我对 Java 比较陌生，并且使用适用于 Android 的 ArcGIS Runtime SDK。我正在制作一个应用程序，用户可以在其中从微调器列表中选择包裹 ID。如果用户单击“ZOOM”按钮，则地图应缩放至所选地块。这是我的代码：
package gist8010.main;
import java.util.ArrayList;
import android.app.Activity;
import android.os.Bundle;
import android.os.StrictMode;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import com.esri.android.map.MapView;
import com.esri.android.map.ags.ArcGISDynamicMapServiceLayer;
import com.esri.android.map.ags.ArcGISTiledMapServiceLayer;
import com.esri.core.geometry.Envelope;
import com.esri.core.geometry.Point;
import com.esri.core.map.Feature;
import com.esri.core.map.FeatureResult;
import com.esri.core.tasks.query.QueryParameters;
import com.esri.core.tasks.query.QueryTask;
public class Spinner_WalkActivity extends Activity {
MapView mMapView;
Button mBtnZoom;
ArcGISDynamicMapServiceLayer mDynamicLayer;
Spinner mSpnParcels;
String mMapServiceURL = "http://indy14.athena.bcit.ca:8080/"
+ "esri_rest/services/gist_8010_test_ms/MapServer";
int mLotLayerID = 0;
String mLotLayerURL = mMapServiceURL + "/" + mLotLayerID;
String mLotNumColName = "PARCELS_ID";
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
/** Allow querying on main thread */
if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new
StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
}
/** Create spinner and button */
setMapView();
this.mBtnZoom = (Button) findViewById(R.id.btnZoom);
mBtnZoom.setOnClickListener(new OnClickListener() {
/** Upon click of zoom button, invoke th zoomtoFeature Method */
public void onClick(View v) {
zoomToFeature(v);
}
});
this.mSpnParcels = (Spinner) findViewById(R.id.spnParcels);
/** Add Layer to map */
mDynamicLayer = new ArcGISDynamicMapServiceLayer(mMapServiceURL);
mMapView.addLayer(mDynamicLayer);
QueryParameters qryLotNums = new QueryParameters();
qryLotNums.setReturnGeometry(false);
qryLotNums.setOutFields(new String[] { mLotNumColName });
qryLotNums.setWhere(mLotNumColName + ">0");
com.esri.core.tasks.query.QueryTask qtask = new com.esri.core.tasks.query.QueryTask(
mLotLayerURL);
try {
FeatureResult fSet = qtask.execute(qryLotNums);
ArrayList<String> listOfLotsNums = new ArrayList<String>();
Feature tmpFeat;
for (Object featAsObj : fSet) {
tmpFeat = (Feature) featAsObj;
listOfLotsNums.add(tmpFeat.getAttributeValue(mLotNumColName)
.toString());
}
ArrayAdapter<String> adtTmp = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_dropdown_item,
listOfLotsNums);
mSpnParcels.setAdapter(adtTmp);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}// of catch
}
@Override
protected void onDestroy() {
super.onDestroy();
}
@Override
protected void onPause() {
super.onPause();
mMapView.pause();
}
@Override
protected void onResume() {
super.onResume();
mMapView.unpause();
}
// =============================================================================
// Zooms the map the the MBR of the feature selected in the spinner
// import android.view.View;
// =============================================================================
public void zoomToFeature(View v) {
QueryParameters zoomQuery = new QueryParameters();
zoomQuery.setReturnGeometry(true);
zoomQuery.setOutFields(new String[] { mLotNumColName });
zoomQuery.setWhere(mLotNumColName + "=" + mSpnParcels.getSelectedItem());
QueryTask qtask = new QueryTask(mLotLayerURL);
try {
FeatureResult fset = qtask.execute(zoomQuery);
Feature tmpFeat = (Feature) fset.iterator().next();
Envelope envelope = new Envelope();
envelope.queryEnvelope((Envelope) tmpFeat.getGeometry());
getMapView().setExtent(envelope);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
// =============================================================================
// getter for the main map
// =============================================================================
private MapView getMapView() {
// =============================================================================
// if MapView is underlined in red, change the name to match your
// MapView
// =============================================================================
return mMapView;
}
// =============================================================================
// setter for the main map
// =============================================================================
private void setMapView() {
// ========================================================================
// if mapView is underlined in red then sync class-level var names
// if R.id.map is underlined in red ensure that you added the xml
// fragment
// such as "MapView Generic" to a layout
// ========================================================================
mMapView = (MapView) findViewById(R.id.map);
}
}
尝试调试后，我认为我的问题与 Envelope 类有关。queryEnvelope 方法接受一个 Envelope 参数。如您所见，我将 Feature tmpFeat 的几何图形从几何类型转换为 Envelope 类型。
当我在手机上运行该应用程序时，我的日志 Cat 中出现 System.Err 说：
java.lang.ClassCastException：com.esri.core.geometry.Polygon 无法转换为 com.esri.core.geometry.Envelope
我做错了吗？我想不出另一种方法将我的 Envelope 实例与我想要缩放到的要素类的几何图形联系起来。