我正在开发一个Android项目，我想从当前位置绘制一条到特定商店的路线。以下是我的代码：
我调用异步类GetRouteTask调用另一个类。下面的代码如下所示：
public void placemarkersonmap()
{
googleMap.setMyLocationEnabled(true);
googleMap.getUiSettings().setMyLocationButtonEnabled(true);
googleMap.getUiSettings().setZoomControlsEnabled(true);
googleMap.getUiSettings().setCompassEnabled(true);
googleMap.getUiSettings().setAllGesturesEnabled(true);
googleMap.setTrafficEnabled(true);
new GetRouteTask().execute();
}
private class GetRouteTask extends AsyncTask<String, Void, String> {
private ProgressDialog Dialog;
String response = "";
@Override
protected void onPreExecute() {
Dialog = new ProgressDialog(getActivity());
Dialog.setMessage("Loading route...");
Dialog.setCancelable(false);
Dialog.show();
}
@Override
protected String doInBackground(String... urls) {
//Get All Route values
document = v2GetRouteDirection.getDocument(fromPosition, toPosition, GMapV2GetRouteDirection.MODE_DRIVING);
if(document!=null){
response = "Success";
}
return response;
}
@Override
protected void onPostExecute(String result) {
googleMap.clear();
if(response.equalsIgnoreCase("Success")){
ArrayList<LatLng> directionPoint = v2GetRouteDirection.getDirection(document);
PolylineOptions rectLine = new PolylineOptions().width(10).color(
Color.RED);
for (int i = 0; i < directionPoint.size(); i++) {
rectLine.add(directionPoint.get(i));
}
// Adding route on the map
googleMap.addPolyline(rectLine);
markerOptions.position(toPosition).title(job_object.job_shop_name);
markerOptions.draggable(true);
googleMap.addMarker(markerOptions);
googleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(fromPosition, 12f));
googleMap.animateCamera(CameraUpdateFactory.newLatLngZoom(fromPosition, 12f));
}
Dialog.dismiss();
}
}
助手类：
package com.igloo.classes;
import java.io.InputStream;
import java.util.ArrayList;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.protocol.BasicHttpContext;
import org.apache.http.protocol.HttpContext;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import com.google.android.gms.maps.model.LatLng;
import android.util.Log;
public class GMapV2GetRouteDirection {
public final static String MODE_DRIVING = "driving";
public final static String MODE_WALKING = "walking";
public GMapV2GetRouteDirection() { }
public Document getDocument(LatLng start, LatLng end, String mode) {
String url = "http://maps.googleapis.com/maps/api/directions/xml?"
+ "origin=" + start.latitude + "," + start.longitude
+ "&destination=" + end.latitude + "," + end.longitude
+ "&sensor=false&units=metric&mode=driving";
try {
HttpClient httpClient = new DefaultHttpClient();
HttpContext localContext = new BasicHttpContext();
HttpPost httpPost = new HttpPost(url);
HttpResponse response = httpClient.execute(httpPost, localContext);
InputStream in = response.getEntity().getContent();
DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
Document doc = builder.parse(in);
return doc;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
public String getDurationText (Document doc) {
NodeList nl1 = doc.getElementsByTagName("duration");
Node node1 = nl1.item(0);
NodeList nl2 = node1.getChildNodes();
Node node2 = nl2.item(getNodeIndex(nl2, "text"));
Log.i("DurationText", node2.getTextContent());
return node2.getTextContent();
}
public int getDurationValue (Document doc) {
NodeList nl1 = doc.getElementsByTagName("duration");
Node node1 = nl1.item(0);
NodeList nl2 = node1.getChildNodes();
Node node2 = nl2.item(getNodeIndex(nl2, "value"));
Log.i("DurationValue", node2.getTextContent());
return Integer.parseInt(node2.getTextContent());
}
public String getDistanceText (Document doc) {
NodeList nl1 = doc.getElementsByTagName("distance");
Node node1 = nl1.item(0);
NodeList nl2 = node1.getChildNodes();
