Geolocation HTML5 enableHighAccuracy True , False or Best Option? - html

i have a problem about HTML5 geolocation feature. I use the code below to get location data. I use "enableHighAccuracy: false" option to work with Cell Based GPS feature. Accurancy is low but response it too fast. But some people always use Built-in GPS with their mobile phone, so this code does not work for them. Bu if i change accurency option as "enableHighAccuracy: true" it works for them. But this time, the code uses only built-in GPS. not CELL based GPS.
The question -> How can i do that : First, try to get position from Built-in GPS with timeout (e.g. 5000ms ) if position cannot be got in this time just look for Cell Based position for timeout (e.g. 10000ms) if position cannot be get in this time, return an error message .
Here is the code that i use now.
Thanks in advance.
function getLocationfromGoogle() {
navigator.geolocation.getCurrentPosition(
function(pos) {
$("#lat_field").val(pos.coords.latitude);
$("#long_field").val(pos.coords.longitude);
var geocoder = new google.maps.Geocoder();
var latLng = new google.maps.LatLng(pos.coords.latitude,pos.coords.longitude);
geocoder.geocode({ 'latLng': latLng}, function (results, status) {
if (status == google.maps.GeocoderStatus.OK) {
//console.log(results[0].formatted_address);
$("#adresim").val(results[0].formatted_address);
}
else {
alert('Google convertion is not succesfully done.');
}
});
},function error(msg){
alert('Please enable your GPS position future.');
},{maximumAge:600000, timeout:5000, enableHighAccuracy: false}
);
}

You should also be aware that the implementation of this varies from phone OS to phone OS - what works on Android may or may not work on iOS, BlackBerry, WindowsPhone, etc.
You're almost there, you just need to:
Specify enableHighAccuracy: true (you have it set to false)
Handle the timeout error case in the error handler. If the error from the high accuracy query is timeout, then try it again with enableHighAccuracy: false.
Have a look at this sample code.
You should also note that when testing this on a few devices, it returns location derived from WiFi even when enableHighAccuracy: true.

The code mentioned here: http://jsfiddle.net/CvSW4/ did not work for me during error handling.
The reason is that the error functions accept a parameter named 'position' but use an object in the functions called 'error'.
function errorCallback_highAccuracy(position) { ... }
function errorCallback_lowAccuracy(position) { ... }
The solution to fix this was to switch the error methods to accept the input value as a parameter named 'error' and not 'position', since the error callbacks do not accept a position and throw an error object instead.
function errorCallback_highAccuracy(error) { ... }
function errorCallback_lowAccuracy(error) { ... }
I mention it here, because I could not post on the resulting example page and also, this is the location where I linked through to find the code sample mentioned above.

Related

Geolocation.currentLocation() not working, giving null value using meteor(1.5.1) & mdg:geolocation(1.3.0)

I am working in a meteor project(1.5.1) and using mdg:geolocation#1.3.0, and i am trying to get the value of Geolocation.currentLocation() but it is giving me null value and the behaviour is not the same for all the time, sometime it is giving me null value and sometime giving me proper value.
I have research for the long time, but not got the solution yet, if possible please provide solution with meteor#1.5.1 and with use of mdg:geolocation package.
Thanks in advance...
MDG has implemented mdg:geolocation for continuous geolocation and functions in this Meteor package return a reactive var. You can use the package this way (for example):
// Continous geolocation with mdg:geolocation
// This code will run every time user location changes.
Tracker.autorun(() => {
const position = Geolocation.currentLocation();
Tracker.nonreactive(() => {
if (position) {
Meteor.call('user.update.position', position);
}
});
});
If you don't need continous geolocation, You can use javascript method instead of meteor package. See this answer for other options with windows.navigator.geolocation. In this case you may need to add cordova-plugin-geolocation in case you are building Android or iOS apps
// Navigation geolocation to get geolocation only once
let errorCallback;
let successCallback;
successCallback = position => Meteor.call('user.update.position', position);
errorCallback = err => console.log(err);
navigator.geolocation.getCurrentPosition(successCallback, errorCallback, {
maximumAge: 60000,
timeout: 20000
});

