vant-weapp/packages/tabs/index.ts

import { VantComponent } from '../common/component';
import { touch } from '../mixins/touch';
import { Weapp } from 'definitions/weapp';
import { nextTick, isDef, addUnit } from '../common/utils';

type TabItemData = {
  width?: number;
  active: boolean;
  inited?: boolean;
  animated?: boolean;
  name?: string | number;
};

VantComponent({
  mixins: [touch],

  classes: ['nav-class', 'tab-class', 'tab-active-class', 'line-class'],

  relation: {
    name: 'tab',
    type: 'descendant',
    linked(child) {
      child.index = this.children.length;
      this.children.push(child);
      this.updateTabs(this.data.tabs.concat(child.data));
    },
    unlinked(child) {
      const index = this.children.indexOf(child);
      const { tabs } = this.data;
      tabs.splice(index, 1);
      this.children.splice(index, 1);

      let i = index;
      while (i >= 0 && i < this.children.length) {
        const currentChild = this.children[i];
        currentChild.index--;
        i++;
      }

      this.updateTabs(tabs);
    }
  },

  props: {
    color: {
      type: String,
      observer: 'setLine'
    },
    sticky: Boolean,
    animated: {
      type: Boolean,
      observer: 'setTrack'
    },
    swipeable: Boolean,
    lineWidth: {
      type: [String, Number],
      value: -1,
      observer: 'setLine'
    },
    lineHeight: {
      type: [String, Number],
      value: -1,
      observer: 'setLine'
    },
    active: {
      type: [String, Number],
      value: 0,
      observer(value) {
        this.currentName = value;
        this.setActiveTab();
      }
    },
    type: {
      type: String,
      value: 'line'
    },
    border: {
      type: Boolean,
      value: true
    },
    duration: {
      type: Number,
      value: 0.3
    },
    zIndex: {
      type: Number,
      value: 1
    },
    swipeThreshold: {
      type: Number,
      value: 4,
      observer() {
        this.setData({
          scrollable: this.children.length > this.data.swipeThreshold
        });
      }
    },
    offsetTop: {
      type: Number,
      value: 0
    }
  },

  data: {
    tabs: [],
    lineStyle: '',
    scrollLeft: 0,
    scrollable: false,
    trackStyle: '',
    wrapStyle: '',
    position: '',
    currentIndex: 0
  },

  beforeCreate() {
    this.children = [];
  },

  mounted() {
    this.setLine(true);
    this.setTrack();
    this.scrollIntoView();
  },

  methods: {
    updateTabs(tabs: TabItemData[]) {
      tabs = tabs || this.data.tabs;
      this.setData({
        tabs,
        scrollable: tabs.length > this.data.swipeThreshold
      });
      this.setActiveTab();
    },

    trigger(eventName: string, name: string | number) {
      const { tabs, currentIndex } = this.data;

      this.$emit(eventName, {
        name,
        title: tabs[currentIndex].title
      });
    },

    onTap(event: Weapp.Event) {
      const { index } = event.currentTarget.dataset;
      const child = this.children[index];
      const computedName = child.getComputedName();

      if (this.data.tabs[index].disabled) {
        this.trigger('disabled', computedName);
      } else {
        this.trigger('click', computedName);
        this.setActive(computedName);
      }
    },

    setActive(name) {
      if (name !== this.currentName) {
        this.currentName = name;
        this.trigger('change', name);
        this.setActiveTab();
      }
    },

    setLine(skipTransition?: boolean) {
      if (this.data.type !== 'line') {
        return;
      }

      const {
        color,
        duration,
        currentIndex,
        lineWidth,
        lineHeight
      } = this.data;

      this.getRect('.van-tab', true).then(
        (rects: WechatMiniprogram.BoundingClientRectCallbackResult[]) => {
          const rect = rects[currentIndex];
          const width = lineWidth !== -1 ? lineWidth : rect.width / 2;
          const height =
            lineHeight !== -1
              ? `height: ${addUnit(lineHeight)}; border-radius: ${addUnit(lineHeight)};`
              : '';

          let left = rects
            .slice(0, currentIndex)
            .reduce((prev, curr) => prev + curr.width, 0);

          left += (rect.width - width) / 2;

          const transition = skipTransition
            ? ''
            : `transition-duration: ${duration}s; -webkit-transition-duration: ${duration}s;`;

          this.setData({
            lineStyle: `
            ${height}
            width: ${addUnit(width)};
            background-color: ${color};
            -webkit-transform: translateX(${left}px);
            transform: translateX(${left}px);
            ${transition}
          `
          });
        }
      );
    },

    setTrack() {
      const { animated, duration, currentIndex } = this.data;

      if (!animated) return '';

      this.getRect('.van-tabs__content').then(
        (rect: WechatMiniprogram.BoundingClientRectCallbackResult) => {
          const { width } = rect;

          this.setData({
            trackStyle: `
              width: ${width * this.children.length}px;
              left: ${-1 * currentIndex * width}px;
              transition: left ${duration}s;
              display: -webkit-box;
              display: flex;
            `
          });

          const data = { width, animated };

          this.children.forEach(
            (item: WechatMiniprogram.Component.TrivialInstance) => {
              item.setData(data);
            }
          );
        }
      );
    },

    setActiveTab() {
      if (!isDef(this.currentName)) {
        const { active } = this.data;
        const { children = [] } = this;

        this.currentName =
          active === '' && children.length
            ? children[0].getComputedName()
            : active;
      }

      this.children.forEach(
        (item: WechatMiniprogram.Component.TrivialInstance, index: number) => {
          const data: TabItemData = {
            active: item.getComputedName() === this.currentName
          };

          if (data.active) {
            this.setData({ currentIndex: index });
            data.inited = true;
          }

          if (data.active !== item.data.active) {
            item.setData(data);
          }
        }
      );

      nextTick(() => {
        this.setLine();
        this.setTrack();
        this.scrollIntoView();
      });
    },

    // scroll active tab into view
    scrollIntoView() {
      const { currentIndex, scrollable } = this.data;

      if (!scrollable) {
        return;
      }

      Promise.all([
        this.getRect('.van-tab', true),
        this.getRect('.van-tabs__nav')
      ]).then(
        ([tabRects, navRect]: [
          WechatMiniprogram.BoundingClientRectCallbackResult[],
          WechatMiniprogram.BoundingClientRectCallbackResult
        ]) => {
          const tabRect = tabRects[currentIndex];
          const offsetLeft = tabRects
            .slice(0, currentIndex)
            .reduce((prev, curr) => prev + curr.width, 0);

          this.setData({
            scrollLeft: offsetLeft - (navRect.width - tabRect.width) / 2
          });
        }
      );
    },

    onTouchStart(event: Weapp.TouchEvent) {
      if (!this.data.swipeable) return;

      this.touchStart(event);
    },

    onTouchMove(event: Weapp.TouchEvent) {
      if (!this.data.swipeable) return;

      this.touchMove(event);
    },

    // watch swipe touch end
    onTouchEnd() {
      if (!this.data.swipeable) return;

      const { tabs, currentIndex } = this.data;

      const { direction, deltaX, offsetX } = this;
      const minSwipeDistance = 50;

      if (direction === 'horizontal' && offsetX >= minSwipeDistance) {
        if (deltaX > 0 && currentIndex !== 0) {
          const child = this.children[currentIndex - 1];
          this.setActive(child.getComputedName());
        } else if (deltaX < 0 && currentIndex !== tabs.length - 1) {
          const child = this.children[currentIndex - 1];
          this.setActive(child.getComputedName());
        }
      }
    }
  }
});