diff --git a/src/core/wrapper/layout.js b/src/core/wrapper/layout.js
index 6649f55bb..66fa3f17e 100644
--- a/src/core/wrapper/layout.js
+++ b/src/core/wrapper/layout.js
@@ -578,76 +578,6 @@ export class Layout extends Widget {
         let before;
         let updated;
         const children = {};
-        each(oldCh, (i, child) => {
-            child = this._getOptions(child);
-            const key = isNull(child.key) ? i : child.key;
-            if (isKey(key)) {
-                children[key] = this._children[this._getChildName(i)];
-            }
-        });
-
-        while (oldStartIdx <= oldEndIdx && newStartIdx <= newEndIdx) {
-            if (isNull(oldStartVnode)) {
-                oldStartVnode = oldCh[++oldStartIdx];
-            } else if (isNull(oldEndVnode)) {
-                oldEndVnode = oldCh[--oldEndIdx];
-            } else if (sameVnode(oldStartVnode, newStartVnode, oldStartIdx, newStartIdx)) {
-                const willUpdate = this.patchItem(oldStartVnode, newStartVnode, oldStartIdx, newStartIdx);
-                updated = willUpdate || updated;
-                children[isNull(oldStartVnode.key) ? oldStartIdx : oldStartVnode.key] = willUpdate ? this._children[`${this._getChildName(newStartIdx)}-temp`] : this._children[this._getChildName(oldStartIdx)];
-                oldStartVnode = oldCh[++oldStartIdx];
-                newStartVnode = newCh[++newStartIdx];
-            } else if (sameVnode(oldEndVnode, newEndVnode, oldEndIdx, newEndIdx)) {
-                const willUpdate = this.patchItem(oldEndVnode, newEndVnode, oldEndIdx, newEndIdx);
-                updated = willUpdate || updated;
-                children[isNull(oldEndVnode.key) ? oldEndIdx : oldEndVnode.key] = willUpdate ? this._children[`${this._getChildName(newEndIdx)}-temp`] : this._children[this._getChildName(oldEndIdx)];
-                oldEndVnode = oldCh[--oldEndIdx];
-                newEndVnode = newCh[--newEndIdx];
-            } else if (sameVnode(oldStartVnode, newEndVnode)) {
-                const willUpdate = this.patchItem(oldStartVnode, newEndVnode, oldStartIdx, newStartIdx);
-                updated = willUpdate || updated;
-                children[isNull(oldStartVnode.key) ? oldStartIdx : oldStartVnode.key] = willUpdate ? this._children[`${this._getChildName(newStartIdx)}-temp`] : this._children[this._getChildName(oldStartIdx)];
-                insertBefore(oldStartVnode, oldEndVnode, true);
-                oldStartVnode = oldCh[++oldStartIdx];
-                newEndVnode = newCh[--newEndIdx];
-            } else if (sameVnode(oldEndVnode, newStartVnode)) {
-                const willUpdate = this.patchItem(oldEndVnode, newStartVnode, oldEndIdx, newEndIdx);
-                updated = willUpdate || updated;
-                children[isNull(oldEndVnode) ? oldEndIdx : oldEndVnode.key] = willUpdate ? this._children[`${this._getChildName(newEndIdx)}-temp`] : this._children[this._getChildName(oldEndIdx)];
-                insertBefore(oldEndVnode, oldStartVnode);
-                oldEndVnode = oldCh[--oldEndIdx];
-                newStartVnode = newCh[++newStartIdx];
-            } else {
-                const sameOldVnode = findOldVnode(oldCh, newStartVnode, oldStartIdx, oldEndIdx);
-                if (isNull(sameOldVnode[0])) { //  不存在就把新的放到左边
-                    const node = addNode(newStartVnode, newStartIdx, context);
-                    insertBefore(node, oldStartVnode);
-                } else { //  如果新节点在旧节点区间中存在就复用一下
-                    const sameOldIndex = sameOldVnode[1];
-                    const willUpdate = this.patchItem(sameOldVnode[0], newStartVnode, sameOldIndex, newStartIdx);
-                    updated = willUpdate || updated;
-                    children[isNull(sameOldVnode[0].key) ? newStartIdx : sameOldVnode[0].key] = willUpdate ? this._children[`${this._getChildName(newStartIdx)}-temp`] : this._children[this._getChildName(sameOldIndex)];
-                    oldCh[sameOldIndex] = undefined;
-                    insertBefore(sameOldVnode[0], oldStartVnode);
-                }
-                newStartVnode = newCh[++newStartIdx];
-            }
-        }
-        if (oldStartIdx > oldEndIdx) {
-            before = isNull(newCh[newEndIdx + 1]) ? null : newCh[newEndIdx + 1];
-            addVnodes(before, newCh, newStartIdx, newEndIdx, context);
-        } else if (newStartIdx > newEndIdx) {
-            removeVnodes(oldCh, oldStartIdx, oldEndIdx);
-        }
-
-        this._children = {};
-        each(newCh, (i, child) => {
-            const node = this._getOptions(child);
-            const key = isNull(node.key) ? i : node.key;
-            children[key]._setParent && children[key]._setParent(this);
-            children[key]._mount();
-            this._children[this._getChildName(i)] = children[key];