chrome.storage.sync vs chrome.storage.local

I was trying to understand how to use the chrome.storage.api.
I have included the following in my manifest.json:
"permissions": [
"activeTab","storage"
],
Than, I opened a new tab with the devtools and switched the <page context> to the one of my chrome-extension. Than I typed:
chrome.storage.sync.set({"foo":"bar"},function(){ console.log("saved ok"); } );
and got:
undefined
saved ok
Than I tried getting this stored value:
chrome.storage.sync.get("foo",function(data){ console.log(data); } );
but this got me:
undefined
Object {}
Than I did the same, but instead of sync I used local and this worked as expected:
chrome.storage.local.set({"foo":"bar"},function(){ console.log("saved ok"); } );
..and the retrieval:
chrome.storage.local.get("foo",function(data){ console.log(data); } );
Which got me: Object {foo: "bar"} as it should.
Is this because I am not signed in to my account on chrome? But in that case, isn't chrome.storage.sync designed to fallback into storing the data locally?
EDIT
Strangely, when i type this straight on console it seems to be working, but this code doesn't run from background.js code inside a click listener:
var dataCache = {};
function addStarredPost(post)
{
var id = getPostId(post);
var timeStamp = new Date().getTime();
var user = getUserName();
dataCache[id] = {"id":id,"post":post,"time":timeStamp,"user":user};
chrome.storage.sync.set(dataCache,function(){ console.log("Starred!");});
}
After this is ran, chrome.storage.sync.get(null,function(data){ console.log(data); }); returns an empty object as if the data wasn't stored. :/
This code seems to be working perfect with chrome.storage.local instead.
chrome.runtime.lastErros returns undefined
The max size for chrome local storage is 5,242,880 bytes.
To extend the storage you can add on the manifest.json :
"permissions": [
"unlimitedStorage"
]
The max size for chrome sync storage is:
102,400 bytes total
8,192 bytes per item
512 items max
1,800 write operations per hour
120 operations per minutes
(source)
Whoops!
The problem was I was trying to sync data that exceeded in size. (4096 Bytes per item)
I wasn't getting chrome.runtime.lastError because I was mistakenly putting it inside the get function scope, instead of the set function which was producing the error. Hence, I'm posting this answer so it might help others who share the same confusion.
You should check chrome.runtime.lastError inside each api call, like so:
chrome.storage.local.set(objectToStore, function(data)
{
if(chrome.runtime.lastError)
{
/* error */
console.log(chrome.runtime.lastError.message);
return;
}
//all good. do your thing..
}
This ran OK with chrome.storage.local because according to the docs you only have this limitation with sync.
printing chrome.runtime.lastError gave me: Object {message: "QUOTA_BYTES_PER_ITEM quota exceeded"}

How do you detect that a script was loaded *and* executed in a chrome extension?

