Vue2.0 实现歌手列表滚动及右侧快速入口功能

1 歌手列表

歌手列表页类似于手机通讯录，我们也将其作为一个基础组件独立出来，这部分的逻辑比较简单，这里不做过多的讲解

// base/listview/listview.vue
<template>
  <scroll class="listview" :data="data">
    <ul>
      <li v-for="(group, index) in data" :key="index" class="list-group">
        <h2 class="list-group-title">{{group.title}}</h2>
        <uL>
          <li v-for="(item, index) in group.items" :key="index" class="list-group-item">
            <img class="avatar" v-lazy="item.avatar">
            <span class="name">{{item.name}}</span>
          </li>
        </uL>
      </li>
    </ul>
  </scroll>
</template>
<script type="text/ecmascript-6">
  import Scroll from 'base/scroll/scroll'
  export default {
    props: {
      data: {
        type: Array,
        default: () => []
      }
    },
    components: {
      Scroll
    }
  }
</script>
<style scoped lang="stylus" rel="stylesheet/stylus">
  @import "~common/stylus/variable"
  .listview
    position: relative
    width: 100%
    height: 100%
    overflow: hidden
    background: $color-background
    .list-group
      padding-bottom: 30px
      .list-group-title
        height: 30px
        line-height: 30px
        padding-left: 20px
        font-size: $font-size-small
        color: $color-text-l
        background: $color-highlight-background
      .list-group-item
        display: flex
        align-items: center
        padding: 20px 0 0 30px
        .avatar
          width: 50px
          height: 50px
          border-radius: 50%
        .name
          margin-left: 20px
          color: $color-text-l
          font-size: $font-size-medium
    .list-shortcut
      position: absolute
      z-index: 30
      right: 0
      top: 50%
      transform: translateY(-50%)
      width: 20px
      padding: 20px 0
      border-radius: 10px
      text-align: center
      background: $color-background-d
      font-family: Helvetica
      .item
        padding: 3px
        line-height: 1
        color: $color-text-l
        font-size: $font-size-small
        &.current
          color: $color-theme
          font-weight: bolder
    .list-fixed
      position: absolute
      top: -1px
      left: 0
      width: 100%
      .fixed-title
        height: 30px
        line-height: 30px
        padding-left: 20px
        font-size: $font-size-small
        color: $color-text-l
        background: $color-highlight-background
    .loading-container
      position: absolute
      width: 100%
      top: 50%
      transform: translateY(-50%)
</style>
// singer.vue
<template>
 <div class="singer">
  <list-view :data="singerList"></list-view>
 </div>
</template>
<script type="text/ecmascript-6">
 import ListView from 'base/listview/listview'
 export default {
  ...
  components: {
   ListView
  }
 }
</script>

运行结果

2 右侧快速入口_点击滚动

同样是类比于手机通讯录，悬浮于屏幕右侧的 A-Z 可以帮助我们快速找到对应的歌手，为此，我们需要获取 title 的集合数组

// listview.vue
<div class="list-shortcut">
  <ul>
    <li v-for="(item, index) in shortcutList" :key="index" class="item">{{item}}</li>
  </ul>
</div>
<script type="text/ecmascript-6">
  export default {
    ...
    computed: {
      shortcutList() {
        return this.data.map((group) => {
          return group.title.substr(0, 1)
        })
      }
    }
  }
</script>

运行结果

快速入口出现了之后，我们接下来就为其添加点击事件，当我们点击对应字母时，需要获取其索引，这里我们直接获取 v-for 提供的 index 即可

// listview.vue
<ul>
  <li v-for="(item, index) in shortcutList" :key="index" @touchstart="onShortcutTouchStart($even, index)" class="item">{{item}}</li>
</ul>
export default {
  ...
  methods: {
    onShortcutTouchStart(e, index) {
      console.log(index)
    }
  }
}

点击之后，我们需要页面滚动到相应位置，这里需要扩展 scroll 组件的方法，这里扩展的方法都是来自 better-scroll 组件所封装的方法，这里提一下 scrollToElement 方法的第二个参数是动画时间，可根据自身需求进行设置

// scroll.vue
methods: {
 ...
 scrollTo() {
  this.scroll && this.scroll.scrollTo.apply(this.scroll, arguments)
 },
 scrollToElement() {
  this.scroll && this.scroll.scrollToElement.apply(this.scroll, arguments)
 }
}

随后给 scroll 组件添加 ref="listview" 以及歌手列表添加 ref="listGroup" 方便我们调用

// listview.vue
export default {
  ...
  methods: {
    onShortcutTouchStart(e, index) {
      this.$refs.listview.scrollToElement(this.$refs.listGroup[index], 0)
    }
  }
}

运行结果

3 右侧快速入口_滑动滚动

当我们的手指在右侧快速入口上滑动时，歌手列表也会同步进行滚动，当我们滚动右侧快速入口时，我们需要阻止歌手列表滚动，以及浏览器原生滚动，所以要使用 @touchmove.stop.prevent 阻止冒泡，并且在 onShortcutTouchStart 事件中记录触碰点的初始位置，以及 onShortcutTouchMove 事件中触碰点的位置，通过两个位置的像素差，来滚动歌手列表

