react-native-pull-to-refresh-custom

Custom pull to refresh Header supporting for React Native ScrollView/FlatList

React Native 自定义下拉刷新Header

Online Expo demo here: https://snack.expo.io/@sophister/custom-pull-to-refresh-header

WARN: use at your own risk!

Show Case

Install

npm i react-native-pull-to-refresh-custom

Usage

Notice: It is only tested with react-native@0.59.3 and react-native@0.61.2.

PullToRefresh component can ONLY accept a single child, which must be one of ScrollView, FlatList. (I've only tested it with these two components. Theoretically, it should work with other Scrollable components such as SectionList).

//Props interface for PullToRefresh
interface PullToRefreshProps {
    // container's style. You should give it a `backgroundColor`, without it,
    // the PanResponder will be terminated on iOS, according to my test
    style: ViewStyle;
    // your custom Header component, it will receive props of  PullToRefreshHeaderProps
    HeaderComponent: ComponentType<PullToRefreshHeaderProps & RefAttributes<any>>;
    // Header component's height
    headerHeight: number;
    // pulling height to trigger `onRefresh` callback, default to `headerHeight`
    refreshTriggerHeight?: number;
    // container's sticky top position when `refreshing` is true, default to `headerHeight`
    refreshingHoldHeight?: number;
    // is refreshing
    refreshing: boolean;
    // parent's callback if user's pull distance trigger a refreshing
    onRefresh: () => void;
    // child component
    children: JSX.Element;
    // when the inner scrollable's contentOffset.y <= topPullThreshold,
    // pulling down will trigger container's translate
    topPullThreshold: number;
}

// Header component's Props interface
interface PullToRefreshHeaderProps {
    // current pull distance of container component
    pullDistance: number;
    // current pull ratio range of [0, 1]
    percentAnimatedValue: Animated.AnimatedDivision;
    // current pull ratio, range of [0, 1]
    percent: number;
    // is currently refreshing
    refreshing: boolean;
}

import PullToRefresh, { PullToRefreshHeaderProps } from 'react-native-pull-to-refresh-custom';

class Header extends Component {
    // Header component **MUST** expose a `setProgress` method,
    // which is called when user is pulling container down
    // pullDistance is user's pull distance
    // percent is current pull ratio range of [0, 1]
    setProgress({ pullDistance, percent }: { pullDistance: number; percent: number}) {
        this.setState({
            pullDistance,
            percent,
        });
    }
}

<PullToRefresh
    HeaderComponent={Header}
    headerHeight={100}
    refreshTriggerHeight={140}
    refreshingHoldHeight={140}
    refreshing={this.state.refreshing}
    onRefresh={this.onRefresh}
    style={{ flex: 1, backgroundColor: 'red' }}
>
    <FlatList
        style={{ flex: 1 }}
        scrollEventThrottle={20}
        {...otherProps}
    />
</PullToRefresh>

Header component WARNING

Your custom Header component, MUST have a method called setProgress!

Your custom Header component, MUST have a method called setProgress!

Your custom Header component, MUST have a method called setProgress!

But why?

I've tried to pass the pullDistance and percent to header component through the traditional React's props flow. To do so, I've to keep pullDistance on PullToRefresh's state, and call setState() every time when user is pulling down the container. But it results in a janky animation. So, I decide to pass pullDistance to the header component through a method call.

PullToRefresh style WARNING

When I test PullToRefresh component on iOS, the container's pan responder will be terminated after it is granted, if I don't give it a backgroundColor. So, PullToRefresh will have a white background color default.

Implementation detail

Basically, PullTeRefresh is just a wrapper, the view hierarchy is simple like below:

<View>
    <Animated.View>
        <YourCustomHeader />
    </Animated.View>
    <FlatList />
</View>

Your custom Header component is within an Animated.View, which is absolute positioned with top equals - props.headerHeight, so that the header is not visible by default.

PullToRefresh has a property to track the scroll position of inner FlatList. When the inner FlatList's scrollTop is <= topPullThreshold (which defaults to 2), and if user tries to pull down, the container will catch user's drag action. Along user pulling down, it translates the Animated.View into visible region, and passes the pullDistance and percent to your custom Header component constantly through calling Header's setProgress directly.

When user releases their finger, PullToRefresh will check current pullDistance. If it's >= props.refreshTriggerHeight, it will call props.onRefresh; otherwise, it will animate the Animated.View back to it's hidden position.

sophister/react-native-pull-to-refresh-custom

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