447 lines
15 KiB
Vue
447 lines
15 KiB
Vue
<template>
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<view
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:style="tools._style([customStyle, 'height:' + itemHeight * visibleItemCount + 'px'])"
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:class="tools.cls(classPrefix + '__group', []) + ' ' + tClass"
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@touchstart="onTouchStart"
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@touchmove.stop.prevent="onTouchMove"
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@touchend="onTouchEnd"
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@touchcancel="onTouchEnd"
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>
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<view
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:class="classPrefix + '__wrapper'"
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:style="
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'transition: transform ' + duration + 'ms cubic-bezier(0.215, 0.61, 0.355, 1); transform: translate3d(0, ' + offset + 'px, 0); padding: ' + wrapperPaddingY + 'px 0'
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"
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>
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<!-- 虚拟滚动：占位容器（撑开总高度） -->
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<view
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v-if="enableVirtualScroll"
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:style="'height: ' + totalHeight + 'px; position: relative;'"
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>
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<!-- 可见区域（绝对定位） -->
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<view :style="'position: absolute; top: ' + virtualOffsetY + 'px; left: 0; right: 0;'">
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<view
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v-for="(option, index) in visibleOptions"
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:key="index"
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:class="tools.cls(classPrefix + '__item', [['active', curIndex == virtualStartIndex + index]])"
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:style="'height: ' + itemHeight + 'px'"
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:data-index="virtualStartIndex + index"
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@tap="onClickItem"
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>
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<t-icon
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v-if="option[keys.icon]"
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:class="classPrefix + '__item-icon'"
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:name="option[keys.icon]"
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/>
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<text :class="classPrefix + '__item-label'">
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{{ option[keys.label] }}
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</text>
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<slot
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v-if="useSlots"
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:name="'label-suffix--' + (virtualStartIndex + index)"
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/>
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</view>
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</view>
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</view>
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<!-- 非虚拟滚动：原有实现 -->
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<template v-else>
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<view
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v-for="(option, index) in visibleOptions"
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:key="index"
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:class="tools.cls(classPrefix + '__item', [['active', curIndex == index]])"
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:style="'height: ' + itemHeight + 'px'"
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:data-index="index"
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@click="onClickItem"
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>
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<t-icon
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v-if="option[keys.icon]"
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:class="classPrefix + '__item-icon'"
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:name="option[keys.icon]"
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/>
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<text :class="classPrefix + '__item-label'">
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{{ option[keys.label] }}
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</text>
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<slot
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v-if="useSlots"
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:name="'label-suffix--' + index"
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/>
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</view>
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</template>
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</view>
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</view>
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</template>
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<script>
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import TIcon from '../icon/icon.vue';
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import { uniComponent } from '../common/src/index';
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import { prefix } from '../common/config';
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import props from './props';
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import tools from '../common/utils.wxs';
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import { nextTick } from '../common/utils';
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import { ChildrenMixin, RELATION_MAP } from '../common/relation';
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const name = `${prefix}-picker-item`;
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// 动画持续时间（优化：根据滑动距离动态计算，基础时长降低）
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const ANIMATION_DURATION_BASE = 300; // 基础动画时长
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const ANIMATION_DURATION_MAX = 600; // 最大动画时长
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// 和上一次move事件间隔小于INERTIA_TIME
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const INERTIA_TIME = 300;
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// 且距离大于`MOMENTUM_DISTANCE`时，执行惯性滚动
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const INERTIA_DISTANCE = 15;
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// 虚拟滚动配置
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const VIRTUAL_SCROLL_CONFIG = {
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ENABLE_THRESHOLD: 100, // 超过100个选项启用虚拟滚动
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// VISIBLE_COUNT: 5, // 可见区域显示5个选项，使用 visibleItemCount 属性代替
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BUFFER_COUNT: 8, // 上下各缓冲8个选项（增加缓冲区，防止快速滑动时空白）
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THROTTLE_TIME: 16, // 节流时间（60fps，提高更新频率）
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FAST_SCROLL_BUFFER: 12, // 快速滑动时的额外缓冲区
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FAST_SCROLL_THRESHOLD: 50, // 判定为快速滑动的速度阈值（px/frame）
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};
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const range = function (num, min, max) {
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return Math.min(Math.max(num, min), max);