-        });
 
         const sameVnode = (vnode1, vnode2, oldIndex, newIndex) => {
             vnode1 = this._getOptions(vnode1);
@@ -720,6 +650,77 @@ export class Layout extends Widget {
             return [found, findIndex];
         };
 
+        each(oldCh, (i, child) => {
+            child = this._getOptions(child);
+            const key = isNull(child.key) ? i : child.key;
+            if (isKey(key)) {
+                children[key] = this._children[this._getChildName(i)];
+            }
+        });
+
+        while (oldStartIdx <= oldEndIdx && newStartIdx <= newEndIdx) {
+            if (isNull(oldStartVnode)) {
+                oldStartVnode = oldCh[++oldStartIdx];
+            } else if (isNull(oldEndVnode)) {
+                oldEndVnode = oldCh[--oldEndIdx];
+            } else if (sameVnode(oldStartVnode, newStartVnode, oldStartIdx, newStartIdx)) {
+                const willUpdate = this.patchItem(oldStartVnode, newStartVnode, oldStartIdx, newStartIdx);
+                updated = willUpdate || updated;
+                children[isNull(oldStartVnode.key) ? oldStartIdx : oldStartVnode.key] = willUpdate ? this._children[`${this._getChildName(newStartIdx)}-temp`] : this._children[this._getChildName(oldStartIdx)];
+                oldStartVnode = oldCh[++oldStartIdx];
+                newStartVnode = newCh[++newStartIdx];
+            } else if (sameVnode(oldEndVnode, newEndVnode, oldEndIdx, newEndIdx)) {
+                const willUpdate = this.patchItem(oldEndVnode, newEndVnode, oldEndIdx, newEndIdx);
+                updated = willUpdate || updated;
+                children[isNull(oldEndVnode.key) ? oldEndIdx : oldEndVnode.key] = willUpdate ? this._children[`${this._getChildName(newEndIdx)}-temp`] : this._children[this._getChildName(oldEndIdx)];
+                oldEndVnode = oldCh[--oldEndIdx];
+                newEndVnode = newCh[--newEndIdx];
+            } else if (sameVnode(oldStartVnode, newEndVnode)) {
+                const willUpdate = this.patchItem(oldStartVnode, newEndVnode, oldStartIdx, newStartIdx);
+                updated = willUpdate || updated;
+                children[isNull(oldStartVnode.key) ? oldStartIdx : oldStartVnode.key] = willUpdate ? this._children[`${this._getChildName(newStartIdx)}-temp`] : this._children[this._getChildName(oldStartIdx)];
+                insertBefore(oldStartVnode, oldEndVnode, true);
+                oldStartVnode = oldCh[++oldStartIdx];
+                newEndVnode = newCh[--newEndIdx];
+            } else if (sameVnode(oldEndVnode, newStartVnode)) {
+                const willUpdate = this.patchItem(oldEndVnode, newStartVnode, oldEndIdx, newEndIdx);
+                updated = willUpdate || updated;
+                children[isNull(oldEndVnode) ? oldEndIdx : oldEndVnode.key] = willUpdate ? this._children[`${this._getChildName(newEndIdx)}-temp`] : this._children[this._getChildName(oldEndIdx)];
+                insertBefore(oldEndVnode, oldStartVnode);
+                oldEndVnode = oldCh[--oldEndIdx];
+                newStartVnode = newCh[++newStartIdx];
+            } else {
+                const sameOldVnode = findOldVnode(oldCh, newStartVnode, oldStartIdx, oldEndIdx);
+                if (isNull(sameOldVnode[0])) { //  不存在就把新的放到左边
+                    const node = addNode(newStartVnode, newStartIdx, context);
+                    insertBefore(node, oldStartVnode);
+                } else { //  如果新节点在旧节点区间中存在就复用一下
+                    const sameOldIndex = sameOldVnode[1];
+                    const willUpdate = this.patchItem(sameOldVnode[0], newStartVnode, sameOldIndex, newStartIdx);
+                    updated = willUpdate || updated;
+                    children[isNull(sameOldVnode[0].key) ? newStartIdx : sameOldVnode[0].key] = willUpdate ? this._children[`${this._getChildName(newStartIdx)}-temp`] : this._children[this._getChildName(sameOldIndex)];
+                    oldCh[sameOldIndex] = undefined;
+                    insertBefore(sameOldVnode[0], oldStartVnode);
+                }
+                newStartVnode = newCh[++newStartIdx];
+            }
+        }
+        if (oldStartIdx > oldEndIdx) {
+            before = isNull(newCh[newEndIdx + 1]) ? null : newCh[newEndIdx + 1];
+            addVnodes(before, newCh, newStartIdx, newEndIdx, context);
+        } else if (newStartIdx > newEndIdx) {
+            removeVnodes(oldCh, oldStartIdx, oldEndIdx);
+        }
+
+        this._children = {};
+        each(newCh, (i, child) => {
+            const node = this._getOptions(child);
+            const key = isNull(node.key) ? i : node.key;
+            children[key]._setParent && children[key]._setParent(this);
+            children[key]._mount();
+            this._children[this._getChildName(i)] = children[key];
+        });
+
         return updated;
     }