修复返回首页时按钮消失问题

- onShow中恢复按钮位置和显示状态
- 确保从其他页面返回时按钮正确显示

pages/index/index.js

@@ -224,6 +224,26 @@ Page({
     const app = getApp();
     app.updateCurrentTab('index');
     app.globalData.showTabBar = true;
+    
+    const savedBtnTop = wx.getStorageSync('sidebarBtnTop');
+    const savedBtnHidden = wx.getStorageSync('sidebarBtnHidden');
+    const systemInfo = wx.getSystemInfoSync();
+    const screenHeight = systemInfo.screenHeight * 2;
+    
+    let defaultTop = screenHeight * 0.5;
+    if (savedBtnTop !== '' && savedBtnTop !== -100) {
+      const minTop = screenHeight * 0.2;
+      const maxTop = screenHeight * 0.6;
+      if (savedBtnTop >= minTop && savedBtnTop <= maxTop) {
+        defaultTop = savedBtnTop;
+      }
+    }
+    
+    this.setData({
+      sidebarBtnTop: defaultTop,
+      sidebarBtnHidden: savedBtnHidden || false
+    });
+    
     this.checkAndRestoreLoginStatus()
   },