在tabBar中，当有4个图标时，在android中正常，但在ios中出现换行，背景变成黑色

"tabBar":{

"color":"#000",

"selectedColor":"#38c258",

"backgroundColor":"",

"borderStyle":"black",

"list":[

{

"pagePath":"pages/index/index",

"text":"购票",

"iconPath":"pages/img/gp.png",

"selectedIconPath":"pages/img/gp1.png"

},

{

"pagePath": "pages/common/index",

"text": "乘车",

"iconPath": "pages/img/bs.png",

"selectedIconPath": "pages/img/bs1.png"

},

{

"pagePath": "pages/mine/index",

"text": "我的",

"iconPath": "pages/img/me.png",

"selectedIconPath": "pages/img/me1.png"

},

{

"pagePath": "pages/message/index",

"text": "消息",

"iconPath": "pages/img/message.png",

"selectedIconPath": "pages/img/message1.png"

}

]

}