在 app.json    文件里面 ：

{  "pages":[    "pages/index/index",    "pages/logs/logs",    "pages/topic/topic",    "pages/category/category"  ],  "window":{    "backgroundTextStyle":"light",    "navigationBarBackgroundColor": "#000",    "navigationBarTitleText": "大熊图书馆",    "navigationBarTextStyle":"white"  },  "tabBar": {    "color": "#8c8c8c",//字体颜色    "selectedColor": "#f4645f", //选中字体颜色    "backgroundColor": "#fff",//背景颜色    "list": [{      "pagePath": "pages/index/index",      "text": "图书",      "iconPath":"images/book.png",      "selectedIconPath":"images/book1.png"    },     {      "pagePath": "pages/category/category",            "text": "评论",      "iconPath":"images/book.png",      "selectedIconPath":"images/book1.png"    },    {      "pagePath": "pages/topic/topic",            "text": "我的",      "iconPath":"images/book.png",      "selectedIconPath":"images/book1.png"    }      ],    "position": "bottom"    //写成   top   就在上面  }  }