Simple way to Display GeoJSON Shapes (with GPS-Mark for current possition)

fridlmue · 11 February 2021 09:13

I would be Happy for Input on this Topic if someone knows a little about it or has some Idea. The solution should be Harbour compatible. All Input to steer my thoughts in a good direction are welcome!

I want to display the shapes of one or several GeoJSON-Files somehow in a scroll- and zoom-able component in a QML/Silica Application. On a click into a shape, I want to create an action, that displays for example more content for this shape.

Further I would like to display in the End an Indication of the current GPS position.

So in fact it is a really, really basic “Maps” application. But I’m not sure what are the best components to look into to realize that. I even thought about creating something that is feed to a browser view for that task. But I’m sure there are smarter ways to do that. Any Ideas welcome

michfu · 11 February 2021 14:39

I did this long ago for a parking ticket app, but never published this part.

github.com

fuchsmich/kurzpark/blob/049c11085b043b580dc01b36fcfce32eb312c871/qml/pages/MapPage.qml#L73


    doc.onreadystatechange = function() {
        if (doc.readyState === XMLHttpRequest.DONE && doc.readyState === XMLHttpRequest.DONE) {
            var arr = JSON.parse(doc.responseText);
            addWienFeatures(arr.features);
        }
    }
    doc.open("GET", jsonurl);
    doc.send();
}
function addWienFeatures(features) {
    //            bla[[1,2,3]]
    //            bla[0][0]
    //            console.log(features.length);
    for (var i = 0; i < features.length; ++i ){
        //                console.log(features[i].id)
        var dauer = features[i].properties.DAUER.replace(",",".")
        dauer = dauer.substring(0,dauer.length-1)
        if (features[i].geometry.type === "MultiPolygon") {
            var coordArr = features[i].geometry.coordinates;
            for (var j=0; j < coordArr.length; ++j) {

Keep in mind, this was my first app I ever wrote so the style may be not exactly “best practice” …and I’m not sure if the Map item is even still available on SailfishOS.

fridlmue · 11 February 2021 14:48

This looks Interesting, I’ll study it a little.

I’m not sure, if the Map item is from Silica (i don’t think so…) or from QtPositioning (which is available for Harbour) or QtLocation (which isn’t).

EDIT: It is from QtLocation, so no way for Harbour compliant Apps at the moment i think… QtLocation since 5.13 would have a GeoJSON component as well.

michfu · 11 February 2021 14:55

There was a lot of talk about maps and qtlocation in the community meetings. @rinigus should be competent in this topic.

fridlmue · 11 February 2021 14:58

Yeah, I’m aware. I thought, as I don’t really need underlying ‘Map’ with Map Tiles etc., there could be a smart and easy solution that I didn’t think about yet… At least I hope there is

fridlmue · 12 February 2021 11:47

I played around with it today. It works for ‘non-harbour’ applications with
- qt5-qtdeclarative-import-location in the .yaml-file and import QtLocation in the .qml-file.
However, as expected, the rpm-validator does not accept that for harbour.
Thanks, @michfu for the Ideas so far!

(Btw., https://sailfishos.org/wiki/Positioning indicates somehow that it could be allowed, I would recommend Jolla to change the text there…)