Question

Im having problem in my UIscrollView,this is what I have done: Whenever a user picks an image (Multiple or Single) in camera roll thru a Imagepicker, I want to display it in my UIScrollView. I was able to display it, but when I go to the Imagepicker again then pick again an image,it doesnt update the UIScrollView, I tried putting my [self createScrollView] in my viewDidAppear but It recreates the UIScrollView but not update it, so the old images and new images are combined together. So I have put them in viewDidLoadbut It only update when I go to another View Controller then back again.

// My UIScrollView with thumbnail image

- (void) createScrollView {
    self.slotBg = [[UIView alloc] initWithFrame:CGRectMake(43, 370, 300, 143)];
    CAGradientLayer *gradient = [CAGradientLayer layer];
    gradient.frame = self.slotBg.bounds;
    gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor grayColor] CGColor], (id)[[UIColor whiteColor] CGColor], nil];
    [self.slotBg.layer insertSublayer:gradient atIndex:0];
    [self.view addSubview:self.slotBg];

    self.scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0.0f,0.0f,300.0f,134.0f)];
    [slotBg addSubview:self.scrollView];


    int row = 0;
    int column = 0;
    for(int i = 0; i < _thumbs.count; ++i) {

        UIImage *thumb = [_thumbs objectAtIndex:i];
        UIButton * button = [UIButton buttonWithType:UIButtonTypeCustom];
        button.frame = CGRectMake(column*60+10, row*60+10, 60, 60);
        [button setImage:thumb forState:UIControlStateNormal];
        [button addTarget:self 
                   action:@selector(buttonClicked:) 
         forControlEvents:UIControlEventTouchUpInside];
        button.tag = i; 

        [scrollView addSubview:button];

        if (column == 4) {
            column = 0;
            row++;
        } else {
            column++;
        }

    }

    [scrollView setContentSize:CGSizeMake(330, (row+1) * 60 + 10)];
}

// in my viewDidLoad

- (void)viewDidLoad
{
       for(int i = 0; i <= 100; i++) 
        { 
            NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
            NSString *documentsDir = [paths objectAtIndex:0];

            NSString *savedImagePath = [documentsDir stringByAppendingPathComponent:[NSString stringWithFormat:@"oneSlotImages%d.png", i]]; 
            NSLog(@"savedImagePath=%@",savedImagePath);
            if([[NSFileManager defaultManager] fileExistsAtPath:savedImagePath]){ 
                [self addImage:[UIImage imageWithContentsOfFile:savedImagePath]]; 

                NSLog(@"file exists");
            } 
        } 
        NSLog(@"Count : %d", [_images count]);
        [self createScrollView];
}

EDIT:

- (void) viewDidLoad {
    [self createScrollView];

    [_thumbs removeAllObjects];
    UIView *removeView;
    for(int i = 0; i < _thumbs.count; ++i) {
    while((removeView = [scrollView viewWithTag:i]) != nil) {
        [removeView removeFromSuperview];
    }

        { 
            NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
            NSString *documentsDir = [paths objectAtIndex:0];

            NSString *savedImagePath = [documentsDir stringByAppendingPathComponent:[NSString stringWithFormat:@"oneSlotImages%d.png", i]]; 
            NSLog(@"savedImagePath=%@",savedImagePath);
            if([[NSFileManager defaultManager] fileExistsAtPath:savedImagePath]){ 
                [self addImage:[UIImage imageWithContentsOfFile:savedImagePath]]; 
                NSLog(@"file exists");
            } 
        } 
        NSLog(@"Count : %d", [_images count]);
    }
}

Answer 1

There are two points:

1. Check for your data source. If image has been saved correctly in your documents directory or not.
2. No need to create scroll view and its parent view again. Move below code from createScrollView to viewDidLoad. these view should be created only once.

self.slotBg = [[UIView alloc] initWithFrame:CGRectMake(43, 370, 300, 143)];
CAGradientLayer *gradient = [CAGradientLayer layer];
gradient.frame = self.slotBg.bounds;
gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor grayColor] CGColor], (id)[[UIColor whiteColor] CGColor], nil];
[self.slotBg.layer insertSublayer:gradient atIndex:0];
[self.view addSubview:self.slotBg];

self.scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0.0f,0.0f,300.0f,134.0f)];
[slotBg addSubview:self.scrollView];

Now, from viewDidAppear, first update your _thumbs array (data source). Then call createScrollView function. Inside this function, first remove all the subviews using tag from UIScrollView. Add all the thumbs again as you have done. Then call [self setNeedsDisplay] before returning from createScrollView.