Titanium mapView radius slider

app.js

// this sets the background color of the master UIView (when there are no windows/tab groups on it)
Titanium.UI.setBackgroundColor('#000');

Ti.include('util.js');

var win = Titanium.UI.createWindow({  
    backgroundColor:'#fff'
});

var currentPosition = {}, 
radiusStartVal = 5,
radiusEndVal = 50,
radiusMultiplier = 5,
radiusStartPos = radiusStartVal / radiusMultiplier,
radiusEndPos = radiusEndVal / radiusMultiplier,
radius = radiusStartVal,
mapView = Titanium.Map.createView({
	top:0,
	bottom:0,
	left:0,
	right:0,
	mapType: Titanium.Map.STANDARD_TYPE,
	animate:true,
	regionFit:true,
	userLocation:false
}),
radiusSlider = Ti.UI.createSlider({
	min:radiusStartPos,
	max:radiusEndPos,
	top:10,
	width:150,
	value:radiusStartPos
}),
headerTitle = Ti.UI.createLabel({
	text:radius+' miles',
	top:32,
	textAlign:'center',
	color:'#333',
	font: {
		fontFamily:'Arial',
		fontSize:16
	},
	height:'auto'
});

win.add(mapView);
win.add(radiusSlider);
win.add(headerTitle);

win.addEventListener('focus', function(e) {
	getGeoLocation({
		success: function(geo) {
			// save current location 
			currentPosition = geo;
			
			// set the region
			var deltas = getDelta(currentPosition.latitude),
			region = {
				latitude:currentPosition.latitude, 
				longitude:currentPosition.longitude,
				latitudeDelta:deltas.latitudeDelta*radius, 
				longitudeDelta:deltas.longitudeDelta*radius
			};
			setTimeout(function() {
				mapView.setLocation(region);
			}, 400);
		},
		error: function(err) {
			alert(err);
		}
	});
});

radiusSlider.addEventListener('change', function(e) {
	var currRadius = radius,
	val = Math.floor(e.value),
	tmpRadius = val * radiusMultiplier;
	if (tmpRadius !== currRadius) {
		radius = tmpRadius;
		
		// set the title
		headerTitle.text = radius+' miles';
		
		var deltas = getDelta(currentPosition.latitude),
		set_region = {
			latitude:currentPosition.latitude, 
			longitude:currentPosition.longitude,
			latitudeDelta:deltas.latitudeDelta*radius, 
			longitudeDelta:deltas.longitudeDelta*radius
		};
		mapView.setLocation(set_region);
	}
});


win.open();

util.js

function isIPhone3_2_Plus() {
	// add iphone specific tests
	if (Titanium.Platform.name == 'iPhone OS') {
		var version = Titanium.Platform.version.split(".");
		var major = parseInt(version[0], 10);
		var minor = parseInt(version[1], 10);

		// can only test this support on a 3.2+ device
		if (major > 3 || (major == 3 && minor > 1)) {
			return true;
		}
	}
	return false;
};

function getGeoLocation(_args) {
	var geoResult = {};
	if (Titanium.Geolocation.locationServicesEnabled==false) {
		Titanium.UI.createAlertDialog({title:'Geolocation Disabled', message:'Your device has geo turned off - turn it on please.'}).show();
		geoResult.error = "Location services are disabled";
	} else {
		if (isIPhone3_2_Plus()) {
			Ti.Geolocation.purpose = "Testing Geolocation stuff";
		};
		var geoAllowed = true;
		if (Titanium.Platform.name != 'android') {
			var authorization = Titanium.Geolocation.locationServicesAuthorization;
			if (authorization == Titanium.Geolocation.AUTHORIZATION_DENIED) {
				Ti.UI.createAlertDialog({
					title:'Geo Denied',
					message:'Authorization Denied.'
				}).show();
				geoResult.error = "Geolocation access is denied";
			} else if (authorization == Titanium.Geolocation.AUTHORIZATION_RESTRICTED) {
				Ti.UI.createAlertDialog({
					title:'Geo Restricted',
					message:'Geolocation Restricted.'
				}).show();
				geoResult.error = "Geolocation access is restricted";
			}
		}
	
		if (!geoResult.error) {
			Titanium.Geolocation.getCurrentPosition(function(e) {
				if (!e.success || e.error) {
					alert('error ' + JSON.stringify(e.error));
					geoResult.error = e.error;
				}
			
