是否可以在OpenLayers中创建两个图层(其中一个是半透明的)并单独移动它们?如果是这样,怎么样?
我想让用户选择要移动的图层,或者如果不可能,请通过我自己的JavaScript代码移动一个图层,而另一个图层由用户控制.
两者都将是预渲染的pixmap图层,如果这很重要的话.
解决方法:
这是我提出的解决方案.它不漂亮,但它适用于我的目的.
更好的替代品非常受欢迎……
/**
* @requires OpenLayers/Layer/TMS.js
*/
MyLayer = OpenLayers.Class(OpenLayers.Layer.TMS, {
latShift: 0.0,
latShiftPx: 0,
setMap: function(map) {
OpenLayers.Layer.TMS.prototype.setMap.apply(this, arguments);
map.events.register("moveend", this, this.mapMoveEvent)
},
// This is the function you will want to modify for your needs
mapMoveEvent: function(event) {
var resolution = this.map.getResolution();
var center = this.map.getCenter();
// This is some calculation I use, replace it whatever you like:
var h = center.clone().transform(projmerc, proj4326);
var elliptical = EllipticalMercator.fromLonLat(h.lon, h.lat);
var myCenter = new OpenLayers.LonLat(elliptical.x, elliptical.y);
this.latShift = myCenter.lat - center.lat;
this.latShiftPx = Math.round(this.latShift/resolution);
this.div.style.top = this.latShiftPx + "px";
},
moveto: function(bounds, zoomChanged, dragging) {
bounds = bounds.add(0, this.latShift);
OpenLayers.Layer.TMS.prototype.moveto.apply(this, [bounds, zoomChanged, dragging]);
},
// mostly copied and pasted from Grid.js ...
moveGriddedTiles: function() {
var buffer = this.buffer + 1;
while(true) {
var tlTile = this.grid[0][0];
var tlViewPort = {
x: tlTile.position.x +
this.map.layerContainerOriginPx.x,
y: tlTile.position.y +
this.map.layerContainerOriginPx.y + this.latShiftPx // ... except this line
};
var ratio = this.getServerResolution() / this.map.getResolution();
var tileSize = {
w: Math.round(this.tileSize.w * ratio),
h: Math.round(this.tileSize.h * ratio)
};
if (tlViewPort.x > -tileSize.w * (buffer - 1)) {
this.shiftColumn(true, tileSize);
} else if (tlViewPort.x < -tileSize.w * buffer) {
this.shiftColumn(false, tileSize);
} else if (tlViewPort.y > -tileSize.h * (buffer - 1)) {
this.shiftRow(true, tileSize);
} else if (tlViewPort.y < -tileSize.h * buffer) {
this.shiftRow(false, tileSize);
} else {
break;
}
}
},
CLASS_NAME: "MyLayer"
});
请注意,这仅适用于OpenLayers 2.13或更高版本
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