android - 如何使 ArcGIS API for android 中的 Identify 任务与标准 WMS 一起工作

Question

我想在 ARCGIS API for android 中使用 Identify Task。我使用了 this示例并且它工作正常但是当我尝试更改 URL 以从另一个 WMS 获取数据时它显示错误这是我的另一个wms我在以下行中收到错误

for (int index = 0; index < results.length; index++) {

            result_1 = results[index];
            String displayFieldName = result_1.getDisplayFieldName();
            Map<String, Object> attr = result_1.getAttributes();
            for (String key : attr.keySet()) {
                if (key.equalsIgnoreCase(displayFieldName)) {
                    resultList.add(result_1);
                }
            }
        }

在我从例子中得到的这个类中

    package com.esri.arcgis.android.samples.identifytask;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.Color;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.TextView;

import com.esri.android.action.IdentifyResultSpinner;
import com.esri.android.action.IdentifyResultSpinnerAdapter;
import com.esri.android.map.Callout;
import com.esri.android.map.MapView;
import com.esri.android.map.ags.ArcGISTiledMapServiceLayer;
import com.esri.android.map.event.OnSingleTapListener;
import com.esri.core.geometry.Envelope;
import com.esri.core.geometry.Point;
import com.esri.core.tasks.identify.IdentifyParameters;
import com.esri.core.tasks.identify.IdentifyResult;
import com.esri.core.tasks.identify.IdentifyTask;

/**
 * This sample allows the user to identify data based on single tap and view the
 * results in a callout window which has a spinner in its layout. Also the user
 * can select any of the results displayed and view its details. The details are
 * the attribute values.
 * 
 * The output value shown in the spinner is the display field.
 * 
 */

public class Identify extends Activity {

// create ArcGIS objects
MapView mMapView = null;
IdentifyParameters params = null;

// create UI objects
static ProgressDialog dialog;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    // Retrieve the map and initial extent from XML layout
    mMapView = (MapView) findViewById(R.id.map);

    // add demographic layer to the map
    mMapView.addLayer(new ArcGISTiledMapServiceLayer(this.getResources()
            .getString(R.string.identify_task_url_for_avghouseholdsize)));

    // set Identify Parameters
    params = new IdentifyParameters();
    params.setTolerance(20);
    params.setDPI(98);
    params.setLayers(new int[] { 4 });
    params.setLayerMode(IdentifyParameters.ALL_LAYERS);

    // Identify on single tap of map
    mMapView.setOnSingleTapListener(new OnSingleTapListener() {

        private static final long serialVersionUID = 1L;

        @Override
        public void onSingleTap(final float x, final float y) {

            if (!mMapView.isLoaded()) {
                return;
            }

            // Add to Identify Parameters based on tapped location
            Point identifyPoint = mMapView.toMapPoint(x, y);

            params.setGeometry(identifyPoint);
            params.setSpatialReference(mMapView.getSpatialReference());
            params.setMapHeight(mMapView.getHeight());
            params.setMapWidth(mMapView.getWidth());
            params.setReturnGeometry(false);

            // add the area of extent to identify parameters
            Envelope env = new Envelope();
            mMapView.getExtent().queryEnvelope(env);
            params.setMapExtent(env);

            // execute the identify task off UI thread
            MyIdentifyTask mTask = new MyIdentifyTask(identifyPoint);
            mTask.execute(params);
        }

    });

}

private ViewGroup createIdentifyContent(final List<IdentifyResult> results) {

    // create a new LinearLayout in application context
    LinearLayout layout = new LinearLayout(this);

    // view height and widthwrap content
    layout.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT,
            LayoutParams.WRAP_CONTENT));

    // default orientation
    layout.setOrientation(LinearLayout.HORIZONTAL);

    // Spinner to hold the results of an identify operation
    IdentifyResultSpinner spinner = new IdentifyResultSpinner(this, results);

    // make view clickable
    spinner.setClickable(false);
    spinner.canScrollHorizontally(BIND_ADJUST_WITH_ACTIVITY);

    // MyIdentifyAdapter creates a bridge between spinner and it's data
    MyIdentifyAdapter adapter = new MyIdentifyAdapter(this, results);
    spinner.setAdapter(adapter);
    spinner.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT,
            LayoutParams.WRAP_CONTENT));
    layout.addView(spinner);

    return layout;
}

/**
 * This class allows the user to customize the string shown in the callout.
 * By default its the display field name.
 * 
 * A spinner adapter defines two different views; one that shows the data in
 * the spinner itself and one that shows the data in the drop down list when
 * spinner is pressed.
 * 
 */
public class MyIdentifyAdapter extends IdentifyResultSpinnerAdapter {
    String m_show = null;
    List<IdentifyResult> resultList;
    int currentDataViewed = -1;
    Context m_context;

    public MyIdentifyAdapter(Context context, List<IdentifyResult> results) {
        super(context, results);
        this.resultList = results;
        this.m_context = context;
    }

