Vuex 是一个专为 Vue.js 应用程序开发的状态管理模式。它采用集中式存储管理应用的所有组件的状态，并以相应的规则保证状态以一种可预测的方式发生变化
播放器组件play.vue在多个组件中都有使用，因此放在app.vue中，同时基于vuex进行管理

1.组件放置在app.vue中

<template>
  <div id="app">
    <m-header></m-header>
    <tab></tab>
    <keep-alive>
      <router-view></router-view>
    </keep-alive>
    <player></player>
  </div>
</template>

2.state.js定义状态

import {playMode} from 'common/js/config'
const state = {
  singer: {},                    
  playing: false,             //playing: 播放状态
  fullScreen: false,          //fullScreen: 是否全屏（normal播放器/mini播放器）
  playlist: [],               //点击前进、后退实际是有一个播放列表：playlist
  sequenceList: [],           //sequenceList顺序播放列表
  mode: playMode.sequence,    //mode:播放模式  0顺序  1 循环  2 随机
  currentIndex: -1,           //currentIndex 当前播放的歌曲
  disc: {},
  topList: {}
}
export default state

3.获取state的一些状态getter.js

需要从 store 中的 state 中派生出一些状态，Vuex 允许我们在 store 中定义“getter”（可以认为是 store 的计算属性）

export const singer = state => state.singer
export const playing = state => state.playing
export const fullScreen = state => state.fullScreen
export const playlist = state => state.playlist
export const sequenceList = state => state.sequenceList
export const mode = state => state.mode
export const currentIndex = state => state.currentIndex
export const currentSong = (state) => {
  return state.playlist[state.currentIndex] || {}
}

export const disc = state => state.disc
export const topList = state => state.topList

4.mutations.js

更改 Vuex 的 store 中的状态的唯一方法是提交 mutation

//使用常量替代 mutation 事件类型在各种 Flux 实现中是很常见的模式。
//这样可以使 linter 之类的工具发挥作用，同时把这些常量放在单独的文件中可以让你的代码合作者对整个 app 包含的 mutation 一目了然
export const SET_SINGER = 'SET_SINGER'
export const SET_PLAYING_STATE = 'SET_PLAYING_STATE'
export const SET_FULL_SCREEN = 'SET_FULL_SCREEN'
export const SET_PLAYLIST = 'SET_PLAYLIST'
export const SET_SEQUENCE_LIST = 'SET_SEQUENCE_LIST'
export const SET_PLAY_MODE = 'SET_PLAY_MODE'
export const SET_CURRENT_INDEX = 'SET_CURRENT_INDEX'

export const SET_DISC = 'SET_DISC'

export const SET_TOP_LIST = 'SET_TOP_LIST'

import * as types from './mutation-types'

const mutations = {
  [types.SET_SINGER](state, singer) {
    state.singer = singer
  },
  [types.SET_PLAYING_STATE](state, flag) {
    state.playing = flag
  },
  [types.SET_FULL_SCREEN](state, flag) {
    state.fullScreen = flag
  },
  [types.SET_PLAYLIST](state, list) {
    state.playlist = list
  },
  [types.SET_SEQUENCE_LIST](state, list) {
    state.sequenceList = list
  },
  [types.SET_PLAY_MODE](state, mode) {
    state.mode = mode
  },
  [types.SET_CURRENT_INDEX](state, index) {
    state.currentIndex = index
  },
  [types.SET_DISC](state, disc) {
    state.disc = disc
  },
  [types.SET_TOP_LIST](state, topList) {
    state.topList = topList
  }
}

export default mutations

5.actions.js

actions应用场景：

1. 异步操作
2. 封装多个mutations更改state

6.界面