arcgis runtime100（十一、十二课时）
第十一、十二课时查询
Identify methods are asynchronous, so that the UI thread of your application is not blocked waiting for results.
识别方法都是异步方法，不会阻塞UI进程
识别元素
在一个元素图层里查询元素
- 得到点击点
MyMapView.GeoViewTapped += async (s, e) =>
{
// get the tap location in screen units
System.Windows.Point tapScreenPoint = e.Position;
// ... code here to identify using the tap point ...
};
- 调取识别方法
- 选择一个图层
- 选择一个屏幕识别半径
- 选择是否包含弹出窗口
- 选择返回数量
var layer = MyMapView.Map.OperationalLayers[0];
var pixelTolerance = 20;
var returnPopupsOnly = false;
var maxResults = 5;
IdentifyLayerResult idResults = await MyMapView.IdentifyLayerAsync(layer, tapScreenPoint, pixelTolerance, returnPopupsOnly, maxResults);
- 迭代结果
FeatureLayer idLayer = idResults.LayerContent as FeatureLayer;
foreach (GeoElement idElement in idResults.GeoElements)
{
Feature idFeature = idElement as Feature;
idLayer.SelectFeature(idFeature);
}
在所有元素图层中查找元素
// get the tap location in screen units
System.Windows.Point tapScreenPoint = e.Position;
//查看此处不同
var pixelTolerance = 20;
var returnPopupsOnly = false;
var maxLayerResults = 5;
// 此处是关键
IReadOnlyList<IdentifyLayerResult> idLayerResults = await MyMapView.IdentifyLayersAsync(tapScreenPoint, pixelTolerance, returnPopupsOnly, maxLayerResults);
// iterate the results for each layer
foreach (IdentifyLayerResult idResults in idLayerResults)
{
// get the layer identified and cast it to FeatureLayer
FeatureLayer idLayer = idResults.LayerContent as FeatureLayer;
// iterate each identified GeoElement in the results for this layer
foreach (GeoElement idElement in idResults.GeoElements)
{
// cast the result GeoElement to Feature
Feature idFeature = idElement as Feature;
// select this feature in the feature layer
idLayer.SelectFeature(idFeature);
}
}
只识别最顶层项
// get the tap location in screen units
System.Windows.Point tapScreenPoint = e.Position;
var pixelTolerance = 20;
var returnPopupsOnly = false;
// identify the topmost feature for all layers, passing in the tap point, tolerance, and types to return
IReadOnlyList<IdentifyLayerResult> idLayerResults = await MyMapView.IdentifyLayersAsync(tapScreenPoint, pixelTolerance, returnPopupsOnly);
// iterate the results for each layer
foreach (IdentifyLayerResult idResults in idLayerResults)
{
// get the layer identified and cast it to FeatureLayer
FeatureLayer idLayer = idResults.LayerContent as FeatureLayer;
// see if a result was found for this layer (will be 0 or 1 result for each layer)
if (idResults.GeoElements.Count == 1)
{
// cast the result GeoElement to Feature
Feature idFeature = idResults.GeoElements[0] as Feature;
// select this feature in the feature layer
idLayer.SelectFeature(idFeature);
}
}
在image layer上做识别
private void ProcessIdentifyResults(IReadOnlyList<IdentifyLayerResult> idLayerResults)
{
// iterate the results for each layer
foreach (IdentifyLayerResult idResults in idLayerResults)
{
// get the layer identified and try to cast it to FeatureLayer
FeatureLayer featLayer = idResults.LayerContent as FeatureLayer;
// process feature layer results
if (featLayer != null)
{
// iterate each identified GeoElement in the results for this layer
foreach (GeoElement idElement in idResults.GeoElements)
{
// cast the result GeoElement to Feature
Feature idFeature = idElement as Feature;
// select this feature in the feature layer
featLayer.SelectFeature(idFeature);
}
}
// if not a feature layer, check for map image layer
if (idResults.LayerContent is ArcGISMapImageLayer || idResults.LayerContent is ArcGISMapImageSublayer)
{
// iterate each identified GeoElement in the results
foreach (GeoElement idElement in idResults.GeoElements)
{
// cast the result GeoElement to Feature
Feature idFeature = idElement as Feature;
// can get the geometry and attributes, but FeatureTable will be null
Geometry featureShape = idFeature.Geometry;
IDictionary<string, object> featureAttrs = idFeature.Attributes;
// ... code to display the GeoElement attributes here ...
}
// see if there are sublayer results, call this function again and pass them in
ProcessIdentifyResults(idResults.SublayerResults);
}
}
}
返回弹出框
// identify all layers in the MapView, passing the tap point, tolerance, types to return, and max results
IReadOnlyList<IdentifyLayerResult> idLayerResults = await MyMapView.IdentifyLayersAsync(tapScreenPoint, pixelTolerance, returnPopupsOnly, maxLayerResults);
if (idLayerResults.Count > 0)
{
// get the first identify result
IdentifyLayerResult firstIdLayerResult = idLayerResults.FirstOrDefault();
if (firstIdLayerResult.Popups.Count > 0)
{
// get the first popup from the result
Popup firstPopup = firstIdLayerResult.Popups.FirstOrDefault();
// ... code here to show popup ...
}
}
在WMS layer上做识别
// Perform the identify operation on the WMS layer
IdentifyLayerResult myIdentifyResult = await MyMapView.IdentifyLayerAsync(myWmsLayer, e.Position, 20, false);
// Return if there's no feature to show
if (myIdentifyResult.GeoElements.Count() < 1) { return; }
// Retrieve the identified feature, which is always a WmsFeature for WMS layers
WmsFeature identifiedFeature = (WmsFeature)myIdentifyResult.GeoElements[0];
// WMS图层只有HTML属性，并且没有geometry属性
string htmlContent = identifiedFeature.Attributes["HTML"].ToString();
识别graphics
// identify all graphics overlays in the MapView, passing the tap point, tolerance, types to return, and max results
IReadOnlyList<IdentifyGraphicsOverlayResult> idGraphicOverlayResults = await MyMapView.IdentifyGraphicsOverlaysAsync(tapScreenPoint, pixelTolerance, returnPopupsOnly, maxLayerResults);
// iterate each graphics overlay
foreach(IdentifyGraphicsOverlayResult idGraphicResult in idGraphicOverlayResults)
{
// iterate all graphics in the overlay and select them
foreach(Graphic g in idGraphicResult.Graphics)
{
g.IsSelected = true;
}
}
识别关系元素
示例 data/FeatureLayerQuery
示例data中的三种加载方式
