将UIButtons添加为子视图时，UIScrollView不滚动

Question

I'm trying to build a simple UIScrollView with paging to horizontally scroll between 3 images. The tricky part is that I would like that each image would be clickable and catch the click event.

My technique is to create 3 UIButtons that each consists UIImage. give each button a tag and set an action.

Problem: I can catch the click event - BUT it's not scrollable!

Here is my code:

- (void) viewDidAppear:(BOOL)animated {

    _imageArray = [[NSArray alloc] initWithObjects:@"content_01.png", @"content_02.png", @"content_03.png", nil];

    for (int i = 0; i < [_imageArray count]; i++) {
        //We'll create an imageView object in every 'page' of our scrollView.
        CGRect frame;
        frame.origin.x = _contentScrollView.frame.size.width * i;
        frame.origin.y = 0;
        frame.size = _contentScrollView.frame.size;

        //
        //get the image to use, however you want
        UIImage* image = [UIImage imageNamed:[_imageArray objectAtIndex:i]];

        UIButton* button = [[UIButton alloc] initWithFrame:frame];

        //set the button states you want the image to show up for
        [button setImage:image forState:UIControlStateNormal];
        [button setImage:image forState:UIControlStateHighlighted];

        //create the touch event target, i am calling the 'productImagePressed' method
        [button addTarget:self action:@selector(imagePressed:)
         forControlEvents:UIControlEventTouchUpInside];
        //i set the tag to the image #, i was looking though an array of them
        button.tag = i;

        [_contentScrollView addSubview:button];
    }

    //Set the content size of our scrollview according to the total width of our imageView objects.
    _contentScrollView.contentSize = CGSizeMake(_contentScrollView.frame.size.width * [_imageArray count], _contentScrollView.frame.size.height);

    _contentScrollView.backgroundColor = [ENGAppDelegate backgroundColor];
    _contentScrollView.delegate = self;
}

Answer 1

Well, since UIButton is an UIControl subclass, it "eats up" the touches of your scroll view:

[UIScrollView touchesShouldCancelInContentView:] The default returned value is YES if view is not a UIControl object; otherwise, it returns NO.

(from https://developer.apple.com/library/ios/documentation/uikit/reference/UIScrollView_Class/Reference/UIScrollView.html#//apple_ref/occ/instm/UIScrollView/touchesShouldCancelInContentView :)

You could influence this by subclassing UIScrollView and overwriting touchesShouldCancelInContentView: (and/or touchesShouldBegin:withEvent:inContentView: ). However, for your use case I'd not use buttons in the first place. Why not just add a tap gesture recognizer to the scrollview and use the touch point to determine which image has been tapped? That's much easier and should work without any issues.