B4J Question Changing the fill colour of a jGoogleMaps polygon

[Ralph Parkhurst]

I'm trying to change the fill colour of an existing jGoogleMaps polygon, when it is clicked.

By studying the GmapsFX api documentation here I tried this code - but it failed to work:

Private Sub GMap_PolygonClick (SelectedPolygon As MapPolygon)
    'change fill colour to green when the user clicks
    Private joFillColor = SelectedPolygon As JavaObject
    joFillColor = joFillColor.InitializeNewInstance("com.lynden.gmapsfx.shapes.Polygon", Null)
    joFillColor = joFillColor.RunMethod("setProperty", Array As Object("fillColor", Array As Object(fx.Colors.Green)))
End Sub

Where have I gone wrong?

Best regards,
Ralph

 

[DonManfred]

Do you get any error?

joFillColor = joFillColor.InitializeNewInstance("com.lynden.gmapsfx.shapes.Polygon", Null)

try to remove that line. You are creating a NEW Polygon here overwriting the existing.
InitializeNewInstance will create a new one with zero properties set and even this Polygon is not added to your GoogleMap too.
Setting a color to it will have no effect.

 

[Ralph Parkhurst]

Do you get any error?

No error is reported at all. And the polygon fill colour did not change.

try to remove that line.

Thanks for that suggestion, however unfortunately it did not help - again no error reported and no colour change.

 

[DonManfred]

You probably have to create a new PolygonOptions object and set the Fillcolor here.
replace the PolygonOptions in the Polygon then. But there is not method to set a new PolygonOptions.

Guess you have to remember the PolygonOptions you use when filling the Map.

Change the right PolygonOptions for the Polygon clicked.

 

[Ralph Parkhurst]

You probably have to create a new PolygonOptions object and set the Fillcolor here.
replace the PolygonOptions in the Polygon then. But there is not method to set a new PolygonOptions.

Guess you have to remember the PolygonOptions you use when filling the Map.

Change the right PolygonOptions for the Polygon clicked.

That sounds like a good suggestion. It might be a bit beyond my current understanding, but I will give it a shot and report back. And if nothing else I will learn along the way.

 

[DonManfred]

It might be a bit beyond my current understanding

post the code you use to create the polygon and adding them to the map.

I have to add that i never used GoogleMaps in B4J, only B4A.

 

[Ralph Parkhurst]

Yes, there do seem to be some differences between B4A and J when it comes to implementation of Google Maps.

Here is the code I used to add the initial polygon:

gmap.AddPolygon(lstPointsLatLng, LineWidthPolygon, LineColorPolygon, FillColorPolygon, OpacityPolygon)

where my variables are:
lstPointsLatLng is a list of LatLng coordinates,
LineWidthPolygon is the stroke width,
LineColorPolygon is the stroke colour,
FillColorPolygon is the Fill Color, and
OpacityPolygon is the Opacity.

One other way I thought of is to create two polygons, each with a different colour. Then alternate their visibility when the user clicks. I've tested that this works, however will require some more effort to manage the extra polygons.

 

[DonManfred]

Here is the code I used to add the initial polygon

i already thought so. I checked the Library code.

The PolygonOptions is used internally but you do not have access to it.

B4J/Libs_GoogleMaps/src/anywheresoftware/b4j/googlemaps/GoogleMapWrapper.java at master · AnywhereSoftware/B4J

B4J core libraries. Contribute to AnywhereSoftware/B4J development by creating an account on GitHub.

github.com

Starting at line 523

/**
     * Adds a polygon to the map.
     *Points - A list or array of LatLng points.
     *StrokeWidth - Stroke width.
     *StrokeColor - Stroke color.
     *FillColor - Inner color.
     *Opacity - Inner color opacity. Value between 0 to 1.
     */
    public PolygonWrapper AddPolygon(List Points, float StrokeWidth, Paint StrokeColor, Paint FillColor, double Opacity)
    {
        PolygonOptions po = new PolygonOptions();
        po.strokeWeight(StrokeWidth);
        po.fillColor(htmlColor(FillColor));
        po.strokeColor(htmlColor(StrokeColor));
        po.fillOpacity(Opacity);
        boolean eventExist = ba.subExists(eventName + "_polygonclick");
        if (eventExist == false)
            po.clickable(false);
        po.paths(new MVCArray(Points.getObject().toArray()));
        Polygon gon = new Polygon(po);
        map.addMapShape(gon);
        if (eventExist) {
            map.addUIEventHandler(gon, UIEventType.click, new UIEventHandler() {
                @Override
                public void handle(JSObject obj) {
                    ba.raiseEventFromUI(GoogleMapWrapper.this, eventName + "_polygonclick",
                            (PolygonWrapper)AbsObjectWrapper.ConvertToWrapper(new PolygonWrapper(), gon));
                }
            });
        }
        return (PolygonWrapper)AbsObjectWrapper.ConvertToWrapper(new PolygonWrapper(), gon);

    }

I guess one have to change the library to add the possibility to access the PolygonOptions.

 

[TILogistic]

options see:

GoogleMapsDemo

Some time ago I played a lot with GoogleMaps according to this post: https://www.b4x.com/android/forum/threads/problem-with-googlemaps-handling-polygons.84238/#post-533844 The problem was to add other shapes on a googlemap overlapping existing shapes. When you move the mouse over an existing...

www.b4x.com

 

[klaus]

The GoogleMaps demo in the link in the previous post does not have the possibility to change the color of a polygon.
I have also searched for a solution and came to the same conclusion as DonManfred.

 

[Ralph Parkhurst]

Thank you everyone. The method I am currently using is actually based on your idea Klaus - using Canvas to overlay a border in a different colour. But I thought if I could directly change the fill colour of the polygon all would be easier (and nicer!). I think I will pursue Plan-B - two polygons with different fill colours, and switch visibility. If this creates a workable and manageable solution I will revert back with my finding.

Warm regards,
Ralph

 

[TILogistic]

It's because I suggested the link above, it's because it has a lot of logic to work with polygons with canvas.

In the click event you can see the logic of how to handle polygons.

Regards.

 

[Ralph Parkhurst]

In the click event you can see the logic of how to handle polygons.

Great insight - thank you. I will study this closely.