Press n or j to go to the next uncovered block, b, p or k for the previous block.
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import FVirtualList from '../f-virtual-list.vue';
export default {
name: 'f-virtual-table',
extends: FVirtualList,
computed: {
virtualList() {
const list = this[this.listKey];
if (!this.virtual)
return list;
else {
let count = 0;
for (let i = this.virtualIndex; i < list.length; i++) {
const item = list[i];
if (item.display !== 'none') {
count++;
}
if (count >= this.virtualCount || i === list.length - 1) {
return list.slice(this.virtualIndex, i + 1);
}
}
return [];
}
},
},
methods: {
handleVirtualScroll(e) {
if (!this.virtual)
return;
const listEl = e.target;
let virtualEl = this.$refs.virtual;
if (Array.isArray(virtualEl)) {
virtualEl = virtualEl[0];
}
let tablebodyEl = this.$refs.body;
if (Array.isArray(tablebodyEl)) {
tablebodyEl = tablebodyEl[0];
}
const list = this[this.listKey];
const showList = (list || []).filter((item) => item.display !== 'none');
if (!virtualEl || !list)
return; // 缓存当前可见 DOM 节点的高度
if (this.itemHeight === undefined) {
const children = Array.from(virtualEl.children);
children.forEach((childEl, index) => {
const item = list[this.virtualIndex + index];
if (
item
&& item.height === undefined
&& item._cacheHeight === undefined
)
item._cacheHeight = item.height || childEl.offsetHeight;
});
}
const getHeight = (item) => {
if (item.display === 'none')
return 0;
else if (this.itemHeight !== undefined)
return this.itemHeight;
else if (item.height !== undefined)
return item.height;
else if (item._cacheHeight !== undefined)
return item._cacheHeight;
else
return 0;
};
const scrollTop = listEl.scrollTop;
let accHeight = 0;
let virtualIndex = this.virtualIndex;
let currentIndex = 0;
for (currentIndex = 0; currentIndex < list.length; currentIndex++) {
const item = list[currentIndex];
if (accHeight > scrollTop)
break;
accHeight += getHeight(item);
}
let showCount = 0;
if (getHeight(list[0])) {
showCount = Math.ceil(tablebodyEl.clientHeight / getHeight(list[0]));
}
virtualIndex = Math.max(
0,
currentIndex - Math.ceil((this.virtualCount - showCount) / 2),
); // eslint-disable-next-line yoda
// table 树形展示里不能这么处理，暂时注释掉
// 该方法容易出现白屏。有截流了问题不大。
// if (
// this.virtualCount / 3 <= currentIndex - this.virtualIndex
// && currentIndex - this.virtualIndex < (this.virtualCount * 2) / 3
// )
// return;
let virtualTop = 0;
let virtualBottom = 0;
let noDisplayCount = 0;
for (let i = 0; i < list.length; i++) {
const item = list[i];
if (i < virtualIndex) {
virtualTop += getHeight(item);
} else if (i >= virtualIndex + this.virtualCount) {
virtualBottom += getHeight(item);
}
if (i > virtualIndex && i <= virtualIndex + this.virtualCount) {
if (item.display === 'none') {
noDisplayCount++;
}
}
}
this.virtualIndex = virtualIndex;
this.virtualTop = virtualTop;
this.virtualBottom = virtualBottom; // Vue 应该是对渲染做了优化，为了减少在高频滚动时出现白屏的问题，需要强制更新
this.$nextTick(() => {
this.$forceUpdate();
this.$emit(
'virtual-scroll',
{
virtualIndex,
virtualCount: this.virtualCount,
virtualTop,
virtualBottom,
},
this,
);
});
},
},
};
</script>
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