如何将对象从asynctask返回到android中的主类
我想将文档返回到我的主类，但即使使用全局变量也不会工作，因为asynctask没有完成工作我认为有一个解决方案来获取对象formsasynctask吗？ 我已经在onPostExecute中尝试了做法，但是如果我在asynctask之外，那么对象就是null，这是类：
private class RequestTask extends AsyncTask { protected Document doInBackground(String... url) { try { HttpClient httpClient = new DefaultHttpClient(); HttpContext localContext = new BasicHttpContext(); HttpPost httpPost = new HttpPost(url[0]); HttpResponse response = httpClient.execute(httpPost, localContext); InputStream in = response.getEntity().getContent(); DocumentBuilder builder = DocumentBuilderFactory.newInstance() .newDocumentBuilder(); return builder.parse(in); } catch (IOException e) { e.printStackTrace(); } catch (ParserConfigurationException e) { e.printStackTrace(); } catch (SAXException e) { e.printStackTrace(); } return null; } protected void onPostExecute(Document doc) { super.onPostExecute(doc); if (mDirectionListener != null) { mDirectionListener.onResponse(getStatus(doc), doc, GoogleDirection.this); } } private String getStatus(Document doc) { NodeList nl1 = doc.getElementsByTagName("status"); Node node1 = nl1.item(0); if (isLogging) { Log.i("GoogleDirection", "Status : " + node1.getTextContent()); } return node1.getTextContent(); } } 我尝试了很多解决方案，其中没有一个工作……请帮助我！
更新：我得到的一些错误： 
我的代码结构：ClassMain，Class GoogleDirection和innerClass是asynctask
这是我的第一个包含内部类（Asynctask）包com.example.busmapsproject.app的类;
import android.annotation.SuppressLint; import android.content.Context; import android.os.AsyncTask; import android.util.DisplayMetrics; import android.util.Log; import com.google.android.gms.maps.model.LatLng; import com.google.android.gms.maps.model.PolylineOptions; 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 org.xml.sax.SAXException; import java.io.IOException; import java.io.InputStream; import java.util.ArrayList; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.parsers.ParserConfigurationException; @SuppressLint("NewApi") public class GoogleDirection { public final static String MODE_WALKING = "walking"; private OnDirectionResponseListener mDirectionListener = null; private boolean isLogging = false; private Context myContext = null; private Document test; public GoogleDirection(Context context) { myContext = context; } public String request(LatLng start, LatLng end, String mode) { final 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=" + mode; if (isLogging) { //Display information in logcat (report success) Log.i("GoogleDirection", "URL : " + url); } new RequestTask().execute(url); return url; } public void setLogging(boolean state) { isLogging = state; } public String getStatus(Document doc) { NodeList nl1 = doc.getElementsByTagName("status"); Node node1 = nl1.item(0); if (isLogging) { Log.i("GoogleDirection", "Status : " + node1.getTextContent()); } return node1.getTextContent(); } public String[] getDurationText(Document doc) { NodeList nl1 = doc.getElementsByTagName("duration"); String[] arr_str = new String[nl1.getLength() - 1]; for (int i = 0; i < (nl1.getLength() - 1); i++) { Node node1 = nl1.item(i); NodeList nl2 = node1.getChildNodes(); //Return child of a node (Duration have text and value) Node node2 = nl2.item(getNodeIndex(nl2, "text")); arr_str[i] = node2.getTextContent(); if (isLogging) { Log.i("GoogleDirection", "DurationText : " + node2.getTextContent()); } } return arr_str; } public int[] getDurationValue(Document doc) { NodeList nl1 = doc.getElementsByTagName("duration"); int[] arr_int = new int[nl1.getLength() - 1]; for (int i = 0; i < (nl1.getLength() - 1); i++) { Node node1 = nl1.item(i); NodeList nl2 = node1.getChildNodes(); Node node2 = nl2.item(getNodeIndex(nl2, "value")); arr_int[i] = Integer.parseInt(node2.getTextContent()); if (isLogging) { Log.i("GoogleDirection", "Duration : " + node2.getTextContent()); } } return arr_int; } public String getTotalDurationText(Document doc) { NodeList nl1 = doc.getElementsByTagName("duration"); Node node1 = nl1.item(nl1.getLength() - 1); NodeList nl2 = node1.getChildNodes(); Node node2 = nl2.item(getNodeIndex(nl2, "text")); if (isLogging) { Log.i("GoogleDirection", "TotalDuration : " + node2.getTextContent()); } return node2.getTextContent(); } public int getTotalDurationValue(Document doc) { NodeList nl1 = doc.getElementsByTagName("duration"); Node node1 = nl1.item(nl1.getLength() - 1); NodeList nl2 = node1.getChildNodes(); Node node2 = nl2.item(getNodeIndex(nl2, "value")); if (isLogging) { Log.i("GoogleDirection", "TotalDuration : " + node2.getTextContent()); } return Integer.parseInt(node2.getTextContent()); } public String[] getDistanceText(Document doc) { NodeList nl1 = doc.getElementsByTagName("distance"); String[] arr_str = new String[nl1.getLength() - 1]; for (int i = 0; i < (nl1.getLength() - 1); i++) { Node node1 = nl1.item(i); NodeList nl2 = node1.getChildNodes(); Node node2 = nl2.item(getNodeIndex(nl2, "text")); arr_str[i] = node2.getTextContent(); if (isLogging) { Log.i("GoogleDirection", "DurationText : " + node2.getTextContent()); } } return arr_str; } public int[] getDistanceValue(Document doc) { NodeList nl1 = doc.getElementsByTagName("distance"); int[] arr_int = new int[nl1.getLength() - 1]; for (int i = 0; i < (nl1.getLength() - 1); i++) { Node node1 = nl1.item(i); NodeList nl2 = node1.getChildNodes(); Node node2 = nl2.item(getNodeIndex(nl2, "value")); arr_int[i] = Integer.parseInt(node2.getTextContent()); if (isLogging) { Log.i("GoogleDirection", "Duration : " + node2.getTextContent()); } } return arr_int; } public String getTotalDistanceText(Document doc) { NodeList nl1 = doc.getElementsByTagName("distance"); Node node1 = nl1.item(nl1.getLength() - 1); NodeList nl2 = node1.getChildNodes(); Node node2 = nl2.item(getNodeIndex(nl2, "text")); if (isLogging) { Log.i("GoogleDirection", "TotalDuration : " + node2.getTextContent()); } return node2.getTextContent(); } public int getTotalDistanceValue(Document doc) { NodeList nl1 = doc.getElementsByTagName("distance"); Node node1 = nl1.item(nl1.getLength() - 1); NodeList nl2 = node1.getChildNodes(); Node node2 = nl2.item(getNodeIndex(nl2, "value")); if (isLogging) { Log.i("GoogleDirection", "TotalDuration : " + node2.getTextContent()); } return Integer.parseInt(node2.getTextContent()); } public String getStartAddress(Document doc) { NodeList nl1 = doc.getElementsByTagName("start_address"); Node node1 = nl1.item(0); if (isLogging) { Log.i("GoogleDirection", "StartAddress : " + node1.getTextContent()); } return node1.getTextContent(); } public String getEndAddress(Document doc) { NodeList nl1 = doc.getElementsByTagName("end_address"); Node node1 = nl1.item(0); if (isLogging) { Log.i("GoogleDirection", "StartAddress : " + node1.getTextContent()); } return node1.getTextContent(); } public String getCopyRights(Document doc) { NodeList nl1 = doc.getElementsByTagName("copyrights"); Node node1 = nl1.item(0); if (isLogging) { Log.i("GoogleDirection", "CopyRights : " + node1.getTextContent()); } return node1.getTextContent(); } public ArrayList getDirection(Document doc) { NodeList nl1; NodeList nl2; NodeList nl3; ArrayList listGeopoints = new ArrayList(); 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 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; } public ArrayList getSection(Document doc) { NodeList nl1; NodeList nl2; NodeList nl3; ArrayList listGeopoints = new ArrayList(); 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, "end_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)); } } return listGeopoints; } public PolylineOptions getPolyline(Document doc, int width, int color) { ArrayList arr_pos = getDirection(doc); PolylineOptions rectLine = new PolylineOptions().width(dpToPx(width)) .color(color); for (int i = 0; i < arr_pos.size(); i++) rectLine.add(arr_pos.get(i)); return rectLine; } 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 decodePoly(String encoded) { ArrayList poly = new ArrayList(); int index = 0; int len = encoded.length(); int lat = 0; int lng = 0; while (index < len) { int b; int shift = 0; int result = 0; do { b = encoded.charAt(index++) - 63; result |= ((b & 0x1f) <= 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) <= 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; } //Convert dp to pixel private int dpToPx(int dp) { DisplayMetrics displayMetrics = myContext.getResources() .getDisplayMetrics(); int px = Math.round(dp * (displayMetrics.xdpi / DisplayMetrics.DENSITY_DEFAULT)); return px; } public void setOnDirectionResponseListener( OnDirectionResponseListener listener) { mDirectionListener = listener; } public interface OnDirectionResponseListener { public void onResponse(String status, Document doc, GoogleDirection gd); } private class RequestTask extends AsyncTask { protected Document doInBackground(String... url) { try { HttpClient httpClient = new DefaultHttpClient(); HttpContext localContext = new BasicHttpContext(); HttpPost httpPost = new HttpPost(url[0]); HttpResponse response = httpClient.execute(httpPost, localContext); InputStream in = response.getEntity().getContent(); DocumentBuilder builder = DocumentBuilderFactory.newInstance() .newDocumentBuilder(); return builder.parse(in); } catch (IOException e) { e.printStackTrace(); } catch (ParserConfigurationException e) { e.printStackTrace(); } catch (SAXException e) { e.printStackTrace(); } return null; } protected void onPostExecute(Document doc) { super.onPostExecute(doc); if (mDirectionListener != null) { mDirectionListener.onResponse(getStatus(doc), doc, GoogleDirection.this); } } private String getStatus(Document doc) { NodeList nl1 = doc.getElementsByTagName("status"); Node node1 = nl1.item(0); if (isLogging) { Log.i("GoogleDirection", "Status : " + node1.getTextContent()); } return node1.getTextContent(); } } }
