Question

When i checked a cell, the image associated is changed, but when i had scrolled down and up, the cell got its default image this is my code:

- (UITableViewCell *)tableView:(UITableView *)tableView

         cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    static NSString *SimpleTableIdentifier = @"SimpleTableIdentifier";
    NSArray *listData =[self->tableContents objectForKey:
                        [self->sortedKeys objectAtIndex:[indexPath section]]];
    UITableViewCell * cell = [tableView dequeueReusableCellWithIdentifier: SimpleTableIdentifier];
    if(cell == nil) {
        cell = [[UITableViewCell alloc]
                initWithStyle:UITableViewCellStyleDefault
                reuseIdentifier:SimpleTableIdentifier];
    }
    NSUInteger row = [indexPath row];
    cell.textLabel.text = [listData objectAtIndex:row];
    UIImageView *unchecked = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"unchecked.png"]];
UIImageView *checked = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"checked.png"]];

BOOL bChecked = NO;//By default, it's unchecked, so NO

/// Assign cell according to `bChecked`
cell.accessoryView = (bChecked ? checked : unchecked); 
return cell;

}

EDIT:

I have edited my code to look as above, but i still get the issue, the default image is getting back when i scroll up my table view.

EDIT 2:
@Openside: So according to your approach, my snippet should look like this:

- (UITableViewCell *)tableView:(UITableView *)tableView

         cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    static NSString *SimpleTableIdentifier = @"SimpleTableIdentifier";
    NSArray *listData =[self->tableContents objectForKey:
                        [self->sortedKeys objectAtIndex:[indexPath section]]];

    UITableViewCell * cell = [tableView dequeueReusableCellWithIdentifier: SimpleTableIdentifier];
    if(cell == nil) {
        cell = [[UITableViewCell alloc]
                initWithStyle:UITableViewCellStyleDefault
                reuseIdentifier:SimpleTableIdentifier];
    }
    NSUInteger row = [indexPath row];
    textClass *myText = (textClass*)[listData objectAtIndex:row];
    cell.textLabel.text = myText.text;
    UIImageView *unchecked = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"unchecked.png"]];
    UIImageView *checked = [[UIImageView alloc] initWithImage:[UIImage  imageNamed:@"checked.png"]];



    cell.accessoryView = (myText.isChecked ? checked : unchecked); 
    return cell;
}


- (void)tableView:(UITableView *)tableView

didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

    textClass *myText=[[textClass alloc]init];
    myText.isChecked=YES;
}

I got this exception:

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFConstantString text]: unrecognized selector sent to instance 0x673bc'

The line indicating the exception issue is this (in cellForRowAtIndexPath delegate method):

cell.textLabel.text = myText.text;

I have added the class textClass although i am not so convinced, i think i can use a property in the holder class of my UITableView.

Answer 1

The problem is that the cell will be refreshed (or reused hence the dequeueReusableCellWithIdentifier ) when you scroll it out of view and then back into view. You need to have a flag on your source object to say if it’s checked or not and then add an if statement to determine if the checked.png or unchecked.png image is used.

However, looking at your code the source object is just text, it may be worth creating a subclassed NSObject with two properties

text and
checked

Then your cellForRowAtIndexPath code can determine which image to show.

I hope that helps.

- (UITableViewCell *)tableView:(UITableView *)tableView

     cellForRowAtIndexPath:(NSIndexPath *)indexPath {

static NSString *SimpleTableIdentifier = @"SimpleTableIdentifier";
UITableViewCell * cell = [tableView dequeueReusableCellWithIdentifier: SimpleTableIdentifier];
if(cell == nil) {
    cell = [[UITableViewCell alloc]
            initWithStyle:UITableViewCellStyleDefault
            reuseIdentifier:SimpleTableIdentifier];
}
NSUInteger row = [indexPath row];
textClass *myText = (textClass*)[listData objectAtIndex:row];
cell.textLabel.text = myText.text;
UIImageView *unchecked = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"unchecked.png"]];
UIImageView *checked = [[UIImageView alloc] initWithImage:[UIImage  imageNamed:@"checked.png"]];



/// Assign cell according to `bChecked`
cell.accessoryView = (myText.isChecked ? checked : unchecked); 
return cell;

}

@interface textClass : NSObject {

@private
    NSString *_text;
    BOOL _isChecked;
}

@property (nonatomic, retain) NSString *text;
@property (nonatomic, assign) BOOL isChecked;

@end

@implementation textClass

@synthesize text = _text;
@synthesize isChecked = _isChecked;

@end

Ok so here I have created a class called textClass it has two properties text and isChecked. When you load your view populate an NSMutableArray (listData) with these objects using the text you were previously using. When your cell gets checked set the isChecked property to YES when the cell gets reused this property has retained its state outside of the delegate method and should render correctly.