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