React Native 開發豆瓣評分（八）首頁開發

首頁完成效果展現：javascript

<div style="text-align:center;"> <img src="https://img2018.cnblogs.com/blog/1312841/201907/1312841-20190718135309802-1875493361.gif" /> </div>java

1、開發佔位圖組件

在沒有數據的時候使用佔位圖替代 items 的位置。react

在 components 目錄裏建立 moviesItemPlaceholder.jsajax

import React, { Component } from 'react';
import { View, StyleSheet } from 'react-native';
import { px } from '../utils/device';

export default class MoviesItemPlaceholder extends Component {
    render() {
        const arr = [1, 2, 3, 4];
        return (
            <View style={styles.page}>
                {arr.map((index) => (
                    <View style={styles.placeholder} key={index}>
                        <View style={styles.img} />
                        <View style={styles.title} />
                        <View style={styles.rate} />
                    </View>
                ))}
            </View>
        )
    }
}

const styles = StyleSheet.create({
    page: {
        flexDirection: 'row',
        paddingLeft: px(30)
    },
    placeholder: {
        width: px(160),
        marginRight: px(16)
    },
    img: {
        width: px(160),
        height: px(224),
        overflow: 'hidden',
        borderRadius: px(8),
        backgroundColor: '#f8f8f8'
    },
    title: {
        marginTop: px(20),
        backgroundColor: '#f8f8f8',
        height: px(30),
        width: px(130),
        overflow: 'hidden',
        borderRadius: px(8)
    },
    rate: {
        marginTop: px(16),
        backgroundColor: '#f8f8f8',
        height: px(24),
        width: px(130),
        overflow: 'hidden',
        borderRadius: px(8)
    }
});

2、首頁數據請求

使用 postman 之類的工具能夠看到，首頁接口返回的數據字段大體同樣，數據均在 subject_collection_items 字段裏，能夠瘋轉一個方法量來請求數據。redux

var items = ['showing', 'hot', 'tv', 'variety', 'book', 'music'];
items.forEach(type => {
    this.getList(type);
});
getList = (type) => {
    ajax(type, {
      start: 0,
      count: 9
    }).then(value => {
      let state = {}
      state[type] = value.subject_collection_items;
      this.setState(state);
    })
  }

首頁頁面展現

縱向滑動，使用 ScrollView 組件；橫向滑動，使用 FlatList 組件，FlatList 組件的 ListEmptyComponent 表示沒有數據時顯示的組件，在這裏放置佔位圖組件；react-native

import React from "react";
import { View, Text, StatusBar, StyleSheet, ScrollView, FlatList, TouchableWithoutFeedback } from "react-native";
import { connect } from 'react-redux';
import ajax from "../utils/ajax";
import Header from '../components/header';
import ItemsHeader from '../components/itemsHeader';
import MoviesItem from '../components/moviesItem';
import MoviesItemPlaceholder from '../components/moviesItemPlaceholder';
import Icon from 'react-native-vector-icons/AntDesign';
import { px } from "../utils/device";

class Home extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      showing: [],
      hot: [],
      tv: [],
      variety: [],
      book: [],
      music: [],
    }
    var items = ['showing', 'hot', 'tv', 'variety', 'book', 'music'];
    items.forEach(type => {
      this.getList(type);
    });
  }
  getList = (type) => {
    ajax(type, {
      start: 0,
      count: 9
    }).then(value => {
      let state = {}
      state[type] = value.subject_collection_items;
      this.setState(state);
    })
  }
  render() {
    const { dispatch, value, navigation } = this.props;
    const { showing, hot, tv, variety, book, music } = this.state;
    const sections = [
      { title: '影院熱映', data: showing, type: 'showing' },
      { title: '豆瓣熱門', data: hot, type: 'hot' },
      { title: '近期熱門劇集', data: tv, type: 'tv' },
      { title: '近期熱門綜藝節目', data: variety, type: 'variety' },
      { title: '暢銷圖書', data: book, type: 'book' },
      { title: '熱門單曲榜', data: music, type: 'music' }
    ]
    return (
      <View style={styles.page}>
        <Header showBack={false} title='豆瓣評分' backgroundColor='#00b600' color='#fff' />
        <ScrollView>
          <View style={styles.search}>
            <TouchableWithoutFeedback onPress={() => alert('search')}>
              <View style={styles.searchView}>
                <Icon name='search1' size={px(30)} color='#ccc' />
                <Text style={styles.searchText}>搜索</Text>
              </View>
            </TouchableWithoutFeedback>
          </View>
          {sections.map((list, index) => (
            <View key={index} style={styles.list}>
              <ItemsHeader title={list.title} onPress={() => navigation.push('List', { data: list })} />
              <FlatList
                horizontal={true}
                data={list.data}
                keyExtractor={(item, index) => 'item' + index}
                ListEmptyComponent={() => <MoviesItemPlaceholder />}
                renderItem={({ item, index }) => (
                  <View style={{ marginRight: index !== showing.length - 1 ? px(16) : px(30), marginLeft: index === 0 ? px(30) : 0 }}>
                    <MoviesItem data={item} />
                  </View>
                )}
              />
            </View>
          ))}
        </ScrollView>
      </View>
    );
  }
}