I've been tracking down a bug for days... then I realized the bug was me. :/
I had been using webRequest.onComplete, filtered for scripts. My error was that I made the incorrect association between the scripts being loaded and being executed. The get loaded in a different order than they get executed, and thus the timing of the events is not in the order I need them in. I need to inject between certain scripts so I need an event right after a file has been executed and before the next one.
The only solution I can think of at the moment is to alter the JS being loaded before it gets executed. But it makes my stomach turn. And the bfcache would wreak even more havoc, so not a great solution either.
I would use the HTML5 spec's afterscriptexecute, but that is not implemented in Chrome. Is there another API, perhaps an extension API that I can use?
Note: This method no longer works as of Chrome 36. There are no direct alternatives.
Note: The answer below only applies to external scripts, i.e. those loaded with <script src>.
In Chrome (and Safari), the "beforeload" event is triggered right before a resource is loaded. This event allows one to block the resource, so that the script is never fetched. In this event, you can determine whether the loaded resource is a script, and check whether you want to perform some action
This event can be used to emulate beforescriptexecute / afterscriptexecute:
document.addEventListener('beforeload', function(event) {
var target = event.target;
if (target.nodeName.toUpperCase() !== 'SCRIPT') return;
var dispatchEvent = function(name, bubbles, cancelable) {
var evt = new CustomEvent(name, {
bubbles: bubbles,
cancelable: cancelable
});
target.dispatchEvent(evt);
if (evt.defaultPrevented) {
event.preventDefault();
}
};
var onload = function() {
cleanup();
dispatchEvent('afterscriptexecute', true, false);
};
var cleanup = function() {
target.removeEventListener('load', onload, true);
target.removeEventListener('error', cleanup, true);
}
target.addEventListener('error', cleanup, true);
target.addEventListener('load', onload, true);
dispatchEvent('beforescriptexecute', true, true);
}, true);
The dispatch times are not 100% identical to the original ones, but it is sufficient for most cases. This is the time line for the (non-emulated) events:
beforeload Before the network request is started
beforescriptexecute Before a script executes
afterscriptexecute After a script executes
onload After the script has executed
Here's an easy way to see that the events are working as expected:
window.addEventListener('afterscriptexecute', function() {
alert(window.x);
});
document.head.appendChild(document.createElement('script')).src = 'data:,x=1';
document.head.appendChild(document.createElement('script')).src = 'data:,x=2';
The demo can be seen live at http://jsfiddle.net/sDaZt/
I'm not familiar with Chrome Extensions (only browser javascript), but I think that you will unfortunately have to edit your loaded JS so that is calls a function of your choice when it is executed, if you want to do this nicely. This it what Google does for asynchronously loading its Maps Javascript file:
function loadScript() {
var script = document.createElement("script");
script.type = "text/javascript";
script.src = "http://maps.googleapis.com/maps/api/js?sensor=false&callback=executed";
document.body.appendChild(script);
}
function executed() {
/* Google maps has finished loading, do awesome things ! */
}
If you really don't want to edit your loaded JS files, you could have a setInterval (or a recursive function with setTimeout) checking regularly if some functions or variables are initialized.
Have you tried script loading using Modernizr.js?
I had a similar issue, where the timing of script loading was causing conflict. I used Modernizr.js, which includes the library yepnope.js by default. Below is an example of some scripts I loaded conditionally. You can include a test clause, or simply load them in the order you prefer, with the guarantee that they will load and execute in the order you wish due to the callback.
Here is an example with a conditional clause:
Modernizr.load({
test: false, //Or whatever else you'd like. Can be conditional, or not so conditional
yep: {
'script1': 'MyJavascriptLibrary1.js'
},
nope: {
'script2': 'MyJavascriptLibrary2.js',
'script3': 'MyJavascriptLibrary3.js'
},
callback: {
'script1': function (url, result, key) {
console.log('MyJavascriptLibrary1.js loaded'); //will not load in this example
},
'script2': function (url, result, key) {
console.log('MyJavascriptLibrary2.js loaded first');
},
'script3': function (url, result, key) {
console.log('MyJavascriptLibrary3.js loaded second');
}
}
});
If triggering false, MyJavascriptLibrary2.js and MyJavascriptLibrary3.js will load in the appropriate order, no matter what elements influence how they would behave normally (file size, connection speed, etc.). In these callbacks, you may fire additional javascript as well, in the order you wish to do so. Example:
'script2': function (url, result, key) {
alert('anything in here will fire before MyJavascriptLibrary3.js executes');
},
Note this can be done without Modernizr.load({...
but using simply yepnope({...
For more documentation, check out the yepnope.js API

