fix(Tab): set container when change active (#2817)

fix #2782

packages/sticky/index.ts

@@ -30,6 +30,7 @@ VantComponent({
         }
 
         this.observeContainer();
+        this.updateFixed();
       }
     }
   },
@@ -63,6 +64,22 @@ VantComponent({
       );
     },
 
+    updateFixed() {
+      Promise.all([this.getRect(ROOT_ELEMENT), this.getContainerRect()]).then(
+        ([
+          content,
+          container
+        ]: WechatMiniprogram.BoundingClientRectCallbackResult[]) => {
+          this.setData({ height: content.height });
+          this.containerHeight = container.height;
+
+          wx.nextTick(() => {
+            this.setFixed(content.top);
+          });
+        }
+      );
+    },
+
     disconnectObserver(observerName?: string) {
       if (observerName) {
         const observer: WechatMiniprogram.IntersectionObserver = this[

packages/tabs/index.ts

@@ -114,15 +114,19 @@ VantComponent({
   },
 
   mounted() {
-    this.setData({
+    wx.nextTick(() => {
-      container: () => this.createSelectorQuery().select('.van-tabs')
-    }, () => {
       this.setLine(true);
       this.scrollIntoView();
     });
   },
 
   methods: {
+    updateContainer() {
+      this.setData({
+        container: () => this.createSelectorQuery().select('.van-tabs')
+      });
+    },
+
     updateTabs() {
       const { children = [], data } = this;
       this.setData({
@@ -203,6 +207,7 @@ VantComponent({
       wx.nextTick(() => {
         this.setLine();
         this.scrollIntoView();
+        this.updateContainer();
 
         this.trigger('input');
         if (shouldEmitChange) {