const select = (store) => {
  return {
    value: store.num.value,
  }
}

export default connect(select)(Home);

const styles = StyleSheet.create({
  page: {
    flex: 1,
    backgroundColor: '#fff'
  },
  search: {
    backgroundColor: '#00b600',
    height: px(80),
    alignItems: 'center',
    justifyContent: 'center'
  },
  searchView: {
    height: px(50),
    width: px(710),
    borderRadius: px(8),
    backgroundColor: '#fff',
    flexDirection: 'row',
    justifyContent: 'center',
    alignItems: 'center'
  },
  searchText: {
    fontSize: px(26),
    color: '#ccc',
    marginLeft: px(6)
  },
  list: {
    marginBottom: px(30)
  }
});

4、緩存列表數據

當處於弱網環境時，打開應用，可能會顯示好久的佔位圖，此時咱們能夠將列表數據緩存至本地，每次進入應用先展現本地緩存的數據，而後請求數據，替換本地數據。緩存

此時，就可使用 redux 了。工具

編譯 reducer

爲了目錄整清晰點（讓 redux 相關的代碼文件都存儲於 store 目錄下），將 src 目錄下的 reducer 目錄移動到 store 目錄下，並在 reducer 目錄建立 list.js。post

const initList = {
    showing: [],
    hot: [],
    tv: [],
    variety: [],
    book: [],
    music: []
}

const setListState = (state = initList, action) => {
    switch (action.type) {
        case 'showing':
            return {
                ...state,
                showing: action.data
            }
        case 'hot':
            return {
                ...state,
                hot: action.data
            }
        case 'tv':
            return {
                ...state,
                tv: action.data
            }
        case 'variety':
            return {
                ...state,
                showing: action.data
            }
        case 'book':
            return {
                ...state,
                book: action.data
            }
        case 'music':
            return {
                ...state,
                music: action.data
            }
        default:
            return state;
    }
}

export default setListState;

在 reducer 的 index.js 中導入 setListState;flex

...
import setListState from './list';
...
export default combineReducers({
    ...
    list: setListState
    ...
});

修改 store/index.js 的路徑引入

import reducer from './reducer';

編輯 action

將以前src下的 action 目錄刪除，在 store 目錄下建立 action.js。

export function login(data) {
    return {
        type: 'login',
        data
    }
}

export function logout(data) {
    return {
        type: 'logout',
        data
    }
}

// set 首頁列表數據
export function setShowing(data) {
    return {
        type: 'showing',
        data
    }
}
export function setHot(data) {
    return {
        type: 'hot',
        data
    }
}
export function setTv(data) {
    return {
        type: 'tv',
        data
    }
}
export function setVariety(data) {
    return {
        type: 'variety',
        data
    }
}
export function setBook(data) {
    return {
        type: 'book',
        data
    }
}
export function setMusic(data) {
    return {
        type: 'music',
        data
    }
}

編輯首頁

導入修改 store 的方法：

import { setShowing, setHot, setTv, setVariety, setBook, setMusic } from '../store/action';

頁面獲取 store 存儲的數據：

const select = (store) => {
  return {
    showing: store.list.showing,
    hot: store.list.hot,
    tv: store.list.tv,
    variety: store.list.variety,
    book: store.list.book,
    music: store.list.music
  }
}
export default connect(select)(Home);

頁面獲取數據時，改變 store 裏的數據

因爲須要 save 數據，因此前面建立的 getList 和傳入的 items 須要作一些改變：

...
var items = [
    { type: 'showing', save: setShowing }, 
    { type: 'hot', save: setHot },
    { type: 'tv', save: setTv },
    { type: 'variety', save: setVariety },
    { type: 'book', save: setBook },
    { type: 'music', save: setmusic },
]
items.forEach(item => {
    this.getList(item);
});
...
getList = (item) => {
    ajax(item.type, {
      start: 0,
      count: 9
    }).then(value => {
      this.props.dispatch(item.save(value.subject_collection_items));
    })
  }

修改 render 裏的獲取數據方式：

render(){
    const { dispatch, value, navigation, showing, hot, tv, variety, book, music } = this.props;
    ...
}

至此，首頁算是開發完了。