HeaderStyleInterpolator.js
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import { I18nManager } from 'react-native';
import getSceneIndicesForInterpolationInputRange from '../../utils/getSceneIndicesForInterpolationInputRange';
/**
* Utility that builds the style for the navigation header.
*
* +-------------+-------------+-------------+
* | | | |
* | Left | Title | Right |
* | Component | Component | Component |
* | | | |
* +-------------+-------------+-------------+
*/
function forLeft(props) {
const { position, scene, scenes } = props;
const interpolate = getSceneIndicesForInterpolationInputRange(props);
if (!interpolate) return { opacity: 0 };
const { first, last } = interpolate;
const index = scene.index;
return {
opacity: position.interpolate({
inputRange: [first, first + Math.abs(index - first) / 2, index, last - Math.abs(last - index) / 2, last],
outputRange: [0, 0, 1, 0, 0]
})
};
}
function forCenter(props) {
const { position, scene } = props;
const interpolate = getSceneIndicesForInterpolationInputRange(props);
if (!interpolate) return { opacity: 0 };
const { first, last } = interpolate;
const index = scene.index;
const inputRange = [first, index, last];
return {
opacity: position.interpolate({
inputRange,
outputRange: [0, 1, 0]
}),
transform: [{
translateX: position.interpolate({
inputRange,
outputRange: I18nManager.isRTL ? [-200, 0, 200] : [200, 0, -200]
})
}]
};
}
function forRight(props) {
const { position, scene } = props;
const interpolate = getSceneIndicesForInterpolationInputRange(props);
if (!interpolate) return { opacity: 0 };
const { first, last } = interpolate;
const index = scene.index;
return {
opacity: position.interpolate({
inputRange: [first, index, last],
outputRange: [0, 1, 0]
})
};
}
export default {
forLeft,
forCenter,
forRight
};