Openlayers 6 - Show Geojson Label on line

问题

I am confused about how to put a label in GeoJSON file to show on the map. I've tried many of examples from openlayers.org but they won't work.

I want to show the text from properties "name" in my GeoJSON file on top of the map and along the line, like street name. Now only the line is displayed.

Here's my script.

<script type="text/javascript">

    var style = new ol.style.Style({
    text: new ol.style.Text({
    font: 'bold 11px "Open Sans", "Arial Unicode MS", "sans-serif"',
    placement: 'line',
    fill: new ol.style.Fill({
      color: 'white'
    })
    })
    });

    var format = new ol.format.GeoJSON({
    featureProjection:"EPSG:3857"
    });

    var allbussource = new ol.source.Vector({
    features:format.readFeatures(allbus)
    });

    var allbuslayer = new ol.layer.Vector({
    source: allbussource,
        style: new ol.style.Style({
        stroke: new ol.style.Stroke({
            color: 'red',
            width: 3
        }),
        }), function(feature) {
      style.getText().setText(feature.get('name'));
      return style;
    }
    });

    var allbusdashsource = new ol.source.Vector({
    features:format.readFeatures(allbusdash)
    });

    var allbusdashlayer = new ol.layer.Vector({
    source: allbusdashsource,
        style: new ol.style.Style({
        stroke: new ol.style.Stroke({
            color: 'red',
            width: 3,
            lineDash: [6, 10]
        })
    })
    });

    var allbuslayergroup = new ol.layer.Group({
    layers: [allbuslayer, allbusdashlayer]
    });

      var map = new ol.Map({
        target: 'map',
        layers: [
          new ol.layer.Tile({
            source: new ol.source.OSM({
            url: 'tiles/{z}/{x}/{y}.png',
            crossOrigin: null,
            })
          }), allbuslayergroup
        ],
        view: new ol.View({
          center: ol.proj.fromLonLat([100.568, 14.353]),
          zoom: 14,
          minZoom: 14,
          maxZoom: 19,
          extent: [11187608.82, 1608083.02, 11203003.55, 1621297.19],
          constrainResolution: true
        })
      });


    </script>

and here's an example of my GeoJSON file, I've converted to .js and included it in the HTML head.

var allbus = {
"type": "FeatureCollection",
"features": [
{ "type": "Feature", "properties": { "osm_id": "21946733", "name": "2400  2435" }, "geometry": { "type": "LineString", "coordinates": [ [ 100.5910608, 14.372016 ], [ 100.5908929, 14.3718848 ], [ 100.5902894, 14.3715546 ], [ 100.5901471, 14.3714576 ], [ 100.5900982, 14.3714101 ], [ 100.5899568, 14.371273 ], [ 100.5898938, 14.3711547 ], [ 100.5898514, 14.3710753 ], [ 100.5897955, 14.3707167 ], [ 100.589761, 14.3704954 ], [ 100.589738, 14.3702688 ], [ 100.5897387, 14.370049 ], [ 100.5898064, 14.3697453 ], [ 100.5899893, 14.3692589 ], [ 100.5901096, 14.3689535 ], [ 100.5903428, 14.3683034 ], [ 100.5904301, 14.3678864 ], [ 100.5904319, 14.3674561 ], [ 100.5904349, 14.3667348 ], [ 100.5904014, 14.3655408 ], [ 100.5903904, 14.3651487 ], [ 100.5903823, 14.3645017 ], [ 100.5905217, 14.3640963 ], [ 100.5909407, 14.3630018 ], [ 100.5913408, 14.3618161 ], [ 100.5913944, 14.3615798 ], [ 100.5913889, 14.3613111 ], [ 100.5913774, 14.3612627 ], [ 100.5913429, 14.3611183 ], [ 100.5911797, 14.3604346 ], [ 100.5908801, 14.3590742 ], [ 100.59081, 14.3587564 ], [ 100.5907702, 14.3585754 ], [ 100.5907349, 14.3580533 ], [ 100.590891, 14.3571796 ], [ 100.5910189, 14.35651 ], [ 100.5911179, 14.3559918 ] ] } },
{ "type": "Feature", "properties": { "osm_id": "23745845", "name": "101  1002*" }, "geometry": { "type": "LineString", "coordinates": [ [ 100.5530414, 14.3614133 ], [ 100.5530547, 14.3613011 ] ] } }
]
};

回答1:

Your allbuslayer setup should look something like this (you can change font and color as appropriate for your application)

var allbusstyle = new ol.style.Style({
    stroke: new ol.style.Stroke({
        color: 'red',
        width: 3
    }),
    text: new ol.style.Text({
        font: '12px Calibri,sans-serif',
        placement: 'line',
        fill: new ol.style.Fill({
            color: '#000'
        }),
        stroke: new ol.style.Stroke({
            color: '#fff',
            width: 3
        })
    })
});

var allbuslayer = new ol.layer.Vector({
    source: allbussource,
    style: function(feature) {
        allbusstyle.getText().setText(feature.get('name'));
        return allbusstyle;
    }
});

来源：https://stackoverflow.com/questions/59262927/openlayers-6-show-geojson-label-on-line