【音乐App】—— Vue-music 项目学习笔记：歌曲列表组件开发

前言：以下内容均为学习慕课网高级实战课程的实践爬坑笔记。

项目github地址：https://github.com/66Web/ljq_vue_music，欢迎Star。

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当前歌曲播放列表	添加歌曲到队列

components->playlist目录下：创建playlist.vue -- 在play.vue中应用

一、.歌曲列表组件显示和隐藏的控制

• data中维护一个数据 

  showFlag: false

• 使用v-show判断showFlag控制显示隐藏

  <div class="playlist" v-show="showFlag">

• methods中分别定义show()和hide()，设置showFlag为true和false

  show() {
      this.showFlag = true
  },
  hide() {
      this.showFlag = false
  }

• player.vue中:给列表按钮添加点击事件，并阻止事件冒泡，showPlaylist方法执行playlist中的show()控制列表的显示

  <div class="control" @click.stop.prevent="showPlaylist">
  <play-list ref="playlist">

  showPlaylist() {
      this.$refs.playlist.show()
  }

• playlist.vue中：给列表的蒙层和关闭按钮都添加点击事件，触发hide方法，控制列表的隐藏

• 坑：点击列表本身也会关闭列表
• 原因：给列表蒙层添加点击事件时，实际上添加到了最外层<div class="playlist">上，点击子元素时会事件冒泡到最外层
• 解决：给list-wrapper添加@click.stop，阻止点击事件冒泡 

  <div class="list-wrapper" @click.stop>

二、歌曲列表组件播放列表的实现

• 通过mapGetters获取顺序播放的歌曲列表添加到列表项

  import {mapGetters} from 'vuex'
  
  computed: {
      ...mapGetters([
         'sequenceList'
     ])
  }

  <li class="item" v-for="(item, index) in sequenceList" :key="index">
      <span class="text">{{item.name}}</span>

• 应用Scroll组件实现歌曲列表滚动

  <scroll class="list-content" :data="sequenceList" ref="listContent">

• 在show()时让scroll重新进行计算，确保当前高度是正确的

  show() {
      this.showFlag = true
      setTimeout(() => {
           this.$refs.listContent.refresh()
      }, 20)
  }

• 给当前播放的歌曲添加current高亮显示的样式

  <i class="current" :class="getCurrentIcon(item)"></i>

  通过mapGetters获取当前歌曲： 'currentSong'

  getCurrentIcon(item) {
      if(this.currentSong.id === item.id) {
          return 'icon-play'
      }
      return ''
  }

• 选择列表项播放歌曲

  <li class="item" @click="selectItem(item, index)">

  通过mapGetters获得currentSong和playlist，通过mapMutations调用setCurrentIndex提交数据

  import {playMode} from '@/common/js/config'
  
  computed: {
      ...mapGetters([
           'sequenceList',
           'currentSong',
           'playlist',
           'mode'
     ])
  }
  
  selectItem(item, index){
      //如果当前是随机播放，重新计算index
      if(this.mode === playMode.random) {
         inde = this.playlist.findIndex((song) => {
               return song.id === item.id
         })
     } 
     this.setCurrentIndex(index)
     this.setPlayingState(true)
  }
  
  ...mapMutations({
     setCurrentIndex: 'SET_CURRENT_INDEX',
     setPlayingState: 'SET_PLAYING_STATE'
  }) 

• 歌曲列表滚动到当前播放的歌曲

1. 需求：切换歌曲时，歌曲列表滚动到当前播放的歌曲位置；打开歌曲列表时，当前播放的歌曲始终在第一行显示
2. 封装一个滚动到当前播放歌曲的方法

   scrollToCurrent(current) {
      //找到当前歌曲在顺序列表中的索引
      const index = this.sequenceList.findIndex((song) => {
            return current.id === song.id
      })
      this.$refs.listContent.scrollToElement(this.$refs.listItem[index], 300)
   }

3. 切换歌曲成功时调用

   watch: {
       currentSong(newSong, oldSong) {
           if(!this.showFlag || newSong.id === oldSong.id) {
              return
          }
          this.scrollToCurrent(newSong)
      }
   }

4. 歌曲列表显示时调用

   show() {
       this.showFlag = true
       setTimeout(() => {
            this.$refs.listContent.refresh()
            this.scrollToCurrent(this.currentSong)
       }, 20)
   }

