BangleApps/apps/mylocation/mylocation.app.js

Bangle.loadWidgets();
Bangle.drawWidgets();

const SETTINGS_FILE = "mylocation.json";
let settings;

// initialize with default settings...
let s = {
  'lat': 51.5072,
  'lon': 0.1276,
  'location': "London"
}

function loadSettings() {
  settings = require('Storage').readJSON(SETTINGS_FILE, 1) || s;
}

function save() {
  settings = s
  require('Storage').write(SETTINGS_FILE, settings)
}

const locations = ["London", "Newcastle", "Edinburgh", "Paris", "New York", "Tokyo","???"];
const lats = [51.5072 ,54.9783 ,55.9533 ,48.8566 ,40.7128 ,35.6762, 0.0];
const lons = [-0.1276  ,-1.6178  ,-3.1883  ,2.3522  , -74.0060 ,139.6503, 0.0];

function setFromGPS() {
  Bangle.on('GPS', (gps) => {
    //console.log(".");
    if (gps.fix === 0) return;
    //console.log("fix from GPS");
    s = {'lat': gps.lat, 'lon': gps.lon, 'location': '???' }
    Bangle.buzz(1500); // buzz on first position
    Bangle.setGPSPower(0);
    save();

    Bangle.setUI("updown", ()=>{ load() });
    E.showPrompt("Location has been saved from the GPS fix",{
      title:"Location Saved",
      buttons : {"OK":1}
    }).then(function(v) {
      load(); // load default clock
    });
  });

  Bangle.setGPSPower(1);
  E.showMessage("Waiting for GPS fix. Place watch in the open. Could take 10 minutes. Long press to abort", "GPS Running");
  Bangle.setUI("updown", undefined);
}

function showMainMenu() {
  console.log("showMainMenu");
  const mainmenu = {
    '': { 'title': 'My Location' },
    '<Back': ()=>{ load(); },
    'City': {
      value: 0 | locations.indexOf(s.location),
      min: 0, max: 6,
      format: v => locations[v],
      onchange: v => {
        if (v != 6) {
          s.location = locations[v];
          s.lat = lats[v];
          s.lon = lons[v];
          save();
        }
      }
    },
    'Set From GPS': ()=>{ setFromGPS(); }
  }
  return E.showMenu(mainmenu);
}

loadSettings();
showMainMenu();