How To Handle Wkt Data In Android?

June 08, 2023 Post a Comment

I have data in this format: POINT(73.0166738279393 33.6788721326803) MULTILINESTRING((73.0131224998036 33.679001500419,73.0119635003153 33.678392400389,73.0119205001311 33.67837810

Solution 1:

Try this ,

String str;
ArrayList<String> coordinates = newArrayList<String>();

First get string from textview.

str = textview.getText().toString();

Second remove brackets.

str = str.replaceAll("\\(", "");str = str.replaceAll("\\)", "");

Then split with comma and add values to arraylist.

String[] commatokens = str.split(",");
        for (String commatoken : commatokens) {
            System.out.println("-" + commatoken + "-");
            coordinates.add(commatoken);
        }

Then we get separate coordinates value at index position ,

for (int i = 0; i < coordinates.size(); i++) {

            String[] tokens = coordinates.get(i).split("\\s");
            for (String token : tokens) {
                System.out.println("-" + token + "-");
            }
        }

Solution 2:

For anyone else who has this same scenario, I found an open source library called JTS Topology Suite, which has the capability to parse WKT strings in Java. A basic example from my application looks like this:

WKTReaderwktReader=newWKTReader();
Geometrygeometry= wktReader.read(routeResponse.get(yourWKTMultilineString);

You can then iterate through the individual lines like so:

for(intlineIndex=0; lineIndex < geometry.getNumGeometries(); lineIndex++){
    GeometrylineGeometry= geometry.getGeometryN(lineIndex);
    //... other stuff
}

If necessary, you can obtain the individual coordinates of each line like so:

Coordinate[] lineCoordinates = lineGeometry.getCoordinates();

Note that the above is a very general example which follows the OP's code.

Ultimately, this might save others from having to roll their own WKT parser.

Nutiteq-Specific Code: In my case, I needed to draw a multiline string as a vector layer on a Nutiteq map. I realize the OP was asking about the google map android API, however in case any reader is also using Nutiteq (or if this algorithm is relevant for other map APIs), this is the nutiteq specific code:

geomLayer.clear(); // clear the old vector dataProjectionprojection= geomLayer.getProjection(); // Map's projection type// Iterate through the individual lines of our multi-line geometryfor(intlineIndex=0; lineIndex < geometry.getNumGeometries(); lineIndex++){
    GeometrylineGeometry= geometry.getGeometryN(lineIndex);
    ArrayList<MapPos> linePositions = newArrayList<MapPos>(lineGeometry.getCoordinates().length);

    // Iterate through this line's coordinatesfor(Coordinate coordinate : lineGeometry.getCoordinates()){
        // My server returns coordinates in WGS84/EPSG:4326 projection while the map// uses EPSG3857, so it is necessary to convert before adding to the// array list.MapPoslinePosition=newMapPos(projection.fromWgs84(coordinate.x, coordinate.y));
        linePositions.add(linePosition);
    }

    // Finally, add the line data to the vector layerLineline=newLine(linePositions, newDefaultLabel("some label"), lineStyle), null);
    geomLayer.add(line);
}

Note that the lineStyleSet and geomLayer are created previously in the activity's onCreate and can be researched here. The geomLayer is simple; here is my lineStyleSet:

Baca Juga

Note about lineStyle, it was created previously and is saved as an instance variable, like so:

BitmaplineMarker= UnscaledBitmapLoader.decodeResource(getResources(), R.drawable.line);

this.lineStyleSet = newStyleSet<LineStyle>();
LineStylelineStyle= LineStyle.builder().setLineJoinMode(LineStyle.NO_LINEJOIN).setWidth(0.2f).setColor(Color.RED).setBitmap(lineMarker).build();
lineStyleSet.setZoomStyle(minZoom, lineStyle);

Solution 3:

A WKT (well-known-text) file describes an ISO 19107 Geometry. Personally I try to avoid re-inventing the wheel, or "mess" with them in self written parsers ( you never know, whether your function covers all situation just because it worked once).

So here's another nice looking open source API, with examples, tutorials:

http://docs.geotools.org/

And here the WKTParser class

http://docs.geotools.org/stable/javadocs/org/geotools/geometry/text/WKTParser.html

Android Studio: Simply add this to your app build.gradle file:

dependencies {
    /* your other dependencies */
    compile 'org.opengis:geoapi:3.0.0'
}

Solution 4:

Here is a function I wrote to convert a simple (no holes etc.) polygon given in WKT into an array of LatLang:

publicstaticLatLng[] GetPolygonPoints(String poligonWkt){
    ArrayList<LatLng> points = new ArrayList<LatLng>();
    Pattern p =Pattern.compile("(\\d*\\.\\d+)\\s(\\d*\\.\\d+)");
    Matcher m = p.matcher(poligonWkt);
    String point;

    while (m.find()){
        point =  poligonWkt.substring(m.start(), m.end());
        points.add(new LatLng(Double.parseDouble(m.group(2)), Double.parseDouble(m.group(1))));
    }
    return points.toArray(new LatLng[points.size()]);
}

You can then use the array to add the polygon on the map:

LatLng[] points = GeographyHelper.GetPolygonPoints(shapeWkt);

Polygon p = mMap.addPolygon(
   new PolygonOptions()
      .add(points)
      .strokeWidth(4)
      .strokeColor(Color.RED));

Solution 5:

Just to expand on Paul's answer, since his answer helped me so much...

privatevoidsetUpMap(SomeObjectWithLocationAsWKT r) {

    List<LatLng> points = newArrayList<LatLng>();
    WKTReaderwktReader=newWKTReader();
    LineStringline=null;
    CoordinatelineCentroid=null;
    Coordinate[] lineCoordinates = null;

    // if our object's WKT geometry is not null - map itif (r.geowkt != null) {

        // use the JTS (Java Topology Suite) WKTReader to read that WKT!try {
            line = (LineString) wktReader.read(r.geowkt);
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        // using (JTS) again to getCoordinates of the linestring
        lineCoordinates = line.getCoordinates();

        // Iterate through the line's coordinates & assign to List<LatLng> pointsfor(Coordinate coordinate : lineCoordinates){
            points.add(newLatLng(coordinate.x, coordinate.y));
        }

        // add Polyline to Google MapPolylinep= mMap.addPolyline(
        newPolylineOptions()
        .addAll(points)
        .width(4)
        .color(Color.RED));
    }
}

// an example of zooming to the centroid of the WKT geometry // again, using (JTS - Java Topology Suite)privatevoidhandleNewLocation(Location location) {
    LatLnglatLng=null; 
    WKTReaderwktReader=newWKTReader();
    LineStringline=null;
    CoordinatelineCentroid=null; 

    // if our object's WKT geometry is not null - zoom to itif (r.geowkt != null) {
        try {
            line = (LineString) wktReader.read(r.geowkt);
            lineCentroid = line.getCentroid().getCoordinate();
            latLng = newLatLng(lineCentroid.x, lineCentroid.y);
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    } else {
        // just default to whatever location was passed in
        Log.d(TAG, location.toString());
        doublecurrentLatitude= location.getLatitude();
        doublecurrentLongitude= location.getLongitude();
        latLng = newLatLng(currentLatitude, currentLongitude);
    }
    CameraUpdateyourLocation= CameraUpdateFactory.newLatLngZoom(latLng, 19);
    mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
    mMap.animateCamera(yourLocation);
}

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