問題闡述：

在寫微信小程式時需要用到tabBar這個功能，但是在app.json檔案中寫好pages和tabBar儲存重新整理編譯後，預覽頁面中沒有顯示底部tab

"pages": [
    "pages/index/index",
    "pages/todo/todo",
    "pages/diary/diary",
    "pages/record/record"
  ],
  
"window": {
    "backgroundColor": "#F6F6F6",
    "backgroundTextStyle": "light",
    "navigationBarBackgroundColor": "#F6F6F6",
    "navigationBarTitleText": "demo",
    "navigationBarTextStyle": "black"
  },
  
"tabBar": {
    "list": [{
      "pagePath": "pages/todo/todo",
      "text": "one"
    },{
      "pagePath": "pages/diary/diary",
      "text": "two"
    },{
      "pagePath": "pages/record/record",
      "text": "three"
    } ]
}
 

問題解決：

1、將pages中的tab頁面放到前面，但是index會無法顯示，頁面直接是tab內容

"pages": [
    "pages/todo/todo",
    "pages/diary/diary",
    "pages/record/record",
    "pages/index/index"
  ],

2、比較好的解決方法是讓 tabBar 中包含 index 初始頁面這一項

"tabBar": {
    "list": [{
      "pagePath": "pages/index/index",
      "text": "one"
    },{
      "pagePath": "pages/diary/diary",
      "text": "two"
    },{
      "pagePath": "pages/record/record",
      "text": "three"
    } ]
}
 

這樣問題就解決了，再次儲存重新整理編譯，底部成功顯示出tabBar