react-native-intersection-observer

react-native-intersection-observer is a React Native implementation of Intersection Observer. An easier way to detect "View" exposure in complex application.

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Installation

npm install rn-intersection-observer

Requirements

This module was developed and tested with dependencies below. May also works fine with older versions that support "measureInWindow".

React >= 16.13.1

React-native >= 0.63.4

Usage

Target view

import { IntersectionObserverView } from 'rn-intersection-observer';

// ...

<IntersectionObserverView
    scope="YourOwnScope"
    thresholds={[0.8]}
    onIntersectionChange={onTagIntersectionChange}
>
 {/* your own view */}
</IntersectionObserverView>

Trigger detection from React Native

import { IntersectionObserver } from 'rn-intersection-observer';

// ...

const onScroll = useCallback(
    (event) => {
        IntersectionObserver.emitEvent('YourOwnScope');
    },
    [],
);

return (
    <ScrollView onScroll={onScroll}>
        {/* Scroll view contains IntersectionObserverView */}
    </ScrollView>
);

Trigger detection from Native (Android example)

getReactApplicationContext()
  .getJSModule(DeviceEventManagerModule.RCTDeviceEventEmitter.class)
  .emit("IntersectionObeserverEvent", { scope: 'YourOwnScope' });

Props & Params

1) IntersectionObserver / IntersectionObserverView

Props	Params Type	Description
scope	string	Scope of the target View, required in event trigger.
rootMargin	{top: number, left: number, bottom: number, right: number}	Distance from screen edge of detect area.
thresholds	number[]	Intersection ratios which should trigger intersection callbacks.
throttle	number	Throttle time between each detection(ms).

2) Intersection Callback (onIntersectionChange)

Callback parameter is an array containes info of each target which triggered intersection callback：

Params	Params Type	Description
boundingClientRect	{top: number, left: number, bottom: number, right: number}	Position of target View's edge.
intersectionRatio	number	Intersection ratio of target View in detect area
intersectionRect	{top: number, left: number, bottom: number, right: number}	Position of intersection area's edge.
target	Ref	Ref of target View
isInsecting	boolean	Determine current intersection ratio is larger than any threshold.

PS：Different from IntersectionObserver, IntersectionObserverView provides single parameter.

License

MIT