Node node2 = nl2.item(getNodeIndex(nl2, "text"));
Log.i("DistanceText", node2.getTextContent());
return node2.getTextContent();
}
public int getDistanceValue (Document doc) {
NodeList nl1 = doc.getElementsByTagName("distance");
Node node1 = nl1.item(0);
NodeList nl2 = node1.getChildNodes();
Node node2 = nl2.item(getNodeIndex(nl2, "value"));
Log.i("DistanceValue", node2.getTextContent());
return Integer.parseInt(node2.getTextContent());
}
public String getStartAddress (Document doc) {
NodeList nl1 = doc.getElementsByTagName("start_address");
Node node1 = nl1.item(0);
Log.i("StartAddress", node1.getTextContent());
return node1.getTextContent();
}
public String getEndAddress (Document doc) {
NodeList nl1 = doc.getElementsByTagName("end_address");
Node node1 = nl1.item(0);
Log.i("StartAddress", node1.getTextContent());
return node1.getTextContent();
}
public String getCopyRights (Document doc) {
NodeList nl1 = doc.getElementsByTagName("copyrights");
Node node1 = nl1.item(0);
Log.i("CopyRights", node1.getTextContent());
return node1.getTextContent();
}
public ArrayList<LatLng> getDirection (Document doc) {
NodeList nl1, nl2, nl3;
ArrayList<LatLng> listGeopoints = new ArrayList<LatLng>();
nl1 = doc.getElementsByTagName("step");
if (nl1.getLength() > 0) {
for (int i = 0; i < nl1.getLength(); i++) {
Node node1 = nl1.item(i);
nl2 = node1.getChildNodes();
Node locationNode = nl2.item(getNodeIndex(nl2, "start_location"));
nl3 = locationNode.getChildNodes();
Node latNode = nl3.item(getNodeIndex(nl3, "lat"));
double lat = Double.parseDouble(latNode.getTextContent());
Node lngNode = nl3.item(getNodeIndex(nl3, "lng"));
double lng = Double.parseDouble(lngNode.getTextContent());
listGeopoints.add(new LatLng(lat, lng));
locationNode = nl2.item(getNodeIndex(nl2, "polyline"));
nl3 = locationNode.getChildNodes();
latNode = nl3.item(getNodeIndex(nl3, "points"));
ArrayList<LatLng> arr = decodePoly(latNode.getTextContent());
for(int j = 0 ; j < arr.size() ; j++) {
listGeopoints.add(new LatLng(arr.get(j).latitude, arr.get(j).longitude));
}
locationNode = nl2.item(getNodeIndex(nl2, "end_location"));
nl3 = locationNode.getChildNodes();
latNode = nl3.item(getNodeIndex(nl3, "lat"));
lat = Double.parseDouble(latNode.getTextContent());
lngNode = nl3.item(getNodeIndex(nl3, "lng"));
lng = Double.parseDouble(lngNode.getTextContent());
listGeopoints.add(new LatLng(lat, lng));
}
}
return listGeopoints;
}
private int getNodeIndex(NodeList nl, String nodename) {
for(int i = 0 ; i < nl.getLength() ; i++) {
if(nl.item(i).getNodeName().equals(nodename))
return i;
}
return -1;
}
private ArrayList<LatLng> decodePoly(String encoded) {
ArrayList<LatLng> poly = new ArrayList<LatLng>();
int index = 0, len = encoded.length();
int lat = 0, lng = 0;
while (index < len) {
int b, shift = 0, result = 0;
do {
b = encoded.charAt(index++) - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
int dlat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
lat += dlat;
shift = 0;
result = 0;
do {
b = encoded.charAt(index++) - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
int dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
lng += dlng;
LatLng position = new LatLng((double) lat / 1E5, (double) lng / 1E5);
poly.add(position);
}
return poly;
}
}
我在较新的设备上工作正常。但在较旧的设备（Android 2.6）上，我遇到以下异常：
11-08 11:14:24.709: W/System.err(4582): java.net.UnknownHostException: maps.googleapis.com
11-08 11:14:24.740: W/System.err(4582): at java.net.InetAddress.lookupHostByName(InetAddress.java:506)
11-08 11:14:24.740: W/System.err(4582): at java.net.InetAddress.getAllByNameImpl(InetAddress.java:294)
11-08 11:14:24.748: W/System.err(4582): at java.net.InetAddress.getAllByName(InetAddress.java:256)