这是我的主要类：import android.graphics.Color; import android.os.Bundle; import android.support.v4.app.FragmentActivity;
import com.google.android.gms.maps.GoogleMap; import com.google.android.gms.maps.SupportMapFragment; import com.google.android.gms.maps.model.BitmapDescriptorFactory; import com.google.android.gms.maps.model.LatLng; import com.google.android.gms.maps.model.MarkerOptions; import org.w3c.dom.Document; public class MapsActivity extends FragmentActivity { private GoogleMap mMap; // Might be null if Google Play services APK is not available. private GoogleDirection gd; private LatLng Arret=new LatLng(30.413647, -9.555608); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_maps); gd = new GoogleDirection(this); setUpMapIfNeeded(); } @Override protected void onResume() { super.onResume(); setUpMapIfNeeded(); } /** * Sets up the map if it is possible to do so (ie, the Google Play services APK is correctly * installed) and the map has not already been instantiated.. This will ensure that we only ever * call {@link #setUpMap()} once when {@link #mMap} is not null. * * If it isn't installed {@link SupportMapFragment} (and * {@link com.google.android.gms.maps.MapView MapView}) will show a prompt for the user to * install/update the Google Play services APK on their device. *
* A user can return to this FragmentActivity after following the prompt and correctly * installing/updating/enabling the Google Play services. Since the FragmentActivity may not * have been completely destroyed during this process (it is likely that it would only be * stopped or paused), {@link #onCreate(Bundle)} may not be called again so we should call this * method in {@link #onResume()} to guarantee that it will be called. */ private void setUpMapIfNeeded() { // Do a null check to confirm that we have not already instantiated the map. if (mMap == null) { // Try to obtain the map from the SupportMapFragment. mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map)) .getMap(); mMap.setMyLocationEnabled(true); // Check if we were successful in obtaining the map. if (mMap != null) { setUpMap(); } } } /** * This is where we can add markers or lines, add listeners or move the camera. In this case, we * just add a marker near Africa. *
* This should only be called once and when we are sure that {@link #mMap} is not null. */ private void setUpMap() { MyLocation loc=new MyLocation(this); mMap.addMarker(new MarkerOptions().position(new LatLng(loc.getLatitude(),loc.getLongitude())) .icon(BitmapDescriptorFactory.defaultMarker( BitmapDescriptorFactory.HUE_BLUE))); mMap.addMarker(new MarkerOptions().position(Arret) .icon(BitmapDescriptorFactory.defaultMarker( BitmapDescriptorFactory.HUE_BLUE))); gd.setOnDirectionResponseListener(new GoogleDirection.OnDirectionResponseListener() { @Override public void onResponse(String status, Document doc, GoogleDirection gd) { mMap.addPolyline(gd.getPolyline(doc, 3, Color.RED)); gd.getTotalDurationValue(doc); } }); gd.setLogging(true); //LatLng test=new LatLng((loc.getLatitude()+0.1f),(loc.getLongitude()+0.5f)); gd.request(new LatLng(loc.getLatitude(),loc.getLongitude()), Arret , GoogleDirection.MODE_WALKING); } }
使用监听器监听器。 2分钟的例子。
使用如下界面：
public interface OnTaskCompleted{ void onTaskCompleted(Document doc); }
使用此界面扩展您的活动：
public YourActivity implements OnTaskCompleted{ //your Activity }
让AsyncTask在完成后发送信息。
public YourTask extends AsyncTask{ private OnTaskCompleted listener; // all your stuff public YourTask(OnTaskCompleted listener){ this.listener=listener; } protected void onPostExecute(Object o){ listener.onTaskCompleted(doc); } }
现在，您在活动中实现onTaskCompleted并处理asynctask提供的Document。
OnPostExecute是您在主线程中完成下载后接收文档的位置，也就是您要返回旅游项目的位置。
我发现你可以在asynctask中实现一个构造函数，比如
private class RequestTask extends AsyncTask { private MainClass myClass public RequestTask(MainClass myClass){ this.myClass = myClass } ... protected void onPostExecute(Document doc) { super.onPostExecute(doc); myClass.myMethod(doc); } ... }
这样您就可以在主类中接收文档
希望能帮助到你
问候
你可以调用另一个函数，例如：
protected void onPostExecute(Document doc) { documentIsReady(doc); } } public void documentIsReady(Document doc) { //Do somehting }