• 从歌曲播放列表中删掉所选歌曲

  <span class="delete" @click.stop="deleteOne(item)">

1. actions.js中：封装deleteSong()

   export const deleteSong = function ({commit, state}, song){
       let playlist = state.playlist.slice() //副本
       let sequenceList = state.sequenceList.slice() //副本
       let currentIndex = state.currentIndex
   
       let pIndex = findIndex(playlist, song)
       playlist.splice(pIndex, 1)
   
       let sIndex = findIndex(sequenceList, song)
       sequenceList.splice(sIndex, 1)
   
       if(currentIndex > pIndex || currentIndex === playlist.length){
          currentIndex--
       }
       commit(types.SET_PLAYLIST, playlist)
       commit(types.SET_SEQUENCE_LIST, sequenceList)
       commit(types.SET_CURRENT_INDEX, currentIndex)
   
       const playingState = playlist.length > 0
       commit(types.SET_PLAYING_STATE,playingState)
   }

2. 通过mapActions获取deleteSong方法

   ...mapActions([
       'deleteSong'
   ])

3. methods中定义deleteOne()，调用deleteSong()

   deleteOne(item) {
      this.deleteSong(item)
      if(!this.playlist.length){
         this.hide()
      } 
   }

4. 坑：报错this.currentSong.getLyric is not a function
5. 原因： action deleteSong修改了playlist和currentIndex，导致currentSong发生变化；在player.vue中的watch会监测到currentSong变化了，但其实这里列表中已经没有歌曲了；newSong为空的Object，此时将newSong和oldSong进行对比，都会返回undefined，所以报错
6. 解决：在watch currentSong()中判断如果没有newSong.id，直接返回，不执行任何操作

   if(!newSong.id) {
      return
   }

• 优化：给删除歌曲添加动画

1. 将<ul>替换为

   <transition-group name="list" tag="ul">

2. transition-group的关键: 内容<li class="item">必须要有 :key="index"

   .item
      height: 40px
      &.list-enter-active, &.list-leave-active
         transition: all 0.1s
      &.list-enter, &.list-leave-to
         height: 0

• 清除歌曲播放列表

1. 同搜索历史列表，在点击清除按钮后，需要先显示一个confirm弹窗，然后选择确认或取消
2. 给清空按钮添加点击事件，显示弹窗：

   <span class="clear" @click="showConfirm">

   showConfirm() {
       this.$refs.confirm.show()
   }

3. 给弹窗监听confirm事件，同时封装action，在confirm()中调用

   <confirm ref="confirm" text="是否清空播放列表" confirmBtnText="清空"
            @confirm="confirmClear"></confirm>

   confirmClear() {
      this.deleteSongList()
      this.hide()
   }
   ...mapActions([
      'deleteSong',
      'deleteSongList'
   ])

   actions.js中：

   export const deleteSongList = function ({commit}){
      //将所有值都重置为初始状态
      commit(types.SET_PLAYLIST, [])
      commit(types.SET_SEQUENCE_LIST, [])
      commit(types.SET_CURRENT_INDEX, -1)
      commit(types.SET_PLAYING_STATE, false)
   }

4. 坑：点击取消时，歌曲播放列表也会被关闭
5. 原因：在playlist.vue中<confirm>在<div class="playlist" @click="hide">内，点击confirm会事件冒泡，触发hide
6. 解决：让confirm组件更加独立，阻止事件冒泡 

   <div class="confirm" v-show="showFlag" @click.stop>

三、playerMixin的抽象

• 需求：歌曲播放列表中的播放模式切换功能与播放器中的逻辑相同，可以使用Mixin复用

• mixin.js中：创建新的playerMixin对象

  import {mapGetters, mapMutations} from 'vuex'
  import {playMode} from '@/common/js/config'
  import {shuffle} from '@/common/js/util'
  
  export const playerMixin = {
      computed: {
          iconMode(){
              return this.mode === playMode.sequence ? 'icon-sequence' : this.mode === 
  playMode.loop ? 'icon-loop' : 'icon-random'
          },
         ...mapGetters([
              'sequenceList',
              'currentSong',
              'playlist',
              'mode'
          ])
     },
     methods: {
        changeMode(){
              const mode = (this.mode + 1) % 3
              this.setPlayMode(mode)
              let list = null
              if(mode === playMode.random){
                 list = shuffle(this.sequenceList)
              }else{
                 list = this.sequenceList
              }
              this.resetCurrentIndex(list)
              this.setPlayList(list)
       },
       resetCurrentIndex(list){
              let index = list.findIndex((item) => { //es6语法
                   return item.id === this.currentSong.id
              })
              this.setCurrentIndex(index)
       },
       ...mapMutations({
              setPlayingState: 'SET_PLAYING_STATE',
              setCurrentIndex: 'SET_CURRENT_INDEX',
              setPlayMode: 'SET_PLAY_MODE',
              setPlayList: 'SET_PLAYLIST'
       })
     }
  }

