[update] 优化graphic 点击选择计算不准确的问题

yuzhiyao · yuzhiyao · commit 7d054f1d172d · 2019-11-14T08:36:53.000+08:00
diff --git a/src/openlayers/overlay/Graphic.js b/src/openlayers/overlay/Graphic.js
@@ -151,6 +151,7 @@ export class Graphic extends ol.source.ImageCanvas {
          */
         function _forEachFeatureAtCoordinate(coordinate, resolution, callback, evtPixel, e) {
             let graphics = me.getGraphicsInExtent();
+            let includeGraphics  = []; // 点密集的时候，符合条件的有多个 还需精确计算
             for (let i = graphics.length - 1; i >= 0; i--) {
                 let style = graphics[i].getStyle();
                 if (!style) {
@@ -201,7 +202,8 @@ export class Graphic extends ol.source.ImageCanvas {
                     extent[1] = center[1] - image.getAnchor()[1] * resolution;
                     extent[3] = center[1] + image.getAnchor()[1] * resolution;
                     if (ol.extent.containsCoordinate(extent, coordinate)) {
-                        contain = true;
+                        includeGraphics.push(graphics[i]);
+                        // contain = true;
                     }
                 }
 
@@ -218,11 +220,60 @@ export class Graphic extends ol.source.ImageCanvas {
                     me._highLightClose();
                 }
             }
+            // 精确计算
+            let exactGraphic = this._getExactGraphic(includeGraphics, evtPixel);
+            if(exactGraphic){
+                let _style = exactGraphic.getStyle(),
+                _center = exactGraphic.getGeometry().getCoordinates(),
+                _image = new ol.style.Style({
+                    image: _style
+                }).getImage();
+
+                if (me.isHighLight) {
+                    me._highLight(_center, _image, exactGraphic, evtPixel);
+                }
+                if (callback) {
+                    callback(exactGraphic, e);
+                } 
+            }else{
+                if (me.isHighLight) {
+                    me._highLightClose();
+                }
+            }
             return undefined;
         }
 
     }
 
+    /**
+     * @private
+     * @function ol.source.Graphic.prototype._getExactGraphic
+     * @description 获取到精确的graphic。
+     * @param {Array.<ol.Graphic>}  graphics - 点要素对象数组。
+     * @param {ol.Pixel} evtPixel - 当前选中的屏幕像素坐标。
+     */
+    _getExactGraphic(graphics, evtPixel){
+        if(graphics.length === 0){
+            return false;
+        }else if(graphics.length === 1){
+            return graphics[0];
+        } else{
+            let distances = [];
+            graphics.map((graphic, index) =>{
+                let center = graphic.getGeometry().getCoordinates(),
+                centerPixel = this.map.getPixelFromCoordinate(center),
+                distance = Math.sqrt(Math.pow((centerPixel[0]-evtPixel[0]),2) + Math.pow((centerPixel[1]-evtPixel[1]),2));
+                distances.push({distance: distance, index: index});
+                return null; 
+            });
+
+            distances.sort( (a,b) =>{
+                return a.distance - b.distance
+            });
+            return graphics[distances[0].index];
+        }
+    }
+
     /**
      * @function ol.source.Graphic.prototype.setGraphics
      * @description 设置绘制的点要素，会覆盖之前的所有要素。
