1、获取设备信息
const systemInfo = wx.getSystemInfoSync();
2、获取设备栏高度
const statusBarHeight = Number(systemInfo.statusBarHeight);
3、获取导航栏高度
const menu = wx.getMenuButtonBoundingClientRect()
const navBarHeight = menu.height + (menu.top - statusBarHeight) * 2
4、设备栏加导航栏高度
const navStatusBarHeight = statusBarHeight + navBarHeight
5、底部黑条高度(仅iphoneX + 机型)
const safeBarHeight = systemInfo.screenHeight-systemInfo.safeArea.bottom