentView:CellIdentifier];
}
// customizing cell
student *t=[studentsList objectAtIndex:indexPath.row];
cell.backgroundColor=[UIColor lightGrayColor];
UILabel *lb1=(UILabel*)[cell viewWithTag:1];
UILabel *lb2=(UILabel*)[cell viewWithTag:2];
UILabel *lb3=(UILabel*)[cell viewWithTag:3];
NSString *dtlOne=[NSString stringWithFormat:#"Enr.No - %i, %#",t.stuNo,t.stuAddress];
NSString *dtlTwo=[NSString stringWithFormat:#"%# - %#.",t.stuCity,t.stuPin];
lb1.text=t.stuName;
lb2.text=dtlOne;
lb3.text=dtlTwo;
cell.accessoryType=UITableViewCellAccessoryDetailDisclosureButton;
return cell;
}
That works perfectly, and I can also use my custom content view in my cell.