What is the touches canceled event, and how is it different from touches ended

I just don't understand what apple means by the开发者_运维问答 touches canceled event and how is it called.

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I'm not really sure Tim addressed your question so I'll take a shot at it.

touchesCanceled is called when the OS needs to interrupt the user. It gives you a chance to clean up whatever you've been doing in touchesBegan and touchesMoved.

More specifically, it is called when the user puts the phone to his/her face turning the screen off, or if a notification like incoming call or new text message occurs.