How does iOS event handling flow work (touch system)?

Updated May 17, 2026

Short answer

Touch events flow from UIApplication → UIWindow → UIView hierarchy using responder chain.

Deep explanation

When a touch occurs, UIKit creates a UIEvent and sends it to UIApplication, which passes it to the correct UIWindow. The hit-testing system determines which UIView should receive the event, and then responder chain methods like touchesBegan: are triggered.

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