自定义小程序导航栏，获取导航栏高度

let stateHeight = ""; //任务栏高度
wx.getSystemInfoAsync({
  success: (result) => {
    stateHeight = result.statusBarHeight; //状态栏高度
    let sum = "";
    sum = stateHeight + height + (top - stateHeight) * 2;
    this.height = sum;
  },
});