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};
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const momentum = (distance, duration) => {
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let nDistance = distance;
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// 惯性滚动的速度
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const speed = Math.abs(nDistance / duration);
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// 加速度经验值: 0.005
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// 惯性滚动的距离
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nDistance = (speed / 0.005) * (nDistance < 0 ? -1 : 1);
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return nDistance;
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};
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export default uniComponent({
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name,
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components: {
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TIcon,
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},
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options: {
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styleIsolation: 'shared',
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virtualHost: true,
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},
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externalClasses: [
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`${prefix}-class`,
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],
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mixins: [
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ChildrenMixin(RELATION_MAP.PickerItem),
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],
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props: {
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...props,
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useSlots: {
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type: Boolean,
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value: true,
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},
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},
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data() {
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return {
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prefix,
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classPrefix: name,
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offset: 0, // 滚动偏移量
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duration: 0, // 滚动动画延迟
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value: '',
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curIndex: 0,
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columnIndex: 0,
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keys: {},
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formatOptions: props.options.value,
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tools,
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enableVirtualScroll: false,
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visibleOptions: [],
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virtualStartIndex: 0,
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virtualOffsetY: 0,
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totalHeight: 0,
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itemHeight: 40,
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visibleItemCount: 5,
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wrapperPaddingY: 72,
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};
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},
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watch: {
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options: {
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handler() {
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this.update();
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},
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immediate: true,
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},
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keys: {
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handler() {
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this.update();
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},
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immediate: true,
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},
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},
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created() {
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this.StartY = 0;
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this.StartOffset = 0;
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this.startTime = 0;
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this._animationTimer = null; // 动画期间更新虚拟滚动的定时器
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},
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mounted() {
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},
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beforeUnMount() {
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// 清理定时器，防止内存泄漏
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if (this._animationTimer) {
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clearInterval(this._animationTimer);
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this._animationTimer = null;
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}
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},
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methods: {
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onClickItem(event) {
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const { index: clickIndex } = event.currentTarget.dataset;
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const { itemHeight } = this;
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const index = range(clickIndex, 0, this.getCount() - 1);
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if (index !== this._selectedIndex) {
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this.offset = -index * itemHeight;
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this.curIndex = index;
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this.duration = 200;
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}
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this.updateSelected(index, true);
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},
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onTouchStart(event) {
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this.StartY = event.touches[0].clientY;
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this.StartOffset = this.offset;
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this.startTime = Date.now();
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this.duration = 0;
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},
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onTouchMove(event) {
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const { StartY, StartOffset } = this;
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const { itemHeight } = this;
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// 偏移增量
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const deltaY = event.touches[0].clientY - StartY;
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const newOffset = range(StartOffset + deltaY, -(this.getCount() - 1) * itemHeight, 0);
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// touchMove 期间只更新 offset，不更新虚拟滚动数据
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// 虚拟滚动数据在 touchEnd 时统一更新，避免频繁 setData 导致掉帧
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this.offset = newOffset;
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},
