在下面的源码中我主要有几点不明白 请各位大神能够帮助解答
第一、这个个例子中是什么时候开始对地图进行初始化的啊？ 在xml文件中的url="http://www.arcgis.com/home/webmap/viewer.html?webmap=58e58acce685442aa4c73f91fbb3a387"这句话是对该地图进行初始化吗？ 为什么不是一个mapserver啊？
代码片段，双击复制
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/map" android:layout_width="fill_parent"
android:layout_height="fill_parent"
url="http://www.arcgis.com/home/webmap/viewer.html?webmap=58e58acce685442aa4c73f91fbb3a387"
>
第二 、对于代码中的以下部分不明白
if (source == mv && status == STATUS.INITIALIZED) {
gl = new GraphicsLayer();
SimpleRenderer sr = new SimpleRenderer(
new SimpleFillSymbol(Color.RED));
gl.setRenderer(sr);//设置渲染图形层
mv.addLayer(gl);
boolean doQuery = false;
for (Layer lv : mv.getLayers()) {
if (lv instanceof ArcGISTiledMapServiceLayer) {
ArcGISTiledMapServiceLayer tLayer = (ArcGISTiledMapServiceLayer) lv;
if (tLayer.getUrl().equals(targetServerURL)) {
doQuery = true;
break;
}
}
}
那个for循环中的的代码是用来干什么的啊？
以下是程序源码
package com.esri.arcgis.android.samples.querytask;
import android.app.Activity;
import android.app.ProgressDialog;
import android.graphics.Color;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import com.esri.android.map.GraphicsLayer;
import com.esri.android.map.Layer;
import com.esri.android.map.MapView;
import com.esri.android.map.ags.ArcGISTiledMapServiceLayer;
import com.esri.android.map.event.OnStatusChangedListener;
import com.esri.arcgis.android.samples.attributequery.R;
import com.esri.core.geometry.Envelope;
import com.esri.core.geometry.SpatialReference;
import com.esri.core.map.FeatureSet;
import com.esri.core.map.Graphic;
import com.esri.core.renderer.SimpleRenderer;
import com.esri.core.symbol.SimpleFillSymbol;
import com.esri.core.tasks.ags.query.Query;
import com.esri.core.tasks.ags.query.QueryTask;
public class AttributeQuery extends Activity {
/** Called when the activity is first created. */
MapView mv;
GraphicsLayer gl;
Graphic graphic;
Graphic fillGraphic;
Button querybt;
String targetServerURL = "http://services.arcgisonline.com/ArcGIS/rest/services/Demographics/USA_Average_Household_Size/MapServer";
boolean blQuery = true;
ProgressDialog progress;
final static int HAS_RESULTS = 1;
final static int NO_RESULT = 2;
final static int CLEAR_RESULT = 3;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mv = (MapView) findViewById(R.id.map);
mv.setOnStatusChangedListener(new OnStatusChangedListener() {
private static final long serialVersionUID = 1L;
public void onStatusChanged(Object source, STATUS status) {
if (source == mv && status == STATUS.INITIALIZED) {
gl = new GraphicsLayer();
SimpleRenderer sr = new SimpleRenderer(
new SimpleFillSymbol(Color.RED));
gl.setRenderer(sr);//设置渲染图形层
mv.addLayer(gl);
boolean doQuery = false;
for (Layer lv : mv.getLayers()) {
if (lv instanceof ArcGISTiledMapServiceLayer) {
ArcGISTiledMapServiceLayer tLayer = (ArcGISTiledMapServiceLayer) lv;
if (tLayer.getUrl().equals(targetServerURL)) {
doQuery = true;
break;
}
}
}
if (!doQuery) {
Toast toast = Toast.makeText(AttributeQuery.this,
"URL for query does not exist any more",
Toast.LENGTH_LONG);
toast.show();
} else {
querybt.setEnabled(true);
}
}
}
});
querybt = (Button) findViewById(R.id.queryButton);
querybt.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
if (blQuery) {
String targetLayer = targetServerURL.concat("/3");
String[] queryParams = { targetLayer, "AVGHHSZ_CY>3.5" };
AsyncQueryTask ayncQuery = new AsyncQueryTask();
ayncQuery.execute(queryParams);
} else {
gl.removeAll();
blQuery = true;
querybt.setText("Average Household > 3.5");
}
}
});
}
/**
*
* Query Task executes asynchronously.
*
*/
private class AsyncQueryTask extends AsyncTask<String, Void, FeatureSet> {
protected void onPreExecute() {
progress = ProgressDialog.show(AttributeQuery.this, "",
"Please wait....query task is executing");
}
/**
* First member in parameter array is the query URL; second member is
* the where clause.
*/
protected FeatureSet doInBackground(String... queryParams) {
if (queryParams == null || queryParams.length <= 1)
return null;
String url = queryParams[0];
Query query = new Query();
String whereClause = queryParams[1];
SpatialReference sr = SpatialReference.create(102100);
query.setGeometry(new Envelope(-20147112.9593773, 557305.257274575,
-6569564.7196889, 11753184.6153385));
query.setOutSpatialReference(sr);
query.setReturnGeometry(true);
query.setWhere(whereClause);
QueryTask qTask = new QueryTask(url);
FeatureSet fs = null;
try {
fs = qTask.execute(query);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
return fs;
}
return fs;
}
protected void onPostExecute(FeatureSet result) {
String message = "No result comes back";
if (result != null) {
Graphic[] grs = result.getGraphics();
if (grs.length > 0) {
gl.addGraphics(grs);
message = (grs.length == 1 ? "1 result has " : Integer
.toString(grs.length) + " results have ")
+ "come back";
}
}
progress.dismiss();
Toast toast = Toast.makeText(AttributeQuery.this, message,
Toast.LENGTH_LONG);
toast.show();
querybt.setText("Clear graphics");
blQuery = false;
}
}
@Override
protected void onPause() {
super.onPause();
mv.pause();
}
@Override protected void onResume() {
super.onResume();
mv.unpause();
}
}
