how does a subview of a scrollview know the scrollview is being scrolled

开发者_开发知识库I placed a few uiimageview objects into a scrollview. How can the imageview know the scrollview is being scrolled? Since the imageview is a subview of the scrollview i can't set the scrollview delegate to the imageview.

I want to create something similar to the apps view on the iphone. Where you can hold down an app and then drag it, but if you hold and move your finger too far to the left or right the action is stopped and scrolling takes over.

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"Since the imageview is a subview of the scrollview i can't set the scrollview delegate to the imageview."

And why not?

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You have viewcontroller which shows the particular scrollview correct? this viewcontroller should be the delegate of the scrollview, and viewcontroller should also hold pointers (either explicitly in an array or through tag of some sort) to the uiimageviews.

Then, whenever scrollview notifies viewcontroller (through scrollviewdidscroll type of delegate method), implement your logic to update uiimageview.

To implement the exact touch sequence, you can subclass UIGestureRecognizer or write your own touch handler.. take a look at Apple's documentation on Event Handling Guide :

http://developer.apple.com/library/ios/#documentation/EventHandling/Conceptual/EventHandlingiPhoneOS/Introduction/Introduction.html#//apple_ref/doc/uid/TP40009541

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It doesn't, it just draws and draws. The scrollView makes sure you only see the part you really want to see

You might want to look at three20, they have a class that is very similar to the springboard. -- Used in facebook.app

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Thanks Everyone, but I found out that UIScrollView sends the touchesCancelled message to the subview when scrolling starts.