B4J Question RunFunctionWithResult returns an empty variable

[Mostez]

I have a Java script that returns user geolocation, I tested the script with Chrome developer tools and it runs with no problems, the problem is it returns an empty result to B4J server!
Your help is appreciated to solve this problem.
TIA

[CODE lang="html" title="HTML page"]<button class="btnlocation" type="submit" id="location" >Location</button>[/CODE]
[CODE lang="javascript" title="Java Script"] function getlocation() {
// var JSONobj = {};
if (navigator.geolocation) {
return new Promise((resolve, reject) => {
navigator.geolocation.getCurrentPosition(function (position) {
JSONobj = {
lat: position.coords.latitude,
long: position.coords.longitude,
success: true,
error: null,
message: '',
};
resolve(JSONobj);
}, function (error) {
JSONobj = {
lat: null,
long: null,
success: false,
error: error.code,
message: error.message,
};
//reject(error);
resolve(JSONobj);
},
//options
{
maximumAge: 3000,
timeout: 60000,
enableHighAccuracy: true,
});
});
} else {
// Handle error
}
}

async function getGeolocationData() {
const retJSONobj = await getlocation();
console.log(retJSONobj); //logs OK in console
return (retJSONobj);
// Use the geolocation data in your application
}[/CODE]

[CODE lang="json" title="Chrome Console"]{
"lat": xx.xx,
"long": xx.xx,
"success": true,
"error": null,
"message": ""
}[/CODE]

[CODE lang="b4x" title="B4J"]Sub Location_Click(Params As Map)
Dim f As Future = ws.RunFunctionWithResult("getGeolocationData", Null)
Log(f.Value)
ws.Flush
'logs these two lines,
'Waiting for value (100 ms)
'{}
End Sub[/CODE]

 

[Erel]

async await will not work as the function call will end before the result is available. You should wait for the result in JS. It can't be an async function.

 

[Mostez]

You should wait for the result in JS

if you don't mind, show how to wait for the result? this is a modified version with callback, but is also returns null!

        function getLocation(successCallback, errorCallback) {
            if (navigator.geolocation) {
                navigator.geolocation.getCurrentPosition(successCallback, errorCallback, {
                    maximumAge: 3000,
                    timeout: 60000,
                    enableHighAccuracy: true,
                });
            } else {
                // Handle error
            }
        }

        function getGeolocationData() {
            // Call the getLocation() function and pass in callback functions.
            getLocation((position) => {
                 //The user's position is available.
                              const JSONobj = {
                                  lat: position.coords.latitude,
                                  long: position.coords.longitude,
                                  success: true,
                                  error: null,
                                  message: "",
                              };
                        const strRetJSONobj = JSON.stringify(JSONobj);
                        console.log(strRetJSONobj); //...OK
                        return ("OK"); //returns null in B4J
            }, (error) => {
                // The user's position could not be determined.
                              const JSONobj = {
                                  lat: null,
                                  long: null,
                                  success: false,
                                  error: error.code,
                                  message: error.message,
                              };
                              const strRetJSONobj = JSON.stringify(JSONobj);
                              console.log(strRetJSONobj); //...OK
                              return ("!OK");  //returns null in B4J
              
            });
            
        }

 

[Erel]

It cannot work. The callback is executed after the B4J method already returned.

You need to use b4j_raiseevent to make the client call the server: https://www.b4x.com/android/forum/threads/evalwithresult-promises-solved.133257/