Android GIS開發系列-- 入門季（5） FeatureLayer載入本地shp檔案與要素查詢

 

FeatureLayer是要素圖層，也是Arcgis的主要圖層。用這個圖層可以載入本地的shp檔案。下面我們看怎樣載入shp檔案到MapView中。檢視ArcGis API可知FeatureLayer的構造方法要傳一個FeatureTable，而FeatureTable可用子類ShapefileFeatureTable來實現。程式碼如下，其中shpPath為shp檔案的本地路徑。\

 

private void initLayer() {
        try {

            featureLayer = new FeatureLayer(new ShapefileFeatureTable(
                    shpPath));
            featureLayer.setRenderer(new SimpleRenderer(new SimpleFillSymbol(
                    Color.GREEN)));

            mapView.addLayer(featureLayer);

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

效果圖如下。

這樣就可以很簡單地載入shp檔案了。下面我們來學習一下FeatureLayer的查詢。

一、FeatureLayer點選查詢主要用到的方法是featureLayer.getFeatureIDs(float x, float y, int tolerance)，方法與上一講GraphicsLayer的查詢差不多。可以獲取每個要素的屬性屬性值。

 

private void handleSingleTap(float x, float y) {

        long[] featureIds = featureLayer.getFeatureIDs(x, y, 8);
        if (featureIds != null && featureIds.length > 0) {
            for (long id : featureIds) {
                com.esri.core.map.Feature feature = featureLayer.getFeature(id);
                Map<String, Object> attrs = feature.getAttributes();
                Set<Entry<String, Object>> setEntry = attrs.entrySet();
                for (Entry<String, Object> entryItem : setEntry) {
                    Log.e(TAG,
                            entryItem.getKey() + "====" + entryItem.getValue());
                }
            }

        }
    }

二、利用FeatureTable查詢，這是FeatureLayer特別的地方。比如在一個shp檔案中，有多個要素，我們知道有每個要素中有name這個屬性，怎樣快速查詢name為shanghai的要素呢？要用到FeatureTable的queryFeatures(QueryParameters query, CallbackListener<FeatureResult> callback)方法或者是queryIds(QueryParameters query, CallbackListener<long[]> callback)這個方法。

 

private void queryTable() {
        FeatureTable featureTable = featureLayer.getFeatureTable();
        QueryParameters parameters = new QueryParameters();
        //查詢條件，有點像資料庫中的查詢
        parameters.setWhere("name = 'shanghai'");<span style="white-space:pre">                     </span>Future<long[]> queryIds = featureTable.queryIds(parameters,new CallbackListener<long[]>() {

                    @Override
                    public void onError(Throwable arg0) {
                        // TODO Auto-generated method stub

                    }

                    @Override
                    public void onCallback(long[] arg0) {
                        // TODO Auto-generated method stub

                    }
                });

        try {
            long[] Ids = queryIds.get();
            if (Ids != null && Ids.length > 0) {
                for (int i = 0; i < Ids.length; i++) {
                    Feature feature = featureLayer.getFeature(Ids[i]);
                    Log.i(TAG, feature.getAttributes().get("name") + "");
                }
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }

 

這樣就可以快速查詢到某個具體的要素。

package com.huang.featuer;

import java.util.Map;

import java.util.Map.Entry;

import java.util.Set;

import java.util.concurrent.ExecutionException;

import java.util.concurrent.Future;

import android.app.Activity;

import android.graphics.Color;

import android.os.Bundle;

import android.os.Environment;

import android.util.Log;

import android.view.View;

import android.view.View.OnClickListener;

import com.esri.android.map.FeatureLayer;

import com.esri.android.map.MapView;

import com.esri.android.map.event.OnSingleTapListener;

import com.esri.core.geodatabase.ShapefileFeatureTable;

import com.esri.core.map.CallbackListener;

import com.esri.core.map.Feature;

import com.esri.core.renderer.SimpleRenderer;

import com.esri.core.symbol.SimpleFillSymbol;

import com.esri.core.table.FeatureTable;

import com.esri.core.tasks.query.QueryParameters;

public class FeatureLayerActivity extends Activity implements OnClickListener {

private static final String TAG = FeatureLayerActivity.class.getName();

private MapView mMapView;

private String shpPath = Environment.getExternalStorageDirectory()

.getAbsolutePath() + "/test/test.shp";

private FeatureLayer featureLayer;

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);



mMapView = (MapView) findViewById(R.id.mapView);

findViewById(R.id.query_btn).setOnClickListener(this);

initLayer();



mMapView.setOnSingleTapListener(new OnSingleTapListener() {

public void onSingleTap(float x, float y) {

handleSingleTap(x, y);

}

});

}



private void initLayer() {

try {

featureLayer = new FeatureLayer(new ShapefileFeatureTable(shpPath));

featureLayer.setRenderer(new SimpleRenderer(new SimpleFillSymbol(

Color.GREEN)));

mMapView.addLayer(featureLayer);

} catch (Exception e) {

e.printStackTrace();

}

}

private void handleSingleTap(float x, float y) {

long[] featureIds = featureLayer.getFeatureIDs(x, y, 8);

if (featureIds != null && featureIds.length > 0) {

for (long id : featureIds) {

com.esri.core.map.Feature feature = featureLayer.getFeature(id);

Map<String, Object> attrs = feature.getAttributes();

Set<Entry<String, Object>> setEntry = attrs.entrySet();

for (Entry<String, Object> entryItem : setEntry) {

Log.e(TAG,

entryItem.getKey() + "====" + entryItem.getValue());

}

}

}

}



public void onClick(View v) {

switch (v.getId()) {

case R.id.query_btn:

query();

break;

default:

break;

}

}



private void query() {

FeatureTable featureTable = featureLayer.getFeatureTable();

QueryParameters parameters = new QueryParameters();

// 查詢條件，有點像資料庫中的查詢

parameters.setWhere("name = 'shanghai'");

Future<long[]> queryIds = featureTable.queryIds(parameters,

new CallbackListener<long[]>() {

public void onError(Throwable e) {

// TODO Auto-generated method stub

}

public void onCallback(long[] objs) {

// TODO Auto-generated method stub

}

});

try {

long[] Ids = queryIds.get();

if (Ids != null && Ids.length > 0) {

for (int i = 0; i < Ids.length; i++) {

Feature feature = featureLayer.getFeature(Ids[i]);

Log.i(TAG, feature.getAttributes().get("name") + "");

}

}

} catch (InterruptedException e) {

e.printStackTrace();

} catch (ExecutionException e) {

e.printStackTrace();

}

}

}