vant-weapp/packages/tree-select/index.ts

import { VantComponent } from '../common/component';
import { Weapp } from 'definitions/weapp';

const ITEM_HEIGHT = 44;

VantComponent({
  classes: [
    'main-item-class',
    'content-item-class',
    'main-active-class',
    'content-active-class',
    'main-disabled-class',
    'content-disabled-class'
  ],

  props: {
    items: Array,
    mainActiveIndex: {
      type: Number,
      value: 0
    },
    activeId: {
      type: [Number, String]
    },
    maxHeight: {
      type: Number,
      value: 300
    }
  },

  data: {
    subItems: [],
    mainHeight: 0,
    itemHeight: 0
  },

  watch: {
    items() {
      this.updateSubItems().then(() => {
        this.updateMainHeight();
      });
    },

    maxHeight() {
      this.updateItemHeight(this.data.subItems);
      this.updateMainHeight();
    },

    mainActiveIndex: 'updateSubItems'
  },

  methods: {
    // 当一个子项被选择时
    onSelectItem(event: Weapp.Event) {
      const { item } = event.currentTarget.dataset;
      if (!item.disabled) {
        this.$emit('click-item', item);
      }
    },

    // 当一个导航被点击时
    onClickNav(event: Weapp.Event) {
      const { index } = event.currentTarget.dataset;
      const item = this.data.items[index];
      if (!item.disabled) {
        this.$emit('click-nav', { index });
      }
    },

    // 更新子项列表
    updateSubItems() {
      const { items, mainActiveIndex } = this.data;
      const { children = [] } = items[mainActiveIndex] || {};

      this.updateItemHeight(children);
      return this.set({ subItems: children });
    },

    // 更新组件整体高度，根据最大高度和当前组件需要展示的高度来决定
    updateMainHeight() {
      const { items = [], subItems = [] } = this.data;
      const maxHeight = Math.max(
        items.length * ITEM_HEIGHT,
        subItems.length * ITEM_HEIGHT
      );

      this.set({ mainHeight: Math.min(maxHeight, this.data.maxHeight) });
    },

    // 更新子项列表高度，根据可展示的最大高度和当前子项列表的高度决定
    updateItemHeight(subItems) {
      const itemHeight = Math.min(subItems.length * ITEM_HEIGHT, this.data.maxHeight);

      return this.set({ itemHeight });
    }
  }
});