    // Get a TextView that displays identify results in the callout.
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        String LSP = System.getProperty("line.separator");
        StringBuilder outputVal = new StringBuilder();

        // Resource Object to access the Resource fields
        Resources res = getResources();

        // Get Name attribute from identify results
        IdentifyResult curResult = this.resultList.get(position);

        if (curResult.getAttributes().containsKey(
                res.getString(R.string.NAME))) {
            outputVal.append("Place: "
                    + curResult.getAttributes()
                            .get(res.getString(R.string.NAME)).toString());
            outputVal.append(LSP);
        }

        if (curResult.getAttributes().containsKey(
                res.getString(R.string.ID))) {
            outputVal.append("State ID: "
                    + curResult.getAttributes()
                            .get(res.getString(R.string.ID)).toString());
            outputVal.append(LSP);
        }

        if (curResult.getAttributes().containsKey(
                res.getString(R.string.ST_ABBREV))) {
            outputVal.append("Abbreviation: "
                    + curResult.getAttributes()
                            .get(res.getString(R.string.ST_ABBREV))
                            .toString());
            outputVal.append(LSP);
        }

        if (curResult.getAttributes().containsKey(
                res.getString(R.string.TOTPOP_CY))) {
            outputVal.append("Population: "
                    + curResult.getAttributes()
                            .get(res.getString(R.string.TOTPOP_CY))
                            .toString());
            outputVal.append(LSP);

        }

        if (curResult.getAttributes().containsKey(
                res.getString(R.string.LANDAREA))) {
            outputVal.append("Area: "
                    + curResult.getAttributes()
                            .get(res.getString(R.string.LANDAREA))
                            .toString());
            outputVal.append(LSP);

        }

        // Create a TextView to write identify results
        TextView txtView;
        txtView = new TextView(this.m_context);
        txtView.setText(outputVal);
        txtView.setTextColor(Color.BLACK);
        txtView.setLayoutParams(new ListView.LayoutParams(
                LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT));
        txtView.setGravity(Gravity.CENTER_VERTICAL);

        return txtView;
    }
}

@Override
protected void onPause() {
    super.onPause();
    mMapView.pause();
}

@Override
protected void onResume() {
    super.onResume();
    mMapView.unpause();
}

private class MyIdentifyTask extends
        AsyncTask<IdentifyParameters, Void, IdentifyResult[]> {

    IdentifyTask task = new IdentifyTask(Identify.this.getResources()
            .getString(R.string.identify_task_url_for_avghouseholdsize));

    IdentifyResult[] M_Result;

    Point mAnchor;

    MyIdentifyTask(Point anchorPoint) {
        mAnchor = anchorPoint;
    }

    @Override
    protected void onPreExecute() {
        // create dialog while working off UI thread
        dialog = ProgressDialog.show(Identify.this, "Identify Task",
                "Identify query ...");

    }

    protected IdentifyResult[] doInBackground(IdentifyParameters... params) {

        // check that you have the identify parameters
        if (params != null && params.length > 0) {
            IdentifyParameters mParams = params[0];

            try {
                // Run IdentifyTask with Identify Parameters

                M_Result = task.execute(mParams);

            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        return M_Result;
    }

    @Override
    protected void onPostExecute(IdentifyResult[] results) {

        // dismiss dialog
        if (dialog.isShowing()) {
            dialog.dismiss();
        }

        ArrayList<IdentifyResult> resultList = new ArrayList<IdentifyResult>();

        IdentifyResult result_1;

        for (int index = 0; index < results.length; index++) {

            result_1 = results[index];
            String displayFieldName = result_1.getDisplayFieldName();
            Map<String, Object> attr = result_1.getAttributes();
            for (String key : attr.keySet()) {
                if (key.equalsIgnoreCase(displayFieldName)) {
                    resultList.add(result_1);
                }
            }
        }

        Callout callout = mMapView.getCallout();
        callout.setContent(createIdentifyContent(resultList));
        callout.show(mAnchor);


    }
}
}

这是错误

06-11 19:01:21.384  18989-18989/com.tehranuni.hazard.hazard E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.tehranuni.hazard.hazard, PID: 18989
java.lang.NullPointerException: Attempt to get length of null array
        at com.tehranuni.hazard.hazard.gatter_geo_data$MyIdentifyTask.onPostExecute(gatter_geo_data.java:714)
        at com.tehranuni.hazard.hazard.gatter_geo_data$MyIdentifyTask.onPostExecute(gatter_geo_data.java:661)
        at android.os.AsyncTask.finish(AsyncTask.java:632)
        at android.os.AsyncTask.access$600(AsyncTask.java:177)
        at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:211)
        at android.app.ActivityThread.main(ActivityThread.java:5321)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1016)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:811)
        at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:117)

因为错误说 results 是空的，我认为这是因为它没有从 WMS 层获取字段。你怎么看待这个错误？有什么办法可以解决它吗？

非常感谢您的帮助

Answer 1

IdentifyTask仅适用于 ArcGIS Server map 服务，不适用于 WMS。