UIScrollView adding UIImageViews

Question

I want to add n number of views to a scroll view with paging enabled.

if hit the "add view" button say 5 times, all 5 get added w/out uiimageviews. but if I swipe to the 2nd view and click "add view" again, 2 UIImageViews get added to the scroll view (subviews). why are these image views being added after I swipe to the next view?

here I set up the view:

- (void)viewDidLoad
{    
    CGRect myRect = CGRectMake(0, 150, ([[UIScreen mainScreen] bounds].size.width), ([[UIScreen mainScreen] bounds].size.height - (64 + 150)));

    UIScrollView *myScrollView = [[UIScrollView alloc] initWithFrame:myRect];
    myScrollView.backgroundColor = [UIColor lightGrayColor];
    myScrollView.pagingEnabled = TRUE;
    myScrollView.showsHorizontalScrollIndicator = TRUE;

    myRect = CGRectMake(20, 75, 150, 13);

    myRect = CGRectMake(400, 50, 100, 50);

    UIButton *myButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    myButton.frame = CGRectMake(400, 50, 100, 50);
    myButton.titleLabel.text = @"get views";
    [myButton addTarget:self action:@selector(makePlantEvent:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:myButton];

    myRect = CGRectMake(0, 0, (768/2), (1004/2));

    [self.view addSubview:myScrollView];

    self.mainScrollView = myScrollView;

    [super viewDidLoad];
}

and here is my method for adding views:

-(IBAction)makePlantEvent:(id)sender
{    
    NSLog(@"number of views in scrollview: %d", [self.mainScrollView.subviews count]);
    NSLog(@"views in scrollView: %@", self.mainScrollView.subviews);

    if ([self.mainScrollView.subviews count] == 0)
    {
        NSLog(@"adding first view");
        CGRect myRect = CGRectMake(10, 10, self.mainScrollView.frame.size.width - 20, self.mainScrollView.frame.size.height - 20);

        UIView *myUIView = [[UIView alloc] initWithFrame:myRect];
        myUIView.backgroundColor = [UIColor whiteColor];
        myUIView.layer.borderWidth = 1.0f;
        myUIView.layer.borderColor = [UIColor blackColor].CGColor;

        self.mainScrollView.contentSize = CGSizeMake(768, mainScrollView.frame.size.height);

        [self.mainScrollView addSubview:myUIView];
    }

    else if ([self.mainScrollView.subviews count] >= 1)
    {
    NSLog(@"adding %d view", ([self.mainScrollView.subviews count] + 1));

        self.mainScrollView.contentSize = CGSizeMake((768 * ([self.mainScrollView.subviews count] + 1)), mainScrollView.frame.size.height);

        CGRect myRect = CGRectMake((768 * [self.mainScrollView.subviews count]) + 10, 10, self.mainScrollView.frame.size.width - 20, self.mainScrollView.frame.size.height - 20);

        UIView *myUIView = [[UIView alloc] initWithFrame:myRect];
        myUIView.backgroundColor = [UIColor blueColor];
        myUIView.layer.borderWidth = 1.0f;
        myUIView.layer.borderColor = [UIColor blackColor].CGColor;

        [self.mainScrollView addSubview:myUIView];
    }

    NSLog(@"at end number of views in scrollview: %d", [self.mainScrollView.subviews count]);
    NSLog(@"at end views in scrollView: %@", self.mainScrollView.subviews);
}

my output: add 2 views

2011-11-28 13:42:39.976 Inspect[87637:207] BEGINING OF METHOD number of views in scrollview: 0
2011-11-28 13:42:39.977 Inspect[87637:207] BEGINING OF METHODviews in scrollView: (
)
2011-11-28 13:42:39.978 Inspect[87637:207] adding first view
2011-11-28 13:42:39.978 Inspect[87637:207] at end number of views in scrollview: 1
2011-11-28 13:42:39.979 Inspect[87637:207] at end views in scrollView: (
    "<UIView: 0x8874140; frame = (10 10; 748 790); layer = <CALayer: 0x8877d60>>"
)
2011-11-28 13:42:41.652 Inspect[87637:207] BEGINING OF METHOD number of views in scrollview: 1
2011-11-28 13:42:41.653 Inspect[87637:207] BEGINING OF METHODviews in scrollView: (
    "<UIView: 0x8874140; frame = (10 10; 748 790); layer = <CALayer: 0x8877d60>>"
)
2011-11-28 13:42:41.654 Inspect[87637:207] adding 2 view
2011-11-28 13:42:41.654 Inspect[87637:207] at end number of views in scrollview: 2
2011-11-28 13:42:41.655 Inspect[87637:207] at end views in scrollView: (
    "<UIView: 0x8874140; frame = (10 10; 748 790); layer = <CALayer: 0x8877d60>>",
    "<UIView: 0x8a1f390; frame = (778 10; 748 790); layer = <CALayer: 0x8a26d70>>"
)

swipe to 2nd view and click button again:

2011-11-28 13:42:49.628 Inspect[87637:207] BEGINING OF METHOD number of views in scrollview: 4
2011-11-28 13:42:49.629 Inspect[87637:207] BEGINING OF METHODviews in scrollView: (
    "<UIView: 0x8874140; frame = (10 10; 748 790); layer = <CALayer: 0x8877d60>>",
    "<UIView: 0x8a1f390; frame = (778 10; 748 790); layer = <CALayer: 0x8a26d70>>",
    "<UIImageView: 0x108016d0; frame = (760 1; 7 808); alpha = 0; opaque = NO; autoresize = LM; userInteractionEnabled = NO; layer = <CALayer: 0x10800200>>",
    "<UIImageView: 0x10801690; frame = (1152 802; 383 7); alpha = 0; opaque = NO; autoresize = TM; userInteractionEnabled = NO; layer = <CALayer: 0x108000a0>>"
)
2011-11-28 13:42:49.630 Inspect[87637:207] adding 3 view
2011-11-28 13:42:49.630 Inspect[87637:207] at end number of views in scrollview: 5
2011-11-28 13:42:49.631 Inspect[87637:207] at end views in scrollView: (
    "<UIView: 0x8874140; frame = (10 10; 748 790); layer = <CALayer: 0x8877d60>>",
    "<UIView: 0x8a1f390; frame = (778 10; 748 790); layer = <CALayer: 0x8a26d70>>",
    "<UIImageView: 0x108016d0; frame = (760 1; 7 808); alpha = 0; opaque = NO; autoresize = LM; userInteractionEnabled = NO; layer = <CALayer: 0x10800200>>",
    "<UIImageView: 0x10801690; frame = (1152 802; 383 7); alpha = 0; opaque = NO; autoresize = TM; userInteractionEnabled = NO; layer = <CALayer: 0x108000a0>>",
    "<UIView: 0xf4002f0; frame = (3082 10; 748 790); layer = <CALayer: 0xf4001c0>>"

so the swipe adds the two UIImageViews. Why?

Answer 1

There are scroll indicators. When your scrollview contentSize > scrollview size then UIScrollView automatically adds two subviews (UIImageView) to itself.

To disable this feature set showsHorizontalScrollIndicator and showsVerticalScrollIndicator properties to NO.