<view class="nav-bar"
  :style="{
    'height': navHeight + 'px'
  }">
</view>

data() {
  return {
    // 头部总高度,iPhone5/6/7/8默认64px
    navHeight:64,
  }
}
onLoad(params) {
  this.attached()
},
methods: {
  attached() {
    var that = this;
    wx.getSystemInfo({
      success: (result) => {
        if(result.statusBarHeight == 20) {
          this.navHeight = 64
        }else {
          this.navHeight = 88
        }
      },
    })
  },
}