React-Native 选项卡简单实现

版本基于0.50.4,因0.50.0~0.50.3 安卓有一个horizontal的bug

先看图

Untitled4.gif

上面的部分用FlatList
下面部分用的是ScrollView

代码如下:

'use strict';

import React, {Component} from 'react';
import {
    StyleSheet,
    View,
    Text,
    ScrollView,
    FlatList,
    Dimensions,
    TouchableOpacity
} from 'react-native';

const tab_w = 100;

const tab_marigin = 10;

const colorAry = ['gray', 'green', 'blue', 'yellow', 'black', 'orange', 'black', 'yellow', 'blue', 'green']

const WIDTH = Dimensions.get('window').width;

const max_w = (tab_w + tab_marigin) * colorAry.length;


export default class HOME extends React.Component {

    constructor(props) {
        super(props);

        if (this.props.TabWidth) {
            this.WIDTH = this.props.TabWidth;
        } else {
            this.WIDTH = WIDTH;
        }

        this.state = {
            tabArr: [],
        };

    };

    componentDidMount() {
        this._setIndex(0);
    }


    render() {
        return (
            
                
                     this._flatList = flatList}
                        renderItem={this._renderTabItem}
                        horizontal={true}
                        data={this.state.tabArr}
                        keyExtractor={(v, i) => i}
                    />
                

                
                     this._scrollView = scrollView}
                                horizontal={true}
                                pagingEnabled={true}
                                onMomentumScrollEnd={this._onAnimationEnd}
                    >
                        {this._renderItem()}
                    
                

            
        );
    }

    _renderItem() {
        // 数组
        let itemAry = [];
        // 颜色数组
        // 遍历
        for (let i = 0; i < colorAry.length; i++) {
            itemAry.push(
                
            );
        }
        return itemAry;
    }

    _renderTabItem = (data, index) => {

        if (data.item.selected) {
            return (
                 this._tabClick(data.item.index)}>

                    
                        {data.item.title}
                        
                    
                
            );
        } else {
            return (
                 this._tabClick(data.item.index)}>

                    
                        {data.item.title}
                    
                

            );
        }
    }

    _tabClick(index) {
        this._tabScrollToIndex(index);
        this._scrollView.scrollTo({x: index * WIDTH, y: 0, animated:true});
    }


    _onAnimationEnd = (e) => {
        var offset = e.nativeEvent.contentOffset.x;

        if (offset < 0) {
            return;
        }

        var currentX = Math.floor(offset / WIDTH);

        this._tabScrollToIndex(currentX);


    }


    _tabScrollToIndex(index){

        this._setIndex(index);

        var centerX = this.WIDTH / 2.0;

        var tabOffset = index * (tab_w + tab_marigin)


        var itemX = tabOffset + tab_w / 2.0;

        var scrollX = itemX - centerX;


        if (scrollX < 0) {
            scrollX = 0;
        }

        if (scrollX >= max_w - this.WIDTH) {
            scrollX = max_w - this.WIDTH;
        }


        this._flatList.scrollToOffset({offset: scrollX})
    }

    _setIndex(index) {
        if (index >= colorAry.length) {
            return;
        }
        let arr = [];
        for (let i = 0; i < colorAry.length; i++) {
            let tabItem;
            if (i == index) {
                tabItem = {
                    title: colorAry[i],
                    index: i,
                    selected: true
                }
            } else {
                tabItem = {
                    title: colorAry[i],
                    index: i,
                    selected: false
                }
            }


            arr.push(
                tabItem
            );
        }


        this.setState({
            tabArr: arr,
        });
    }

}

const styles = StyleSheet.create({
    container: {
        flex: 1,
        backgroundColor: '#dddddd',
    },
    scrollViewStyle: {
        // 背景色
        backgroundColor: 'red'
    },
    itemStyle: {
        // 尺寸
        width: WIDTH,
        height: 300
    },
});