Xamarin使用教程十三：在iOS项目中使用ArcGIS Server云端数据-控件新闻-慧都网

Xamarin使用教程十三：在iOS项目中使用ArcGIS Server云端数据

转帖|使用教程|编辑：我只采一朵|2014-09-03 09:35:39.000|阅读 1084 次

概述：本文介绍如何在 Xamarin.iOS 项目中使用 ArcGIS Server 云端专题数据

1. 添加专题服务数据

添加专题服务图层是非常简单的，只要初始化一个图层实例并把它添加到地图上就可以了，要初始化一个图层，你需要知道专题服务的 URL 和访问服务所需的用户凭据，而本文中使用专题服务是公开的，因此不需要任何凭据。将图层添加到地图上之后，你需要使用自定义符号将图层的数据在地图上显示成蓝色的小圆点。

public override void ViewDidLoad() {
    base.ViewDidLoad();
    // 添加地图底图
    var url = NSUrl.FromString("//services.arcgisonline.com/ArcGIS/rest/services/Canvas/World_Light_Gray_Base/MapServer");
    var tiledLayer = AGSTiledMapServiceLayer.TiledMapServiceLayerWithURL(url);
    this.MapView.AddMapLayer(tiledLayer, "Basemap Tiled Layer");
 
    // 专题图层
    var featureLayerUrl = NSUrl.FromString("//services.arcgis.com/oKgs2tbjK6zwTdvi/arcgis/rest/services/Major_World_Cities/FeatureServer/0");
    var featureLayer = AGSFeatureLayer.FeatureServiceLayerWithURL(featureLayerUrl, AGSFeatureLayerMode.OnDemand);
    featureLayer.OutFields = new string[] { "*" };
    this.MapView.AddMapLayer(featureLayer, "CloudData");
 
    // 自定义符号
    AGSSimpleMarkerSymbol featureSymbol = AGSSimpleMarkerSymbol.SimpleMarkerSymbolWithColor(UIColor.FromRGBA(0f, 0.46f, 0.68f, 1f));
    featureSymbol.Size = new SizeF(7, 7);
    featureSymbol.Style = AGSSimpleMarkerSymbolStyle.Circle;
    //featureSymbol.Outline
    featureLayer.Renderer = AGSSimpleRenderer.SimpleRendererWithSymbol(featureSymbol);
}

2. 允许用户选择专题

在这一节中，允许用户从列表中选择一个国家。要完成这个功能，需要在界面上添加一个按钮，并将按钮的 Touch Up Inside 事件连接到方法 ShowCountryPicker :

当用户点击按钮时，会调用 View Controller 的 ShowCountryPicker 方法，在这个方法中，我们初始化一个 UIPickerView 并把它显示在屏幕上，要显示国家列表，则需要指定数据源并实现 UIPickerViewDataSource 协议中定义的方法，为了能收到用户选择的选项，还需要实现 UIPickerViewDelegate 协议中定义的 pickerView:didSelectRow:inComponent: 方法。

partial void ShowCountryPicker(UIButton sender) {
    if (this.Countries == null) {
        this.Countries = new string[] { @"None",@"US",@"Canada",@"France",@"Australia",@"Brazil" };
    }
 
    var pickerSheet = new UIActionSheet(new RectangleF(0, 0, 320, 410));
    pickerSheet.ShowInView(this.View);
    pickerSheet.Bounds = new RectangleF(0, 0, 320, 410);
 
    var countryPicker = new UIPickerView(pickerSheet.Bounds);
    countryPicker.WeakDelegate = this;
    countryPicker.DataSource = this;
    countryPicker.ShowSelectionIndicator = true;
 
    pickerSheet.AddSubview(countryPicker);
}
 
#region "UIPickerview DataSource Part"
[Export("numberOfComponentsInPickerView:")]
public int GetComponentCount(UIPickerView picker) {
    return 1;
}
 
[Export("pickerView:numberOfRowsInComponent:")]
public virtual int GetRowsInComponent(UIPickerView picker, int component) {
    return this.Countries.Length;
}
 
[Export("pickerView:titleForRow:forComponent:")]
public virtual string GetTitle(UIPickerView picker, int row, int component) {
    return this.Countries[row];
}
#endregion
 
#region "UIPickerview Delegate Part"
[Export("pickerView:didSelectRow:inComponent:")]
public virtual void Selected(UIPickerView picker, int row, int component) {
 
    // Dismiss action sheet
    var pickerSheet = (UIActionSheet)picker.Superview;
    pickerSheet.DismissWithClickedButtonIndex(0, true);
}
#endregion

3. 显示选中的专题数据

我们现在来完成高亮显示属于用户选择的国家的数据。

首先得到的是用户选择的国家，如果用户选择了 None 的话，清空专题图层选中的数据；否则，使用类似于 SQL 的语法 COUNTRY = <selected_country> 来选中专题图层的数据。不过在进行选中操作之前，需要设置专题图层选中数据的符号，比如设置选中的数据在地图上显示为红色的原点；同时还需要设置图层的 queryDelegate ，实现 AGSFeatureLayerQueryDelegate 协议定义的方法，这样当选择操作完成时，才能收到通知。

#region "UIPickerview Delegate Part"
[Export("pickerView:didSelectRow:inComponent:")]
public virtual void Selected(UIPickerView picker, int row, int component) {
    var countryName = this.Countries[row];
    var featureLayer = (AGSFeatureLayer)this.MapView.MapLayerForName("CloudData");
 
    if (featureLayer.SelectionSymbol == null) {
        // SYMBOLOGY FOR WHERE CLAUSE SELECTION
        var selectedFeatureSymbol = AGSSimpleMarkerSymbol.SimpleMarkerSymbolWithColor(UIColor.FromRGBA(0.78f, 0.3f, 0.19f, 1f));
        selectedFeatureSymbol.Style = AGSSimpleMarkerSymbolStyle.Circle;
        selectedFeatureSymbol.Size = new SizeF(10, 10);
        featureLayer.SelectionSymbol = selectedFeatureSymbol;
    }
 
    if (featureLayer.WeakQueryDelegate == null) {
        featureLayer.WeakQueryDelegate = this;
    }
 
    if (countryName == "None") {
        // CLEAR SELECTION
        featureLayer.ClearSelection();
    }
    else {
        var selectQuery = AGSQuery.Query();
        selectQuery.Where = string.Format("COUNTRY = '{0}'", countryName);
        featureLayer.SelectFeaturesWithQuery(selectQuery, AGSFeatureLayerSelectionMethod.New);
    }
 
    // Dismiss action sheet
    var pickerSheet = (UIActionSheet)picker.Superview;
    pickerSheet.DismissWithClickedButtonIndex(0, true);
}
#endregion
 
#region "AGSFeature Query Delegate part"
[Export("featureLayer:operation:didSelectFeaturesWithFeatureSet:")]
public virtual void DidSelectFeaturesWithFeatureSet(AGSFeatureLayer featureLayer, NSOperation op, AGSFeatureSet featureSet) {
    AGSMutableEnvelope env = null;
    foreach (var selectedFature in featureSet.Features) {
        if (env != null) {
            env.UnionWithEnvelope(selectedFature.Geometry.Envelope);
        }
        else {
            env = (AGSMutableEnvelope)selectedFature.Geometry.Envelope.MutableCopy();
        }
    }
    this.MapView.ZoomToGeometry(env, 20, true);
}
#endregion