UITableView with performance issues - iphone

Question

I make an UITableview (with IB) in my application with 3 types of cell. All works fine except when i drag my tableview all become very slow. So if someone can help me to improve the performance of my app it'll be cool.
My Code for the tableview :
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return [[myData objectForKey:#"listnews"] count];
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
if (indexPath.row == 0) {
return 154;
}
if (indexPath.row == 1) {
return 34;
}
else return 70;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
[myTextField resignFirstResponder];
ListNewsCell *cCell = (ListNewsCell *)[myTable dequeueReusableCellWithIdentifier:[NSString stringWithFormat:#"cCellIdentifier%d",indexPath.row]];
cCell = [[ListNewsCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:[NSString stringWithFormat:#"cCellIdentifier%d",indexPath.row]];
if (indexPath.row == 0) {
NSString * caroline = [[[myData objectForKey:#"listnews"] objectAtIndex:indexPath.row] objectForKey:#"urlimage"];
cCell.c1Image1.image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#",caroline]]]];
cCell.c1Image2.image = [UIImage imageNamed:#"barreNoireHub.png"];
NSString * sophie = [[[myData objectForKey:#"listnews"] objectAtIndex:indexPath.row] objectForKey:#"titre"];
NSString *itemTitle = sophie ? [sophie stringByConvertingHTMLToPlainText] : #"[No Title]";
cCell.c1Label1.text = itemTitle;
NSString * sonia = [[[myData objectForKey:#"listnews"] objectAtIndex:indexPath.row] objectForKey:#"extrait"];
NSString *itemExtrait = sonia ? [sonia stringByConvertingHTMLToPlainText] : #"[No Title]";
cCell.c1Label2.text = itemExtrait;
}
if (indexPath.row == 1) {
UIImageView * imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 34)];
imageView.backgroundColor = [UIColor whiteColor];
imageView.image = [UIImage imageNamed:#"barreSearchHub.png"];
[cCell addSubview:imageView];
[imageView release];
UIView * insertView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 34)];
myTextField = [[UITextField alloc] initWithFrame:CGRectMake(15, 6, 270, 25)];
myTextField.placeholder = #"Recherche";
myTextField.tag = 1;
myTextField.delegate = self;
myTextField.returnKeyType = UIReturnKeySearch;
[insertView addSubview:myTextField];
cCell.accessoryView = insertView;
}
if (indexPath.row > 1) {
cCell.c2Image1.image = [UIImage imageNamed:#"cellM.png"];
NSString * caroline = [[[myData objectForKey:#"listnews"] objectAtIndex:indexPath.row] objectForKey:#"urlimage"];
cCell.c2Image2.image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#",caroline]]]];
NSString * sophie = [[[myData objectForKey:#"listnews"] objectAtIndex:indexPath.row] objectForKey:#"titre"];
NSString *itemTitle = sophie ? [sophie stringByConvertingHTMLToPlainText] : #"[No Title]";
cCell.c2Label1.text = itemTitle;
NSString * sonia = [[[myData objectForKey:#"listnews"] objectAtIndex:indexPath.row] objectForKey:#"extrait"];
NSString *itemExtrait = sonia ? [sonia stringByConvertingHTMLToPlainText] : #"[No Title]";
cCell.c2Label2.text = itemExtrait;
}
return cCell;
}
The code of the UITableViewCell:
#import "ListNewsCell.h"
#implementation ListNewsCell
#synthesize c1Image1, c1Image2, c1Label1, c1Label2;
#synthesize c2Image1, c2Image2, c2Label1, c2Label2;
- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier
{
self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
if (self) {
c1Image1 = [[UIImageView alloc] initWithFrame:CGRectMake(0,0,320,154)];
c1Image1.backgroundColor = [UIColor clearColor];
[self addSubview:c1Image1];
[c1Image1 release];
c1Image2 = [[UIImageView alloc] initWithFrame:CGRectMake(0,98,320,56)];
c1Image2.backgroundColor = [UIColor clearColor];
[self addSubview:c1Image2];
[c1Image2 release];
c1Label1 = [[UILabel alloc] initWithFrame:CGRectMake(5, 100, 310, 20)];
c1Label1.font = [UIFont fontWithName:#"Arial-BoldMT" size:14];
c1Label1.textColor = [UIColor whiteColor];
c1Label1.backgroundColor = [UIColor clearColor];
[self addSubview:c1Label1];
c1Label2 = [[UILabel alloc] initWithFrame:CGRectMake(5, 112, 310, 45)];
c1Label2.font = [UIFont fontWithName:#"Arial" size:12];
c1Label2.textColor = [UIColor whiteColor];
c1Label2.numberOfLines = 2;
c1Label2.backgroundColor = [UIColor clearColor];
[self addSubview:c1Label2];
c2Image1 = [[UIImageView alloc] initWithFrame:CGRectMake(0,0,320,70)];
c2Image1.backgroundColor = [UIColor clearColor];
[self addSubview:c2Image1];
[c2Image1 release];
c2Label1 = [[UILabel alloc] initWithFrame:CGRectMake(105, 8, 180, 20)];
c2Label1.font = [UIFont fontWithName:#"Arial-BoldMT" size:14];
c2Label1.textColor = [UIColor blackColor];
c2Label1.backgroundColor = [UIColor clearColor];
[self addSubview:c2Label1];
c2Label2 = [[UILabel alloc] initWithFrame:CGRectMake(105, 25, 180, 45)];
c2Label2.font = [UIFont fontWithName:#"Arial" size:12];
c2Label2.textColor = [UIColor blackColor];
c2Label2.numberOfLines = 2;
c2Label2.backgroundColor = [UIColor clearColor];
[self addSubview:c2Label2];
c2Image2 = [[UIImageView alloc] initWithFrame:CGRectMake(20,10,75,55)];
c2Image2.backgroundColor = [UIColor clearColor];
[self addSubview:c2Image2];
[c2Image2 release];
}
return self;
}
- (void)setSelected:(BOOL)selected animated:(BOOL)animated
{
[super setSelected:selected animated:animated];
}
- (void)dealloc
{
[super dealloc];
}
#end
Thanks to all !