• player和playlist中：应用playerMixin，同时删掉共用部分

  import {playerMixin} from '@/common/js/mixin'
  
  mixins:[playerMixin],

• playlist.vue中：动态绑定class，监听点击事件

  <i class="icon" :class="iconMode" @click="changeMode">

  computed: {
     modeText() {
         return this.mode === playMode.sequence ? '顺序播放' : this.mode === playMode.random ? '随机播放' : '单曲循环'
     }
  }

四、添加歌曲到列表add-song组件实现

• components->add-song目录下：创建add-song.vue

• 页面的显示隐藏：同playlist.vue

• 搜索框和搜索结果：与search.vue共有一些相同的逻辑，使用mixin复用

1. mixin.js中创建新的searchMixin对象

   export const searchMixin = {
       computed: {
          ...mapGetters([
            'searchHistory'
         ])
       },
      data() {
         return {
              query: ''
         }
      },
      methods: {
         blurInput() {
             this.$refs.searchBox.blur()
         },
         saveSearch() {
             this.saveSearchHistory(this.query)
         },
         onQueryChange(query){
             this.query = query
         },
         addQuery(query) {
             this.$refs.searchBox.setQuery(query)
         },
         ...mapActions([
             'saveSearchHistory',
             'deleteSearchHistory'
         ])
      }
   }

2. search和add-song中：应用searchMixin，同时删掉共用部分

   import {searchMixin} from '@/common/js/mixin'
   
   mixins:[searchMixin],

3. add-song.vue中：绑定数据，监听事件

   <search-box ref="searchBox" @query="onQueryChange" placeholder="搜索歌曲">
   <suggest :query="query" :showSinger="showSinger" @select="selectSuggest" @listScroll="blurInput">

• 切换Tab组件

1. base->switches目录下：创建switches.vue

   <li class="switch-item" v-for="(item, index) in switches" :key="index"
       :class="{'active': currentIndex === index}" @click="switchItem(index)">
       <span>{{item.name}}</span>
   </li>

   props: {
       switches: {
           type: Array,
           default: []
       },
       currentIndex: {
           type: Number,
           default: 0
       }
   },
   methods: {
       switchItem(index) {
           this.$emit('switch', index)
       }
   }

2. add-song.vue中应用：

   <switches :switches="switches" :currentIndex="currentIndex" @switch="switchItem"></switches>

   currentIndex: 0,
   switches: [
       {name: '最近播放'},
       {name: '搜索历史'}
   ]
   switchItem(index) {
       this.currentIndex = index
   }

• 最近播放列表

1. Vuex管理数据

   ①states.js中：添加数据

   playHistory: []

   ②mutations-types.js中：定义事件类型常量

   export const SET_PLAY_HISTORY = 'SET_PLAY_HISTORY'

   ③mutations.js中：创建方法

   [types.SET_PLAY_HISTORY](state, history){
      state.playHistory = history
   }

   ④getters.js中：定义数据映射

   export const playHistory = state => state.playHistory

2. player.vue中：当歌曲ready后通过mapActions向Vuex中写入数据

   ready() {
      this.songReady = true
      this.savePlayHistory(this.currentSong)
   }
   ...mapActions([
      'savePlayHistory' 
   ])

3. catch.js中：实现对本地缓存的操作

   //将歌曲数据保存到本地缓存
   export function savePlay(song) {
       let songs = storage.get(PLAY_KEY, [])
       insertArray(songs, song, (item) => {
            return item.id === song.id
       }, PLAY_MAX_LENGTH)
       storage.set(PLAY_KEY, songs)
       return songs
   }
   //从本地缓存中取出歌曲数据
   export function loadPlay() {
       return storage.get(PLAY_KEY, [])
   }

