When building interactive elements like color swatches or buttons, the order in which events trigger is vital for a responsive user experience. By separating visual feedback from data operations, you can significantly improve the perceived performance of your application.
Separate Visuals from Data
A common mistake is to handle both the visual "selected" state and the data fetching on a single event. This can lead to a "laggy" feel where the user taps an item, but nothing appears to happen while the application waits for an API response.
To solve this, split your logic across two specific events:
- On Press In: Use this event to trigger an immediate visual change, such as applying a selected border or a darker background color. This provides instant feedback, confirming to the user that their interaction was successful.
- On Press: Use this event to trigger the main Flow that fetches data or navigates to a new screen. Because the user has already seen a visual response from the On Press In event, the time spent waiting for data feels shorter.
Understanding the Responder Chain
The sequence of these events mirrors the natural "responder chain" of mobile devices:
- Initiation (On Press In): The finger touches the screen.
- Completion (On Press): The finger is lifted from the screen.
Using On Press In for UI updates creates an "optimistic" interface that feels fast and intentional, even when working with complex background logic or slower network conditions.