google maps reverse geocoding: passing variables

I am trying to get store the address correspoding to a latitude,longitude in a variable (in javascript). I created a call back function (after reading numerous posts on it) and the code is as follows. Now I want to store the address in a variable called location3.
Oddly enough, for an alert right after location3 is assigned, it is undefined. But if it is looked at 300ms later, then it gives the right value. I want to get the address assigned to location3 immediately. Any suggestions are welcome.
function codeLatLng1(lat,long,callback) {
var geocoder = new google.maps.Geocoder();
var latlng = new google.maps.LatLng(lat,long);
if (geocoder) {
geocoder.geocode({'latLng': latlng}, function(results, status) {
if (status == google.maps.GeocoderStatus.OK) {
if (results[1]) {
callback(results[1].formatted_address);
myvariable=results[1].formatted_address;
} else {
alert("No results found");
}
} else {
alert("Geocoder failed due to: " + status);
}
});
}
}
lat1_last=37;long1_last=-100;
codeLatLng1(lat1_last,long1_last,function(locat) {location3=locat;});
alert (location3); // THIS ALERT SHOWS THAT IT IS STILL UNDEFINED
setTimeout(function(){alert (location3);},300); // THIS ALERT GIVES THE RIGHT ADDRESS
The idea to grasp here is that the 2nd argument to geocode(), a callback function, is not going to be called right away, but rather only after a result is received from Google. Meanwhile, the function codeLatLng1(), having posted the request, returns control to the caller. In your program, that means the first alert() happens next, followed by some wait time during which Google gets back to you, the callback is called, and so on.
Likewise, your anonymous callback that sets location3 is only executed when that result is received - not before codeLatLng1 returns.
It would make more sense to put your alert inside your anonymous callback. Typically this is where final processing of the result goes.
This is an example of asynchronous or event-driven programming.
I hope this makes it clear!

HTML5 GEOLocation 2nd prompt

Is there a way to prompt user for geolocation again on some trigger, after they denied the location sharing?
navigator.geolocation.getCurrentPosition
fires it once, consecutive calls do not produce the same result. Cant find the answer anywhere/
Take a look at this Code Snippet and this SO Answer: What is the best JQuery plugin that handles HTML5 location?
if (navigator.geolocation) {
navigator.geolocation.getCurrentPosition(successFunction, errorFunction);
}else{
errorFunction();
}
function successFunction(position) { //uses HTML5 if available
var lat = position.coords.latitude;
var lng = position.coords.longitude;
}
function errorFunction(){ //uses IP if no HTML5
$.getJSON("http://freegeoip.net/json/", function(res){
var lat = res.latitude;
var lng = res.longitude;
});
}
Take a Look at this Fiddle Link also
JQuery Geolocator Plugin
In Geolocation API? No.
If user clicks deny permission it simply means "No, and don't bother me again..."
However user can do it by deleting Location-share-settings, then of course the prompt pops out again.
Or user can just change the settings if browser allows it, however e.g. Chrome manages these settings as exceptions (no matter whether user've allowed or denied permission) so user have to delete the settings, resp. exception anyway.
What now?
Your only option is to catch the error and use e.g. some external API to find the user's location by IP. You can program it by yourself or there are of course existing solutions as #Venkat suggested.
But be aware IP geolocation is a tricky one - sometimes it has an adress-number-accuracy sometimes it's just state-accuracy.
This examle from Mozilla's docs shows a nice example how to handle Geolocation errors:
var options = {
enableHighAccuracy: true,
timeout: 5000,
maximumAge: 0
};
function success(pos) {
var crd = pos.coords;
console.log('Your current position is:');
console.log('Latitude : ' + crd.latitude);
console.log('Longitude: ' + crd.longitude);
console.log('More or less ' + crd.accuracy + ' meters.');
};
function error(err) {
/*
CALL EXTERNAL API HERE
*/
console.warn('ERROR(' + err.code + '): ' + err.message);
};
navigator.geolocation.getCurrentPosition(success, error, options);
The best option for this is to setup a geolocation subdomain, and load it in a iframe.
geo-0.domain.com
geo-1.domain.com
geo-2.domain.com
geo-3.domain.com
geo-4.domain.com
geo-N.domain.com
This will allow you unlimited attempts on every browser, all you need to do is program in your own retry logic.