Memory Warning when cells are recreated in tableView - ios

Question

I am displaying 100 remote images in tableview
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
//static NSString *CellIdentifier = #"Cell";
NSString *CellIdentifier = [NSString stringWithFormat:#"%d",indexPath.row];
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
}
cell.imageView.image = nil;
cell.textLabel.text = nil;
cell.detailTextLabel.text = nil;
cell.selectionStyle = UITableViewCellSelectionStyleNone;
// Configure the cell...
for (UIView *view in cell.contentView.subviews) {
if ([view isKindOfClass:[UIButton class]] || [view isKindOfClass:[UILabel class]]||[view isKindOfClass:[UIImageView class]]) {
[view removeFromSuperview];
}
}
int imageNumber = 0;
if (isInSearchMode)
{
PhotoVO *photoVO = (PhotoVO *)[searchResultArray objectAtIndex:indexPath.row];
UIImageView *photo_View = [[UIImageView alloc]initWithFrame:CGRectMake(20, 5, width , height - 10)];
photo_View.tag = 101;
[[photo_View layer] setBorderWidth:3.0f];
[[photo_View layer] setBorderColor:[UIColor whiteColor].CGColor];
[photo_View setImageWithURL:[NSURL URLWithString:photoVO.thumb_URL1] placeholderImage:[UIImage imageNamed:#"loader"]];
[cell.contentView addSubview:photo_View];
UILabel *stringLable=[[UILabel alloc]initWithFrame:CGRectMake(130, 20, 150, 30)];
stringLable.backgroundColor=[UIColor clearColor];
stringLable.text=photoVO.photoName;
stringLable.font=[UIFont systemFontOfSize:16.0];
[cell.contentView addSubview:stringLable];
UILabel *tagLable=[[UILabel alloc]initWithFrame:CGRectMake(130, 55, 150, 30)];
tagLable.backgroundColor=[UIColor clearColor];
tagLable.text=photoVO.tagString;
tagLable.font=[UIFont systemFontOfSize:12.0];
[cell.contentView addSubview:tagLable];
}
else
{
for (int i = (indexPath.row * imagesCount); i < ((indexPath.row *imagesCount) + imagesCount); i++) {
if (i < [cellImageVOArray count]) { // If resultsArray Count is odd then we no need to create cell image
PhotoVO *photoVo = (PhotoVO *)[cellImageVOArray objectAtIndex:i];
UIButton *appIconBtn = [UIButton buttonWithType:UIButtonTypeCustom];
appIconBtn.frame = CGRectMake(((imageNumber * 5)+5)+(imageNumber * width), 2, width, height -4);
appIconBtn.tag = i + 100;
[[appIconBtn layer] setBorderWidth:3.0f];
[[appIconBtn layer] setBorderColor:[UIColor whiteColor].CGColor];
[appIconBtn addTarget:self action:#selector(imageTapped:) forControlEvents:UIControlEventTouchUpInside];
[appIconBtn setBackgroundImageWithURL:[NSURL URLWithString:photoVo.thumb_URL1] placeholderImage:[UIImage imageNamed:#"loader.png"]];
//[appIconBtn setBackgroundImageWithURL:[NSURL URLWithString:photoVo.thumb_URL1]];
[cell.contentView addSubview:appIconBtn];
imageNumber ++;
}
}
}
return cell;
}
I am using the above code for displaying the images in tableView, but I get a memory warning in all ways I check it. I think the cell is created every time so please tell me if you see any problem in the code.

Answer 1

This is a problem: NSString *CellIdentifier = [NSString stringWithFormat:#"%d",indexPath.row];
You aren't reusing anything because you're creating a new identifier for each cell. Its fine to have a couple different cell styles reusable, but you're just creating a new cell for every single row.
Second, You need to think about what you're doing here:
for (UIView *view in cell.contentView.subviews) {
if ([view isKindOfClass:[UIButton class]] || [view isKindOfClass:[UILabel class]]||[view isKindOfClass:[UIImageView class]]) {
[view removeFromSuperview];
}
}
Everytime a cell is needed you're removing the parts that make the cell, then remaking them right after. You should be reusing as much as possible in a UITableView. You should look into creating a custom subclass of UITableViewCell that has the pieces you need, then use that. That being said it looks like you just have an image and two labels which a default UITableViewCell would have so you can probably not have to create them at all unless your cell is extremely custom.
Finally, you should look at what you're doing with isInSearchMode. Right now you basically have an if statement for the entire table. Thats not a horrible thing but if you do that you should have two cell identifiers, one for each possible cell. Then in the if statement just swap cell identifiers and fill in the appropriate data.
Above all, if at all possible (which it seems to be in your case) you should not be creating new views in this method at all. You should let the UITableViewCell handle that.
Creating Custom Cells
You start with a simple subclass of UITableViewCell. Then you can add a property for each custom part you need like a UILabel or UIImageView. And you can either create those by overriding init, or you could put them in a custom property getter that creates them on demand.
// CustomCell.h
#import <UIKit/UIKit.h>
#interface Custom : UITableViewCell
#property (strong, nonatomic) UILabel *titleLabel;
#end
// CustomCell.m
#import "CustomCell.h"
#implementation CustomCell
- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier
{
self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
if (self) {
self.titleLabel = [[UILabel alloc] initWithFrame:CGRectMake(12.0, 10.0, self.contentView.frame.size.width - 24.0, 22.0)];
[self.titleLabel setAutoresizingMask:UIViewAutoresizingFlexibleWidth];
[self.titleLabel setHighlightedTextColor:[UIColor whiteColor]];
[self.titleLabel setFont:[UIFont boldSystemFontOfSize:17.0]];
[self.titleLabel setBackgroundColor:[UIColor clearColor]];
[self.titleLabel setTextColor:[UIColor blackColor]];
[self.titleLabel setAdjustsFontSizeToFitWidth:YES];
[self.titleLabel setMinimumFontSize:8.0];
[self.contentView addSubview:self.titleLabel];
}
return self;
}
#end
Then you just need to rewrite your cellForRowAtIndexPath: to use your custom class. And in your case you could have two custom cells and switch between them. This will create only enough of each cell on demand and reuse them as they move on and off screen.
static NSString *CellIdentifier = #"Cell";
static NSString *SearchCellIdentifier = #"SearchCell";
if (isInSearchMode) {
SearchCell *cell = (SearchCell *)[tableView dequeueReusableCellWithIdentifier:SearchCellIdentifier];
if (cell == nil) {
cell = [[SearchCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
}
cell.titleLabel = #"Custom Search Title";
} else {
CustomCell *cell = (CustomCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[CustomCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
}
cell.titleLabel = #"Custom Title";
}
This could easily be refactored even further depending on how your application works but this should get you on the right path.

Answer 2

Yes, you have different cell identifiers for every row, so there is no reusing happening.
Change:
NSString *CellIdentifier = [NSString stringWithFormat:#"%d",indexPath.row];
to
NSString *CellIdentifier = #"CellId";