// listview.vue
<div class="list-shortcut" @touchmove.stop.prevent="onShortcutTouchMove">
  <ul>
    <li v-for="(item, index) in shortcutList" :key="index" @touchstart="onShortcutTouchStart($event, index)" class="item">{{item}}</li>
  </ul>
</div>
<script type="text/ecmascript-6">
  const ANCHOR_HEIGHT = 18
  export default {
    created() {
      this.touch = {}
    },
    ...
    methods: {
      onShortcutTouchStart(e, index) {
        let firstTouch = e.touches[0]
        this.touch.y1 = firstTouch.pageY
        this.touch.anchorIndex = index
        this._scrollTo(index)
      },
      onShortcutTouchMove(e) {
        let firstTouch = e.touches[0]
        this.touch.y2 = firstTouch.pageY
        let delta = (this.touch.y2 - this.touch.y1) / ANCHOR_HEIGHT | 0
        let anchorIndex = this.touch.anchorIndex + delta
        this._scrollTo(anchorIndex)
      },
      _scrollTo(index) {
        this.$refs.listview.scrollToElement(this.$refs.listGroup[index], 0)
      }
    },
    components: {
      Scroll
    }
  }
</script>

运行结果

4 右侧快速入口_高亮设置

当歌手列表滚动时，我们想要在右侧快速入口中，高亮当前显示的 title ，这就需要我们监听 scroll 组件的滚动事件，来获取当前滚动的位置

// scroll.vue
<script type="text/ecmascript-6">
 export default {
  props: {
   ...
   listenScroll: {
    type: Boolean,
    default: false
   }
  },
  methods: {
   _initScroll() {
    ...
    if (this.listenScroll) {
     let me = this
     this.scroll.on('scroll', (pos) => {
      me.$emit('scroll', pos)
     })
    }
   }
  }
 }
</script>

我们当初给参数 probeType 设的默认值为 1，即会非实时（屏幕滑动超过一定时间后）派发 scroll 事件，我们在屏幕滑动的过程中，需要实时派发 scroll 事件，所以在 listview 中将 probeType 的值设为 3

// listview.vue
<template>
    <scroll class="listview"
            :data="data"
            ref="listview"
            :probe-type="probeType"
            :listenScroll="listenScroll"
            @scroll="scroll">
        <ul>
            ...
        </ul>
        <div class="list-shortcut" @touchmove.stop.prevent="onShortcutTouchMove">
            <ul>
                <li v-for="(item, index) in shortcutList"
                    :key="index"
                    :class="{'current':currentIndex===index}"
                    @touchstart="onShortcutTouchStart($event, index)"
                    class="item">{{item}}</li>
            </ul>
        </div>
    </scroll>
</template>
<script type="text/ecmascript-6">
    export default {
        created() {
            ...
            this.listHeight = []
            this.probeType = 3
        },
        data() {
            return {
                scrollY: -1,
                currentIndex: 0
            }
        },
        methods: {
            ...
            scroll(pos) {
                this.scrollY = pos.y
            },
            _scrollTo(index) {
                this.scrollY = -this.listHeight[index]
                this.$refs.listview.scrollToElement(this.$refs.listGroup[index], 0)
            },
            _calculateHeight() {
                this.listHeight = []
                const list = this.$refs.listGroup
                let height = 0
                this.listHeight.push(height)
                for (let i = 0; i < list.length; i++) {
                    let item = list[i]
                    height += item.clientHeight
                    this.listHeight.push(height)
                }
            }
        },
        watch: {
            data() {
                this.$nextTick(() => {
                    this._calculateHeight()
                })
            },
             scrollY(newY) {
                const listHeight = this.listHeight
                // 当滚动到顶部，newY>0
                if (newY > 0) {
                    this.currentIndex = 0
                    return
                }
                // 在中间部分滚动
                for (let i = 0; i < listHeight.length - 1; i++) {
                    let height1 = listHeight[i]
                    let height2 = listHeight[i + 1]
                    if (-newY >= height1 && -newY < height2) {
                        this.currentIndex = i
                        return
                    }
                }
                // 当滚动到底部，且-newY大于最后一个元素的上限
                this.currentIndex = listHeight.length - 2
            }
        },
        components: {
            Scroll
        }
    }
</script>

运行结果

5 滚动固定标题

当我们滚动歌手列表页时，希望该歌手的 title 一直显示在顶部，并且滚动到下一个 title 时，新的 title 将旧的 title 顶替掉，这里就需要我们计算一个 title 的高度

// listview.vue
<template>
    <scroll class="listview"
            :data="data"
            ref="listview"
            :probe-type="probeType"
            :listenScroll="listenScroll"
            @scroll="scroll">
        ...
        <div class="list-fixed" ref="fixed" v-show="fixedTitle">
            <div class="fixed-title">{{fixedTitle}}</div>
        </div>
    </scroll>
</template>
<script type="text/ecmascript-6">
    import Scroll from 'base/scroll/scroll'
    const TITLE_HEIGHT = 28
    const ANCHOR_HEIGHT = 18
    export default {
        ...
        data() {
            return {
                scrollY: -1,
                currentIndex: 0,
                diff: -1
            }
        },
        computed: {
            ...
            fixedTitle() {
                if (this.scrollY > 0) {
                    return ''
                }
                return this.data[this.currentIndex] ? this.data[this.currentIndex].title : ''
            }
        },
        watch: {
            ...
            scrollY(newY) {
                ...
                for (let i = 0; i < listHeight.length - 1; i++) {
                    ...
                    if (-newY >= height1 && -newY < height2) {
                        ...
                        this.diff = height2 + newY
                        return
                    }
                }
                ...
            },
            diff(newVal) {
                let fixedTop = (newVal > 0 && newVal < TITLE_HEIGHT) ? newVal - TITLE_HEIGHT : 0
                if (this.fixedTop === fixedTop) {
                    return
                }
                this.fixedTop = fixedTop
                this.$refs.fixed.style.transform = `translate3d(0,${fixedTop}px,0)`
            }
        }
    }
</script>

运行结果

该章节的内容到这里就全部结束了，源码我已经发到了 GitHub Vue_Music_06 上了，有需要的同学可自行下载

总结