The Evolution of Pointer Events: Enhancing Cross-Platform App Development
In the pre-smartphone era, the mouse was the primary pointing input device. With the advent of smartphones, touch became the preferred interaction method. Today, we have pens, desktops, and laptops with touch screens, making it essential to consider various types of events when building cross-platform apps.
A Brief History of Pointer Events
Pointer events were designed to be hardware-agnostic, targeting specific screen coordinates. This innovation makes developing cross-platform apps much easier, as you can use a single event model to handle touch inputs, mouse inputs, multi-touch, and pen inputs. The Pointer Events API in React Native is based on the W3C pointer events API, providing a unified way to handle events from different devices.
The React Native Pointer Events Prop
Before diving into implementation, let’s explore the pointerEvents prop. This prop not only activates and deactivates pointer events in a React Native View but also does the same for touch events. It has four possible values:
auto: The View and its children can be the target of touch and pointer events.none: Neither the View nor its children can be the target of touch and pointer events.box-only: The View can be the target of touch and pointer events, but not its children.box-none: The View’s children can be the target of touch and pointer events, but not the View itself.
Currently Available React Native Pointer Events
The React Native Pointer Events API is still a work in progress. Currently, the following events have been implemented:
onPointerOver: Fires when the user’s pointer enters the bounds of a View.onPointerEnter: Fires when the user’s pointer enters the bounds of a View and moves inside those bounds.onPointerDown: Fires when the user presses down on the screen with their pointer.onPointerMove: Fires when the user moves their pointer while it is still pressed down.onPointerUp: Fires when the user releases the pressure on the screen after having pressed down with their pointer.onPointerOut: Fires when the user’s pointer exits the bounds of a View.onPointerLeave: Fires when the user’s pointer enters the bounds of a View, but then moves outside those bounds without interacting with the View.
Implementing React Native Fabric for Pointer Events
To use pointer events, you need to enable Fabric, React Native’s new rendering engine, which is only available in version ≥ 0.71 of React Native. Fabric requires a few extra steps to activate the feature flags.
Activating the Pointer Events Feature Flag
To use pointer events, you need to enable the shouldEmitW3CPointerEvents feature flag in your JavaScript code, as well as in iOS and Android.
React Native Pointer Event Use Cases
Pointer events have various use cases, similar to those for mouse events, touch events, and other pointing devices. Some examples include:
- Detecting Pointer Type: Determine the type of pointer device and find the x and y offset of the event in the View.
- Drawing Apps: Create a drawing app using the React Native SVG package and pointer events to create a path in an SVG image.
- Drag-and-Drop Functionality: While pointer capture is not yet available, you can use PanResponder for drag-and-drop use cases.
Conclusion
React Native’s Pointer Events API provides a powerful way to handle input events from different devices on both Android and iOS platforms. Although the API is still experimental and requires enabling Fabric, it will eventually provide a much simpler way to handle pointer events. With its hardware-agnostic design and single event model, pointer events make developing React Native apps simpler and more flexible.