本文基于腾讯课堂老胡的课《跟我学Openlayers--基础实例详解》做的学习笔记，使用的openlayers 5.3.x api。
源码 见 1085.html ，对应的 官网示例 https://openlayers.org/en/latest/examples/feature-move-animation.html?q=animation
image.png
核心技术点：
通过frameState.time和speed计算得到当前点位的index
根据index渲染对应的feature
image.png
<!DOCTYPE html>
<html>
<head>
<title>路径回放</title>
<link rel="stylesheet" href="../include/ol.css" type="text/css" />
<script src="../include/ol.js"></script>
</head>
<style></style>
<body>
<label for="speed">
速度:
<input id="speed" type="range" min="10" max="999" step="10" value="60">
</label>
<button id="start-animation">开始移动</button>
<div id="map" class="map"></div>
<div id="info"> </div>
<script>
var polyline = [
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'Ngn@{PmhEwaA{SeF_u@kQuyAw]wQeEgtAsZ}LiCarAkVwI}D??_}RcjEinPspDwSqCgs@',
'sPua@_OkXaMeT_Nwk@ob@gV}TiYs[uTwXoNmT{Uyb@wNg]{Nqa@oDgNeJu_@_G}YsFw]k',
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'~@ym@yjA??a@cFd@kBrCgDbAUnAcBhAyAdk@et@??kF}D??OL'
].join('');
var route = (new ol.format.Polyline({
factor: 1e6
}).readGeometry(polyline, {
dataProjection: 'EPSG:4326',
featureProjection: 'EPSG:3857'
}));
console.dir(route)
//获取轨迹上的所有点坐标
var routeCoords = route.getCoordinates();
var routeLength = routeCoords.length;
console.log('routeLength = '+routeLength) //routeLength = 542
var routeFeature = new ol.Feature({
type: 'route',
geometry: route
});
var geoMarker = new ol.Feature({
type: 'geoMarker',
geometry: new ol.geom.Point(routeCoords[0])
});
var startMarker = new ol.Feature({
type: 'icon',
geometry: new ol.geom.Point(routeCoords[0])
});
var endMarker = new ol.Feature({
type: 'icon',
geometry: new ol.geom.Point(routeCoords[routeLength - 1])
});
var styles = {
'route': new ol.style.Style({
stroke: new ol.style.Stroke({
width: 6, color: [237, 212, 0, 0.8]
})
}),
'icon': new ol.style.Style({
image: new ol.style.Icon({
anchor: [0.5, 1],
src: '../data/icon.png'
})
}),
'geoMarker': new ol.style.Style({
image: new ol.style.Circle({
radius: 7,
fill: new ol.style.Fill({ color: 'black' }),
stroke: new ol.style.Stroke({
color: 'white', width: 2
})
})
})
};
var animating = false; //标记当时是否执行动画
var speed, now;
var speedInput = document.getElementById('speed');
var startButton = document.getElementById('start-animation');
var vectorLayer = new ol.layer.Vector({
source: new ol.source.Vector({
features: [routeFeature, geoMarker, startMarker, endMarker]
}),
style: function (feature) {
if (animating && feature.get('type') === 'geoMarker') {
return null;
}
return styles[feature.get('type')];
}
});
var center = [-5639523.95, -3501274.52];
var map = new ol.Map({
target: document.getElementById('map'),
loadTilesWhileAnimating: true,
view: new ol.View({
center: center,
zoom: 10,
minZoom: 2,
maxZoom: 19
}),
layers: [
new ol.layer.Tile({
source: new ol.source.BingMaps({
imagerySet: 'AerialWithLabels',
key: 'As1HiMj1PvLPlqc_gtM7AqZfBL8ZL3VrjaS3zIb22Uvb9WKhuJObROC-qUpa81U5'
})
}),
vectorLayer
]
});
var moveFeature = function (event) {
var vectorContext = event.vectorContext;
var frameState = event.frameState;
if (animating) {
var elapsedTime = frameState.time - now; //获取动画已经执行的时间
var index = Math.round(speed * elapsedTime / 1000); //获取到当前应画到的点的索引,index = (当前选中速度 * 已经执行的时间 / 最大速度值)
console.log(' 已经动画时间 = '+elapsedTime) //
console.log(' 当前index = '+index +' ,speed = '+speed) //
if (index >= routeLength) {
stopAnimation(true); //动画结束条件
return;
}
var currentPoint = new ol.geom.Point(routeCoords[index]);
var feature = new ol.Feature(currentPoint);
vectorContext.drawFeature(feature, styles.geoMarker);
}
map.render();//执行此函数时，又会触发postcompose事件；触发postcompose事件后，会执行函数moveFeature
};
function startAnimation() {
if (animating) {
stopAnimation(false);
} else {
animating = true;
now = new Date().getTime();
speed = speedInput.value;
startButton.textContent = '停止移动';
geoMarker.setStyle(null);//把动画的样式先隐藏，一会为了让它有动画的效果
map.getView().setCenter(center);
map.on('postcompose', moveFeature);
map.render();
}
}
//若动画结束为终点，则把移动点设置到终点；否则把移动点设置到起点。
function stopAnimation(ended) {
animating = false;
startButton.textContent = '开始移动';
var coord = ended ? routeCoords[routeLength - 1] : routeCoords[0];
geoMarker.getGeometry().setCoordinates(coord);
map.un('postcompose', moveFeature);
}
startButton.addEventListener('click', startAnimation, false);
</script>
</body>
</html>
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