11-08 11:14:24.748: W/System.err(4582): at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:136)
11-08 11:14:24.748: W/System.err(4582): at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
11-08 11:14:24.748: W/System.err(4582): at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
11-08 11:14:24.748: W/System.err(4582): at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:359)
11-08 11:14:24.748: W/System.err(4582): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
11-08 11:14:24.748: W/System.err(4582): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
11-08 11:14:24.748: W/System.err(4582): at com.igloo.classes.GMapV2GetRouteDirection.getDocument(GMapV2GetRouteDirection.java:37)
11-08 11:14:24.748: W/System.err(4582): at com.igloo.fragments.RouteFragment$GetRouteTask.doInBackground(RouteFragment.java:282)
11-08 11:14:24.748: W/System.err(4582): at com.igloo.fragments.RouteFragment$GetRouteTask.doInBackground(RouteFragment.java:1)
11-08 11:14:24.748: W/System.err(4582): at android.os.AsyncTask$2.call(AsyncTask.java:185)
11-08 11:14:24.748: W/System.err(4582): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306)
11-08 11:14:24.748: W/System.err(4582): at java.util.concurrent.FutureTask.run(FutureTask.java:138)
11-08 11:14:24.748: W/System.err(4582): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088)
11-08 11:14:24.748: W/System.err(4582): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581)
11-08 11:14:24.748: W/System.err(4582): at java.lang.Thread.run(Thread.java:1019)
11-08 11:15:33.982: W/System.err(4582): java.net.UnknownHostException: maps.googleapis.com
11-08 11:15:33.990: W/System.err(4582): at java.net.InetAddress.lookupHostByName(InetAddress.java:506)
11-08 11:15:33.990: W/System.err(4582): at java.net.InetAddress.getAllByNameImpl(InetAddress.java:294)
11-08 11:15:33.998: W/System.err(4582): at java.net.InetAddress.getAllByName(InetAddress.java:256)
11-08 11:15:33.998: W/System.err(4582): at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:136)
11-08 11:15:33.998: W/System.err(4582): at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
11-08 11:15:33.998: W/System.err(4582): at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
11-08 11:15:33.998: W/System.err(4582): at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:359)
11-08 11:15:33.998: W/System.err(4582): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
11-08 11:15:33.998: W/System.err(4582): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
11-08 11:15:33.998: W/System.err(4582): at com.igloo.classes.GMapV2GetRouteDirection.getDocument(GMapV2GetRouteDirection.java:37)
11-08 11:15:33.998: W/System.err(4582): at com.igloo.fragments.RouteFragment$GetRouteTask.doInBackground(RouteFragment.java:282)
11-08 11:15:33.998: W/System.err(4582): at com.igloo.fragments.RouteFragment$GetRouteTask.doInBackground(RouteFragment.java:1)
11-08 11:15:33.998: W/System.err(4582): at android.os.AsyncTask$2.call(AsyncTask.java:185)
11-08 11:15:34.006: W/System.err(4582): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306)
11-08 11:15:34.006: W/System.err(4582): at java.util.concurrent.FutureTask.run(FutureTask.java:138)
11-08 11:15:34.006: W/System.err(4582): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088)
11-08 11:15:34.006: W/System.err(4582): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581)
11-08 11:15:34.006: W/System.err(4582): at java.lang.Thread.run(Thread.java:1019)
11-08 11:15:47.576: W/KeyCharacterMap(4582): No keyboard for id 0
11-08 11:15:47.576: W/KeyCharacterMap(4582): Using default keymap
显示的错误行是这一行：
HttpResponse response = httpClient.execute(httpPost, localContext);
在辅助类中。
问题是为什么这段代码在某些时候起作用而在其他时候不起作用？ 我该如何解决这个问题？