4. state.js中：修复playHistory初始值为当前本地缓存中的数据

   playHistory: loadPlay()

5. actions.js中：引入savePlay方法将数据同时存入Vuex和本地缓存

   export const savePlayHistory = function({commit}, song){
       commit(types.SET_PLAY_HISTORY, savePlay(song))
   }

6. add-song.js中：通过mapGetters获取Vuex中的播放历史

   <div class="list-wrapper">
        <scroll class="list-scroll" v-if="currentIndex===0" :data="playHistory">
             <div class="list-inner">
                  <song-list :songs="playHistory"></song-list>
              </div>
        </scroll>
   </div>

   import Scroll from '@/base/scroll/scroll'
   import {mapGetters} from 'vuex'
   import SongList from '@/base/song-list/song-list'
   
   computed: {
       ...mapGetters([
          'playHistory'
      ])
   }

7. add-song.js中：监听select事件，通过mapActionis从播放历史中选择歌曲插入播放列表

   @select="selectSong"

   import Song from '@/common/js/song'
   
   selectSong(song, index) {
      if(index !== 0) {
         //从playHistory中获取到的song还是一个对象，需要实例化为Song类
         this.insertSong(new Song(song))
      }
   },
   ...mapActions([
      'insertSong'
   ])

8. 搜索历史列表：复用SearchList组件以及searchMixin中的数据和方法

   <scroll ref="searchList" class="list-scroll" v-if="currentIndex===1" 
           :data="searchHistory">
          <div class="list-inner">
               <search-list @delete="deleteSearchHistory" @select="addQuery"
                            :searches="searchHistory"></search-list>
          </div>
   </scroll>

9. 优化：在search-list.vue中通过transition-group给删除列表时添加动画
10. 关键：<transition-group>中的元素一定要有key值区分元素间的不同
11. 优化：在添加歌曲到列表页面显示时，判断当前显示列表，对应scroll重新计算，确保高度正确

    show() {
       this.showFlag = true
       setTimeout(() => {
          if(this.currentIndex === 0){
             this.$refs.songList.refresh()
          }else{
             this.$refs.searchList.refresh()
          }
      })
    }

• 顶部提示框

1. base->top-list目录下：创建top-list.vue

   <transition name="drop">
      <div class="top-tip" v-show="showFlag" @click.stop="hide">
           <slot></slot>
      </div> 
   </transition>

   通过showFlag控制显示隐藏，同play-list.vue

2. add-song.vue中：应用top-list，添加slot

   <top-tip ref="topTip">
       <div class="tip-title">
            <i class="icon-ok"></i>
            <span class="text">1首歌曲已经添加到播放队列</span>
       </div>
   </top-tip>

   分别在selectSuggest()和selectSong()中调用showTip()显示提示框

3. top-list.vue中：在show()内调用定时器，设置提示框显示2s自动关闭
4. 坑：如果快速的调用show()，会有很多定时器存在
5. 解决：每次show()时，在调用新的timer前就先清空前面的timer

   props: {
      delay: {
          type: Number,
          default: 2000
      }
   }
   
   show() {
       this.showFlag = true
       clearTimeout(this.timer)
       this.timer = setTimeout(() => {
             this.hide()
        }, this.delay)
   }

五、歌曲列表组件scroll组件能力的扩展

• 坑：添加歌曲到列表后，歌曲播放列表的滚动位置不对了

• 原因：playlist中歌曲列表项的添加了transition-group动画，即添加歌曲后歌曲播放列表的高度需要一个100ms的过程；而外层<scroll :data="sequenceList">在watch到数据的变化后，20ms就重新计算了，计算的高度是不对的

• 解决：扩展scroll组件，添加props属性refreshDelay，让外部组件可以自定义重新计算的延迟时间；扩展后再在外部组件的data中定义refreshDelay：100，最后在<scroll>中传入:refreshDelay="refreshDelay"

  refreshDelay: {
     type: Number,
     default: 20
  }
  
  watch: {
     data() { //监测data的变化
         setTimeout(() => {
             this.refresh()
         }, this.refreshDelay)
     }
  }

• 同上：search-list组件中的列表项也添加了transition-group动画；在引用到的search组件和add-song组件中都需要传入:refreshDelay="refreshDelay"；因为两个组件复用了searchMixin，所以在searchMixin中定义refreshDelay：100

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注：项目来自慕课网