The latLng obtained through onTap of MapOptions is inaccurate

[antu58]

MapOptions mapOptions() {
return MapOptions(
center: LatLng(39.9091, 116.3941,),
minZoom: 2.0,
maxZoom: 18,
zoom: 16.0,
onTap: (LatLng latLng) {
//It looks different from the position touched by the hand
}
);
}

[ibrierley]

How far out is it ? What happens if you place a marker at the latlng ?

[Zzerr0r]

you probably didnt center your marker correctly on the latlng, the position is accurate from what i experienced

[cyrilhl]

No, this issue can simulate if you tap the map after zoom. If you did not zoom the map before tap, the latLng obtained is correct, but not after zoom. I think this is a bug on calculate the tap location without getting the latest zoom value.

[github-actions]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 5 days.

[Zzerr0r]

@cyrilhl why do you think its inaccurate? how do you come to the conclusion?

[ibrierley]

It works fine for me, so someone who has the problem needs to nail it down more and make it reproducible (I've tried with the basics at the top of the issue adding a marker in where I tap after a zoom and it shows in the correct place).

Maybe record a video of it appearing in the wrong place with the exact code being used.

These are my mapOptions I was testing with.

                options: MapOptions(
                    onTap: (tapPos, LatLng latLng) {
                      print("TAP $tapPos    $latLng");
                      markers.add(
                        Marker(
                          point: latLng,
                          builder: (ctx) => Icon(Icons.favorite),

                        ),
                      );
                      setState(() {

                      });
                    },
                  center: LatLng(51.5, -0.09),
                  zoom: 5.0,
                  maxZoom: 15.0,
                  minZoom: 0.0,
                    //interactiveFlags: InteractiveFlag.all & ~InteractiveFlag.rotate
                ),

[cyrilhl]

Please review the screen record that can reproduce the issue, my device is one plus 3T with lineage os
https://drive.google.com/file/d/15jmcGQD-IQ5VdpebQTA9o-LOue_qLb_e/view?usp=sharing

I am on Flutter 2.5.3 with getx 4.6.1, and attached with the widget for your reference.
flutter-map-on-tap-issue.zip

[JaffaKetchup]

This screen recording shows that the marker moves to the correct location, after another location has been pressed: ie. it is accurate, but delayed.

This may be something to do with your state management solution, or it may be a bug in flutter_map. It just seems the widget doesn't get rebuilt correctly.

[cyrilhl]

The marker is totally not on the location where I tap at the last 10 sec in my video, I know don't why you can say that is still accurate. I suggested you to download the whole video onto you computer to see instead of directly on google drive, since that is compressed on preview and the timing is really different after you download.

I agree that state management solution can be one of the cause, but this cannot explain the different between the tap location before and after zoom.

[JaffaKetchup]

Sorry, my mistake. Wasn't showing me the whole video for some reason. Now I can see that it does get less accurate the more zooming is done.

[cyrilhl]

If state management cause the issue, most likely the location is always incorrect, but inside my code I use the lat lng directly to create the marker, so I don't think this is the root cause.

And I use Getx in all of my projects, it can compatible will all packages on pub.dev, I think flutter map can compatible with it without any special handling

[ibrierley]

I note you are using nonrotatedchildren and layers....is it possible you are rotating the map when zooming, and you can't see that or something. To isolate, try adding interactiveFlags: InteractiveFlag.all & ~InteractiveFlag.rotate to your mapoptions and see if the behaviour is the same.

[cyrilhl]

Thank you so much, since my client required to disable the rotation on map, so that the reason I using nonrotated children and layers.
And after setting the "interactiveFlags: InteractiveFlag.all & ~InteractiveFlag.rotate", the tap location is correct no matter zoom in or out. Thank you so much !!