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ScrollableTabBar.js
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ScrollableTabBar.js
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const React = require('react');
const ReactNative = require('react-native');
const {
View,
Animated,
StyleSheet,
ScrollView,
TouchableOpacity,
Text,
Platform,
findNodeHandle,
Dimensions,
} = ReactNative;
const TAB_HEIGHT = 50;
const WINDOW_WIDTH = Dimensions.get('window').width;
const ScrollableTabBar = React.createClass({
getDefaultProps() {
return {
scrollOffset: 52,
};
},
propTypes: {
goToPage: React.PropTypes.func,
activeTab: React.PropTypes.number,
tabs: React.PropTypes.array,
underlineColor: React.PropTypes.string,
underlineHeight: React.PropTypes.number,
backgroundColor: React.PropTypes.string,
activeTextColor: React.PropTypes.string,
inactiveTextColor: React.PropTypes.string,
scrollOffset: React.PropTypes.number,
},
getInitialState() {
this._tabsMeasurements = [];
return {
_leftTabUnderline: new Animated.Value(0),
_widthTabUnderline: new Animated.Value(0),
_containerWidth: null,
};
},
updateView(offset) {
const position = Math.floor(offset.value);
const pageOffset = offset.value % 1;
const tabCount = this.props.tabs.length;
if (tabCount === 0 || offset.value < 0 || offset.value > tabCount - 1) {
return;
}
if (this.necessarilyMeasurementsCompleted(position)) {
this.updateTabPanel(position, pageOffset);
this.updateTabUnderline(position, pageOffset, tabCount);
}
},
necessarilyMeasurementsCompleted(position) {
return this._tabsMeasurements[position] && this._tabsMeasurements[position + 1];
},
updateTabPanel(position, pageOffset) {
const absolutePageOffset = pageOffset * this._tabsMeasurements[position].width;
let newScrollX = this._tabsMeasurements[position].left + absolutePageOffset;
newScrollX -= this.props.scrollOffset;
newScrollX = newScrollX >= 0 ? newScrollX : 0;
if (Platform === 'android') {
this._scrollView.scrollTo({x: newScrollX, y: 0, });
} else {
const rightBoundScroll = this._tabContainerMeasurements.width - (this._containerMeasurements.width);
newScrollX = newScrollX > rightBoundScroll ? rightBoundScroll : newScrollX;
this._scrollView.scrollTo({x: newScrollX, y: 0, });
}
},
updateTabUnderline(position, pageOffset, tabCount) {
const lineLeft = this._tabsMeasurements[position].left;
const lineRight = this._tabsMeasurements[position].right;
if (position < tabCount - 1) {
const nextTabLeft = this._tabsMeasurements[position + 1].left;
const nextTabRight = this._tabsMeasurements[position + 1].right;
const newLineLeft = (pageOffset * nextTabLeft + (1 - pageOffset) * lineLeft);
const newLineRight = (pageOffset * nextTabRight + (1 - pageOffset) * lineRight);
this.state._leftTabUnderline.setValue(newLineLeft);
this.state._widthTabUnderline.setValue(newLineRight - newLineLeft);
} else {
this.state._leftTabUnderline.setValue(lineLeft);
this.state._widthTabUnderline.setValue(lineRight - lineLeft);
}
},
renderTabOption(name, page) {
const isTabActive = this.props.activeTab === page;
const activeTextColor = this.props.activeTextColor || 'navy';
const inactiveTextColor = this.props.inactiveTextColor || 'black';
const textStyle = this.props.textStyle || {};
return <TouchableOpacity
key={name}
ref={'tab_' + page}
accessible={true}
accessibilityLabel={name}
accessibilityTraits='button'
style={styles.tab}
onPress={() => this.props.goToPage(page)}
onLayout={this.measureTab.bind(this, page)}
>
<View>
<Text style={[{color: isTabActive ? activeTextColor : inactiveTextColor}, textStyle]}>{name}</Text>
</View>
</TouchableOpacity>;
},
measureTab(page) {
const tabContainerhandle = findNodeHandle(this.refs.tabContainer);
this.refs['tab_' + page].measureLayout(tabContainerhandle, (ox, oy, width, height, pageX, pageY) => {
this._tabsMeasurements[page] = {left: ox, right: ox + width, width: width, height: height, };
this.updateView({value: this.props.scrollValue._value, });
});
},
render() {
const tabUnderlineStyle = {
position: 'absolute',
height: this.props.underlineHeight || 4,
backgroundColor: this.props.underlineColor || 'navy',
bottom: 0,
};
this.props.scrollValue.addListener(this.updateView);
const dynamicTabUnderline = {
left: this.state._leftTabUnderline,
width: this.state._widthTabUnderline,
};
return <View
style={[styles.container, {backgroundColor: this.props.backgroundColor || null, }, ]}
onLayout={this.onContainerLayout}
>
<ScrollView
ref={(scrollView) => { this._scrollView = scrollView; }}
horizontal={true}
showsHorizontalScrollIndicator={false}
showsVerticalScrollIndicator={false}
style={styles.scrollableContainer}
directionalLockEnabled={true}
scrollEventThrottle={16}
>
<View
style={[styles.tabs, {width: this.state._containerWidth}]}
ref={'tabContainer'}
onLayout={this.onTabContainerLayout}
>
{this.props.tabs.map((tab, i) => this.renderTabOption(tab, i))}
<Animated.View style={[tabUnderlineStyle, dynamicTabUnderline, ]} />
</View>
</ScrollView>
</View>;
},
onTabContainerLayout(e) {
this._tabContainerMeasurements = e.nativeEvent.layout;
let width = this._tabContainerMeasurements.width;
if(width < WINDOW_WIDTH){
width = WINDOW_WIDTH;
}
this.setState({
_containerWidth: width,
})
},
onContainerLayout(e) {
this._containerMeasurements = e.nativeEvent.layout;
},
});
module.exports = ScrollableTabBar;
const styles = StyleSheet.create({
tab: {
height: TAB_HEIGHT - 1,
alignItems: 'center',
justifyContent: 'center',
paddingBottom: 30,
paddingLeft: 20,
paddingRight: 20,
},
container: {
height: TAB_HEIGHT,
borderWidth: 1,
borderTopWidth: 0,
borderLeftWidth: 0,
borderRightWidth: 0,
borderBottomColor: '#ccc',
},
tabs: {
height: TAB_HEIGHT - 1,
flexDirection: 'row',
justifyContent: 'space-around',
},
scrollableContainer: {
height: TAB_HEIGHT,
},
});