				if (!geoResult.error) {
					var longitude = e.coords.longitude,
					latitude = e.coords.latitude,
					altitude = e.coords.altitude,
					heading = e.coords.heading,
					accuracy = e.coords.accuracy,
					speed = e.coords.speed,
					timestamp = e.coords.timestamp,
					altitudeAccuracy = e.coords.altitudeAccuracy;
				
					geoResult.longitude = longitude;
					geoResult.latitude = latitude;
				
					if (_args.success) {
						_args.success(geoResult);
					};
				}
			});
		}
	}
	if (geoResult.error) {
		if (_args.error) {
			_args.error(geoResult.error);
		};
	};
};

	
/////////////////////////////////////////////////////////////////////////
// code borrowed from http://www.csgnetwork.com/degreelenllavcalc.html //
/////////////////////////////////////////////////////////////////////////
function deg2rad(deg) {
	var conv_factor = (2.0 * Math.PI)/360.0;
	return(deg * conv_factor);
}

function rad2deg(rad) {
	var conv_factor = 360/(2.0 * Math.PI);
	return(rad * conv_factor);
}

function zerosPad(rndVal, decPlaces) {
	var valStrg = rndVal.toString(); // Convert the number to a string
	var decLoc = valStrg.indexOf("."); // Locate the decimal point
	// check for a decimal 
	if (decLoc == -1) {
		decPartLen = 0; // If no decimal, then all decimal places will be padded with 0s
		// If decPlaces is greater than zero, add a decimal point
		valStrg += decPlaces > 0 ? "." : "";
	} else {
		decPartLen = valStrg.length - decLoc - 1; // If there is a decimal already, only the needed decimal places will be padded with 0s
	}
	 var totalPad = decPlaces - decPartLen;    // Calculate the number of decimal places that need to be padded with 0s
	if (totalPad > 0) {
		// Pad the string with 0s
		for (var cntrVal = 1; cntrVal <= totalPad; cntrVal++) {
			valStrg += "0";
		}
	}
	return valStrg;
}

function perRound(num, precision) {
	var precision = 2; //default value if not passed from caller, change if desired
	// remark if passed from caller
	precision = parseInt(precision); // make certain the decimal precision is an integer
	var result1 = num * Math.pow(10, precision);
	var result2 = Math.round(result1);
	var result3 = result2 / Math.pow(10, precision);
	return zerosPad(result3, precision);
}

function getDelta (lat) {
	// Convert latitude to radians
	lat = deg2rad(lat);
	
	// Set up "Constants"
	m1 = 111132.92;		// latitude calculation term 1
	m2 = -559.82;		// latitude calculation term 2
	m3 = 1.175;			// latitude calculation term 3
	m4 = -0.0023;		// latitude calculation term 4
	p1 = 111412.84;		// longitude calculation term 1
	p2 = -93.5;			// longitude calculation term 2
	p3 = 0.118;			// longitude calculation term 3
	
	// Calculate the length of a degree of latitude and longitude in meters
	latlen = m1 + (m2 * Math.cos(2 * lat)) + (m3 * Math.cos(4 * lat)) +
			(m4 * Math.cos(6 * lat));
	longlen = (p1 * Math.cos(lat)) + (p2 * Math.cos(3 * lat)) +
			(p3 * Math.cos(5 * lat));
	
	// Place values in output fields
	var latmeters = (latlen);
	var latfeet = (latlen * (3.280833333));
	var latsm = latfeet / 5280;
	var latnm = latsm / 1.15077945;
	var longmeters = (longlen);
	var longfeet = (longlen * (3.280833333)   );
	var longsm = longfeet / 5280;
	var longnm = longsm / 1.15077945;
	
	// rounded
	var latmetersr = perRound(latlen);
	var latfeetr = perRound(latlen * (3.280833333));
	var latsmr = perRound(latfeet / 5280);
	var latnmr = perRound(latsm / 1.15077945);
	var longmetersr = perRound(longlen);
	var longfeetr = perRound(longlen * (3.280833333));
	var longsmr = perRound(longfeet / 5280);
	var longnmr = perRound(longsm / 1.15077945);
	
	var ret = {
		latitudeDelta:1 / latsm,
		longitudeDelta:1 / longsm
	};
	
	return ret;
}