fix(IndexBar): fix the problem of rolling out parent boundaries when sucking bottom (#4218)

src/index-anchor/index.js

@@ -14,7 +14,8 @@ export default createComponent({
   data() {
     return {
       top: 0,
-      active: false
+      active: false,
+      position: 'static'
     };
   },
 
@@ -26,9 +27,10 @@ export default createComponent({
     anchorStyle() {
       if (this.sticky) {
         return {
+          position: this.position,
+          zIndex: `${this.parent.zIndex}`,
           transform: `translate3d(0, ${this.top}px, 0)`,
           color: this.parent.highlightColor,
-          zIndex: `${this.parent.zIndex}`
         };
       }
     }

src/index-bar/index.js

@@ -96,16 +96,28 @@ export default createComponent({
       this.activeAnchorIndex = this.indexList[active];
 
       if (this.sticky) {
+        let activeItemTop = 0;
+        let isReachEdge = false;
+
+        if (active !== -1) {
+          activeItemTop = rects[active].top - scrollTop;
+          isReachEdge = activeItemTop <= 0;
+        }
+
         this.children.forEach((item, index) => {
           if (index === active) {
             item.active = true;
-            item.top = Math.max(this.stickyOffsetTop, rects[index].top - scrollTop) + scrollerRect.top;
+            item.position = isReachEdge ? 'fixed' : 'relative';
+            item.top = isReachEdge
+              ? this.stickyOffsetTop + scrollerRect.top
+              : 0;
           } else if (index === active - 1) {
-            const activeItemTop = rects[active].top - scrollTop;
+            item.active = !isReachEdge;
-            item.active = activeItemTop > 0;
+            item.position = 'relative';
-            item.top = activeItemTop + scrollerRect.top - item.height;
+            item.top = item.$el.parentElement.offsetHeight - item.height;
           } else {
             item.active = false;
+            item.position = 'static';
           }
         });
       }

src/index-bar/test/__snapshots__/index.spec.js.snap

@@ -34,10 +34,10 @@ exports[`scroll and update active anchor 2`] = `
 <div class="van-index-bar">
   <div class="van-index-bar__sidebar" style="z-index: 2;"><span data-index="A" class="van-index-bar__index">A</span><span data-index="B" class="van-index-bar__index van-index-bar__index--active" style="color: rgb(7, 193, 96);">B</span><span data-index="C" class="van-index-bar__index">C</span><span data-index="D" class="van-index-bar__index">D</span><span data-index="E" class="van-index-bar__index">E</span><span data-index="F" class="van-index-bar__index">F</span><span data-index="G" class="van-index-bar__index">G</span><span data-index="H" class="van-index-bar__index">H</span><span data-index="I" class="van-index-bar__index">I</span><span data-index="J" class="van-index-bar__index">J</span><span data-index="K" class="van-index-bar__index">K</span><span data-index="L" class="van-index-bar__index">L</span><span data-index="M" class="van-index-bar__index">M</span><span data-index="N" class="van-index-bar__index">N</span><span data-index="O" class="van-index-bar__index">O</span><span data-index="P" class="van-index-bar__index">P</span><span data-index="Q" class="van-index-bar__index">Q</span><span data-index="R" class="van-index-bar__index">R</span><span data-index="S" class="van-index-bar__index">S</span><span data-index="T" class="van-index-bar__index">T</span><span data-index="U" class="van-index-bar__index">U</span><span data-index="V" class="van-index-bar__index">V</span><span data-index="W" class="van-index-bar__index">W</span><span data-index="X" class="van-index-bar__index">X</span><span data-index="Y" class="van-index-bar__index">Y</span><span data-index="Z" class="van-index-bar__index">Z</span></div>
   <div data-index="0" style="height: 10px;">
-    <div class="van-index-anchor van-index-anchor--sticky van-hairline--bottom" style="transform: translate3d(0, 0px, 0); color: rgb(7, 193, 96); z-index: 1;">1</div>
+    <div class="van-index-anchor van-index-anchor--sticky van-hairline--bottom" style="position: relative; z-index: 1; transform: translate3d(0, 0px, 0); color: rgb(7, 193, 96);">1</div>
   </div>
   <div data-index="1" style="height: 10px;">
-    <div class="van-index-anchor van-index-anchor--sticky van-hairline--bottom" style="transform: translate3d(0, 10px, 0); color: rgb(7, 193, 96); z-index: 1;">2</div>
+    <div class="van-index-anchor van-index-anchor--sticky van-hairline--bottom" style="position: relative; z-index: 1; transform: translate3d(0, 0px, 0); color: rgb(7, 193, 96);">2</div>
   </div>
   <div data-index="2">
     <div class="van-index-anchor">3</div>