Answer 1

The following line causes the big delay:
cCell.c2Image2.image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#",caroline]]]];
Everytime one of these cells will be loaded, it will make a URL Request. Try to preload a bunch of the data instead of requesting it per cell.
Load the image once, make it a class variable, then just reuse its pointer like:
cCell.c2Image2.image = preloadedImage;
Declare in your .h file:
UIImage * preloadedImage;
And in the - (void) loadView -method put:
preloadedImage = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#",caroline]]]];
Also mind that as jrturton wrote, you want to reuse your dequeued cells for the extra performance boost.

Answer 2

You are never reusing your dequeued cells, so you are recreating everything from scratch every time. Since you have a unique cell for each row (is this really necessary for cells in row 2 and above?) you only need to create and populate them once.
So, you could wrap everything after dequeueReusableCellWithIdentifier onwards inside if (cCell == nil) (the return statement excepted, obviously).

Answer 3

In cellForRowAtIndexPath method you have dequeued some cells from the table view. But you have never used that value. That caused the problem of loading every time rather than re-using.
Try the following code in which I've modified a little..
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
[myTextField resignFirstResponder];
ListNewsCell *cCell = (ListNewsCell *)[myTable dequeueReusableCellWithIdentifier:[NSString stringWithFormat:#"cCellIdentifier%d",indexPath.row]];
if(cCell == nil)
{
cCell = [[ListNewsCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:[NSString stringWithFormat:#"cCellIdentifier%d",indexPath.row]];
}
if (indexPath.row == 0) {
// Some code here
}
if (indexPath.row == 1) {
//Some code here
}
if (indexPath.row > 1) {
// some code here
}
return cCell;
}
Thanks,
Arun.