Gesture Handler

State flow

• Interactive demo

State

Every gesture can be treated as a state machine. That is, each handler instance has its own assigned state that can change when new touch events occur.

A gesture can be in one of 6 possible states

1. undetermined
2. failed
3. began
4. cancelled
5. active
6. end

Events

There are three types of events:

1. StateChangeEvent - sent every time a gesture moves to a different state
2. GestureEvent - sent every time a gesture is updated
3. PointerEvent - carries information about raw touch events, like touching the screen or moving the finger.

Composing Gestures

• docs

Composing gestures means determining how multiple gestures interact with each other.

The Gesture object provides 3 methods to do this:

1. Race - The first gesture to have an active state will cancel the rest of the gestures on deck

• ex. in Tinder, you can swipe left or right on a picture, but if you long press then you'll 'Heart' the profile.

2. Simultaneous - All of the gestures can be active at the same time
3. Exclusive - Only one of the gestures can be active, with the first one having higher priority than the second.