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onTouchEnd(event) {
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const { offset, itemHeight, enableVirtualScroll, formatOptions } = this;
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const { startTime } = this;
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if (offset === this.StartOffset) {
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return;
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}
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// 判断是否需要惯性滚动
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let distance = 0;
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const move = event.changedTouches[0].clientY - this.StartY;
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const moveTime = Date.now() - startTime;
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if (moveTime < INERTIA_TIME && Math.abs(move) > INERTIA_DISTANCE) {
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distance = momentum(move, moveTime);
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}
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// 调整偏移量
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const newOffset = range(offset + distance, -this.getCount() * itemHeight, 0);
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const index = range(Math.round(-newOffset / itemHeight), 0, this.getCount() - 1);
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const finalOffset = -index * itemHeight;
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// 动态计算动画时长：根据滑动距离调整，距离越大时长越长，但有上限
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const scrollDistance = Math.abs(finalOffset - offset);
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const scrollItems = scrollDistance / itemHeight;
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const animationDuration = Math.min(
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ANIMATION_DURATION_MAX,
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ANIMATION_DURATION_BASE + scrollItems * 30, // 每滑动一个选项增加30ms
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);
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// 判断是否为快速惯性滚动（用于决定缓冲区大小）
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const isFastInertia = Math.abs(distance) > itemHeight * 3;
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// 根据是否快速惯性滚动选择缓冲区大小
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const bufferCount = isFastInertia ? VIRTUAL_SCROLL_CONFIG.FAST_SCROLL_BUFFER : VIRTUAL_SCROLL_CONFIG.BUFFER_COUNT;
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// 清除之前的动画更新定时器
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if (this._animationTimer) {
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clearInterval(this._animationTimer);
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this._animationTimer = null;
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}
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// 性能优化：直接赋值更新所有状态
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this.offset = finalOffset;
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this.duration = animationDuration;
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this.curIndex = index;
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// 虚拟滚动：预先计算覆盖动画全程的可见范围，避免动画期间频繁更新
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if (enableVirtualScroll) {
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// 计算当前位置和目标位置的索引范围
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const currentIndex = Math.floor(Math.abs(offset) / itemHeight);
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const targetIndex = index;
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// 计算覆盖动画全程的可见范围（从当前位置到目标位置）
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const minIndex = Math.min(currentIndex, targetIndex);
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const maxIndex = Math.max(currentIndex, targetIndex);
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// 使用缓冲区扩展范围，确保动画过程中不会出现空白
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const animationStartIndex = Math.max(0, minIndex - bufferCount);
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const animationEndIndex = Math.min(formatOptions.length, maxIndex + this.visibleItemCount + bufferCount);
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this.visibleOptions = formatOptions.slice(animationStartIndex, animationEndIndex);
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this.virtualStartIndex = animationStartIndex;
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this.virtualOffsetY = animationStartIndex * itemHeight;
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// 使用 nextTick 确保 DOM 更新后再执行后续操作
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nextTick().then(() => {
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// 动画结束后，精确更新虚拟滚动视图到最终位置
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const visibleRange = this.computeVirtualRange(finalOffset, formatOptions.length, itemHeight, false);
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this.visibleOptions = formatOptions.slice(visibleRange.startIndex, visibleRange.endIndex);
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this.virtualStartIndex = visibleRange.startIndex;
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this.virtualOffsetY = visibleRange.startIndex * itemHeight;
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});
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}
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if (index === this._selectedIndex) return;
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this.updateSelected(index, true);
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},
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formatOption(options, columnIndex, format) {
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if (typeof format !== 'function') return options;
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return options.map(ele => format(ele, columnIndex));
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},
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updateSelected(index, trigger) {
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const { columnIndex, keys, formatOptions } = this;
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this._selectedIndex = index;
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this._selectedValue = formatOptions[index]?.[keys?.value];
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this._selectedLabel = formatOptions[index]?.[keys?.label];
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if (trigger) {
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this[RELATION_MAP.PickerItem]?.triggerColumnChange({
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index,
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column: columnIndex,
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});
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}
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},
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// 刷新选中状态
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update() {
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const { options, value, keys, format, columnIndex, itemHeight, visibleItemCount } = this;
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const formatOptions = this.formatOption(options, columnIndex, format);
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const optionsCount = formatOptions.length;
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// 判断是否启用虚拟滚动
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const enableVirtualScroll = optionsCount >= VIRTUAL_SCROLL_CONFIG.ENABLE_THRESHOLD;
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// 大数据量优化：使用 Map 快速查找索引
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let index = -1;
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if (optionsCount > 500) {
