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<template>
<view class="virtual-list" style="position: relative;">
<movable-area style="position: absolute;right: 0;width: 30px;height: 100%;">
<movable-view class="action-bar-box" direction="vertical" @change="change" :y="y" :animation="false">
<view style="border-bottom: #000 solid 2px;width: 100%;"></view>
<view style="border-bottom: #000 solid 2px;width: 100%;"></view>
</movable-view>
</movable-area>
<scroll-view scroll-y="true"
:style="{
'height': scrollHeight + 'px',
'position': 'relative',
'zIndex': 1
}"
@scroll="handleScroll" :scroll-top="scrollTop" :show-scrollbar="false">
<view class="scroll-bar"
:style="{
'height': localHeight + 'px'
}"></view>
<view class="list"
:style="{
'transform': `translateY(${offset}px)`
}">
<view class="item-wrap"
v-for="(item, index) in visibleData"
:key="index">
<slot :item="item" :active="active"></slot>
</view>
</view>
</scroll-view>
</view>
</template>
<script>
export default {
name: 'VirtualList',
props: {
// 所有的items
items: Array,
// 可视区域的item数量
remain: Number,
// item大小
size: Number,
// 当前章节
active: Number,
// 可使区域高度
scrollHeight: Number
},
data() {
return {
// 起始
start: 0,
// 结束
end: this.remain,
// list 偏移量
offset: 0,
scrollTop: 0,
y: 0
}
},
created() {
//当前章节滚动至顶部
this.scrollTop = this.size * this.active
},
computed: {
// 预留项
preCount() {
return Math.min(this.start, this.remain);
},
nextCount() {
return Math.min(this.items.length - this.end, this.remain);
},
// 可视区域的item
visibleData() {
const start = this.start - this.preCount;
const end = this.end + this.nextCount;
console.log(this.items,'this.items.slice(start, end)');
return this.items.slice(start, end);
},
localHeight() {
return this.items.length * this.size
}
},
methods: {
change(e) {
if (e.detail.source !== 'touch') {
return
}
let y = e.detail.y;
let scroll = y/(this.scrollHeight-40)*(this.localHeight-this.scrollHeight);
scroll = scroll < 0 ? 0 : scroll;
this.scrollTop = scroll;
},
handleScroll(ev) {
const scrollTop = ev.detail.scrollTop;
this.y = scrollTop/(this.localHeight-this.scrollHeight)*(this.scrollHeight-40)
// 开始位置
const start = Math.floor(scrollTop / this.size)
this.start = start < 0 ? 0 : start;
// 结束位置
this.end = this.start + this.remain;
// 计算偏移
const offset = scrollTop - (scrollTop % this.size) - this.preCount * this.size
this.offset = offset < 0 ? 0 : offset;
}
}
}
</script>
<style scoped>
.list {
position: absolute;
top: 0;
left: 0;
width: 100%;
}
.action-bar-box{
padding: 3px;
display: flex;
flex-flow: column;
justify-content: space-around;
align-items: center;
position: absolute;
right: 0;
background-color: transparent;
border-radius: 10rpx;
box-shadow: 0 0 5px #000;
width: 20px;
height: 40px;
z-index:2;
}
</style>