message: fix(Calendar): should update header title
diff: @@ -99,20 +99,27 @@ export default createComponent({
  },
  onScroll() {
  - const scrollTop = getScrollTop(this.$refs.body);
  - const monthsHeight = this.$refs.month.map(item => item.height);
  - const bodyTop = scrollTop;
  - const bodyBottom = scrollTop + this.bodyHeight;
  + const { body, months } = this.$refs;
  + const top = getScrollTop(body);
  + const bottom = top + this.bodyHeight;
  + const heights = months.map(item => item.height);
  +
  let height = 0;
  + let firstMonth;
  +
  + for (let i = 0; i < months.length; i++) {
  + const visible = height <= bottom && height + heights[i] >= top;
  - for (let i = 0; i < this.months.length; i++) {
  - const monthTop = height;
  - const monthBottom = height + monthsHeight[i];
  - const visible = monthTop <= bodyBottom && monthBottom >= bodyTop;
  + if (visible && !firstMonth) {
  + firstMonth = months[i];
  + }
  - this.$refs.month[i].visible = visible;
  + months[i].visible = visible;
  + height += heights[i];
  + }
  - height += monthsHeight[i];
  + if (firstMonth) {
  + this.monthTitle = firstMonth.title;
  }
  },
  @@ -151,7 +158,7 @@ export default createComponent({
  genMonth(date, index) {
  return (
  <Month
  - ref="month"
  + ref="months"
  refInFor
  type={this.type}
  date={date}
  