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// 构建临时 Map（只在查找时构建，不缓存）
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const valueMap = new Map(formatOptions.map((item, idx) => [item[keys?.value], idx]));
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index = valueMap.get(value) ?? -1;
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} else {
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index = formatOptions.findIndex(item => item[keys?.value] === value);
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}
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const selectedIndex = index > 0 ? index : 0;
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// 计算wrapper的padding，确保选中项居中显示
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const wrapperPaddingY = ((visibleItemCount - 1) / 2) * itemHeight;
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// 直接赋值更新所有状态
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this.formatOptions = formatOptions;
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this.offset = -selectedIndex * itemHeight;
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this.curIndex = selectedIndex;
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this.enableVirtualScroll = enableVirtualScroll;
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this.totalHeight = optionsCount * itemHeight;
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this.wrapperPaddingY = wrapperPaddingY;
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// 如果启用虚拟滚动，计算可见选项
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if (enableVirtualScroll) {
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const visibleRange = this.computeVirtualRange(-selectedIndex * itemHeight, optionsCount, itemHeight);
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this.visibleOptions = formatOptions.slice(visibleRange.startIndex, visibleRange.endIndex);
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this.virtualStartIndex = visibleRange.startIndex;
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this.virtualOffsetY = visibleRange.startIndex * itemHeight;
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} else {
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// 不启用虚拟滚动时，visibleOptions 等于 formatOptions
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this.visibleOptions = formatOptions;
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this.virtualStartIndex = 0;
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this.virtualOffsetY = 0;
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}
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nextTick().then(() => {
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this.updateSelected(selectedIndex, false);
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});
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},
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/**
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* 计算虚拟滚动的可见范围
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* @param offset 当前滚动偏移量
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* @param totalCount 总选项数量
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* @param itemHeight 单个选项高度
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* @param isFastScroll 是否为快速滑动
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*/
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computeVirtualRange(offset, totalCount, itemHeight, isFastScroll = false) {
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const scrollTop = Math.abs(offset);
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const { BUFFER_COUNT, FAST_SCROLL_BUFFER } = VIRTUAL_SCROLL_CONFIG;
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const { visibleItemCount } = this;
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// 根据滑动速度动态调整缓冲区大小
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const bufferCount = isFastScroll ? FAST_SCROLL_BUFFER : BUFFER_COUNT;
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// 计算当前可见区域的中心索引
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const centerIndex = Math.floor(scrollTop / itemHeight);
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// 计算起始索引（减去缓冲区）
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const startIndex = Math.max(0, centerIndex - bufferCount);
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// 计算结束索引（加上可见数量和缓冲区）
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const endIndex = Math.min(totalCount, centerIndex + visibleItemCount + bufferCount);
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return { startIndex, endIndex };
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},
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/**
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* 更新虚拟滚动的可见选项
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* @param offset 当前滚动偏移量（可选，不传则使用 data.offset）
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* @param isFastScroll 是否为快速滑动
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*/
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updateVisibleOptions(offset, isFastScroll = false) {
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const { formatOptions, itemHeight, enableVirtualScroll } = this;
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if (!enableVirtualScroll) return;
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const currentOffset = offset !== undefined ? offset : this.offset;
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const visibleRange = this.computeVirtualRange(currentOffset, formatOptions.length, itemHeight, isFastScroll);
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// 只有当可见范围发生变化时才更新
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if (
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visibleRange.startIndex !== this.virtualStartIndex
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|| visibleRange.endIndex !== this.virtualStartIndex + this.visibleOptions.length
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) {
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this.visibleOptions = formatOptions.slice(visibleRange.startIndex, visibleRange.endIndex);
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this.virtualStartIndex = visibleRange.startIndex;
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this.virtualOffsetY = visibleRange.startIndex * itemHeight;
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}
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},
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getCount() {
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return this.options?.length;
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},
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getCurrentSelected() {
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const { offset, itemHeight, formatOptions, keys } = this;
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const currentIndex = Math.max(0, Math.min(Math.round(-offset / itemHeight), this.getCount() - 1));
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return {
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index: currentIndex,
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value: formatOptions[currentIndex]?.[keys?.value],
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label: formatOptions[currentIndex]?.[keys?.label],
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};
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},
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},
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});
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</script>
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<style scoped>
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@import './picker-item.css';
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</style>
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