小程序页面文件index.json修改navigationStyle为custom：
{
"usingComponents": {},
"navigationStyle": "custom"
}
wxml：
<view class="box-top"> <image class="box-top-pic" src="/images/top.png" mode="widthFix" /> </view>
wxss：
.box-top {
width: 100%;
background-color: #FC7322;
background: linear-gradient(to bottom, #FC7322, #ffffff);
padding-top: 20px;
padding: 0;
margin: 0;
}
.box-top-pic{
width:300%;
margin-left: -300px;
height: 200px;
}