原文链接及内容
通过切换上述下拉框的下拉选项，可以改变比例尺的单位及样式。
main.js代码如下：
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| import Map from 'ol/Map.js';
import OSM from 'ol/source/OSM.js';
import TileLayer from 'ol/layer/Tile.js';
import View from 'ol/View.js';
import {ScaleLine, defaults as defaultControls} from 'ol/control.js';
const scaleBarOptionsContainer = document.getElementById('scaleBarOptions');
const unitsSelect = document.getElementById('units');
const typeSelect = document.getElementById('type');
const stepsRange = document.getElementById('steps');
const scaleTextCheckbox = document.getElementById('showScaleText');
const invertColorsCheckbox = document.getElementById('invertColors');
let control;
function scaleControl() {
if (typeSelect.value === 'scaleline') {
control = new ScaleLine({
units: unitsSelect.value,
});
scaleBarOptionsContainer.style.display = 'none';
} else {
control = new ScaleLine({
units: unitsSelect.value,
bar: true,
steps: parseInt(stepsRange.value, 10),
text: scaleTextCheckbox.checked,
minWidth: 140,
});
onInvertColorsChange();
scaleBarOptionsContainer.style.display = 'block';
}
return control;
}
const map = new Map({
controls: defaultControls().extend([scaleControl()]),
layers: [
new TileLayer({
source: new OSM(),
}),
],
target: 'map',
view: new View({
center: [0, 0],
zoom: 2,
}),
});
function reconfigureScaleLine() {
map.removeControl(control);
map.addControl(scaleControl());
}
function onChangeUnit() {
control.setUnits(unitsSelect.value);
}
function onInvertColorsChange() {
control.element.classList.toggle(
'ol-scale-bar-inverted',
invertColorsCheckbox.checked
);
}
unitsSelect.addEventListener('change', onChangeUnit);
typeSelect.addEventListener('change', reconfigureScaleLine);
stepsRange.addEventListener('input', reconfigureScaleLine);
scaleTextCheckbox.addEventListener('change', reconfigureScaleLine);
invertColorsCheckbox.addEventListener('change', onInvertColorsChange);
|
界面布局文件index.html代码如下：
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| <!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Scale Line</title>
<link rel="stylesheet" href="node_modules/ol/ol.css">
<style>
.map {
width: 100%;
height: 400px;
}
#scaleBarOptions {
display: none;
}
input[type=range] {
vertical-align: middle;
}
.ol-scale-bar-inverted .ol-scale-singlebar-even {
background-color: var(--ol-background-color);
}
.ol-scale-bar-inverted .ol-scale-singlebar-odd {
background-color: var(--ol-subtle-foreground-color);
}
</style>
</head>
<body>
<div id="map" class="map"></div>
<label for="units">Units:</label>
<select id="units">
<option value="degrees">degrees</option>
<option value="imperial">imperial inch</option>
<option value="us">us inch</option>
<option value="nautical">nautical mile</option>
<option value="metric" selected>metric</option>
</select>
<label for="type">Type:</label>
<select id="type">
<option value="scaleline">ScaleLine</option>
<option value="scalebar">ScaleBar</option>
</select>
<div id="scaleBarOptions">
<label for="steps">Steps:</label>
<input id="steps" type="range" value="4" min="1" max="8">
<label><input type="checkbox" id="showScaleText" checked> Show scale text</label>
<label><input type="checkbox" id="invertColors"> Invert colors</label>
</div>
<script src="https://cdn.jsdelivr.net/npm/elm-pep@1.0.6/dist/elm-pep.js"></script>
<script type="module" src="main.js"></script>
</body>
</html>
|
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