我有一个看起来很容易找到的东西，但是我正在查看所有变量，找不到空值。我最近将MyGeocoderTask类从LocationMain中分离出来，这可能是我弄糟的地方。以前效果很好。 :(现在，当我单击激活findThroughPopup()的按钮时，应用程序崩溃。我仍然不是完全愿意在需要时将变量转移到其他类的专业人员，因此，除了查找哪个为null之外，我可能还应该也可以帮助正确编码，下面是我的两个类和stacktrace。感谢您的帮助。
LocationMain.java
package org.azurespot.practiceapp.location;
import org.azurespot.practiceapp.R;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.FragmentManager;
import android.content.Context;
import android.content.DialogInterface;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationManager;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.EditText;
import android.widget.FrameLayout;
import com.google.android.gms.maps.CameraUpdate;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
public class LocationMain extends Activity {
public static FragmentManager fragmentManager;
public final int RQS_GooglePlayServices = 1;
protected static Double latitude;
protected static Double longitude;
protected static Context context;
protected static EditText addressInput;
protected LatLng myPosition;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_location_main);
fragmentManager = getFragmentManager();
}
// locates the user's location
public void findMe(View v){
if (LocationFragment.mMap == null){
LocationFragment.setUpMapIfNeeded();
}
if (LocationFragment.mMap != null) {
// Enabling MyLocation Layer of Google Map
LocationFragment.mMap.setMyLocationEnabled(true);
// Getting LocationManager object from System Service LOCATION_SERVICE
LocationManager locationManager = (LocationManager)
getSystemService(LOCATION_SERVICE);
// Creating a criteria object to retrieve provider
Criteria criteria = new Criteria();
// Getting the name of the best provider
String provider = locationManager.getBestProvider(criteria, true);
// Getting Current Location
Location location = locationManager.getLastKnownLocation(provider);
latitude = location.getLatitude();
longitude = location.getLongitude();
// Creating a LatLng object for the current location
myPosition = new LatLng(latitude, longitude);
LocationFragment.mMap.addMarker(new MarkerOptions().position
(myPosition).title("Start"));
// For zooming automatically to the Dropped PIN Location
LocationFragment.mMap.animateCamera(CameraUpdateFactory.newLatLngZoom
(new LatLng(latitude, longitude), 12.0f));
}
}
// enter address of your choosing into the Dialog box
public void findThroughPopup(View v) {
AlertDialog.Builder builder = new AlertDialog.Builder(this);
// set title
builder.setTitle("Enter an address");
// set EditText into your dialog box layout, using FrameLayout
final FrameLayout frameView = new FrameLayout(this);
builder.setView(frameView);
// must inflate EditText separately
AlertDialog alertDialog = builder.create();
LayoutInflater inflater = alertDialog.getLayoutInflater();
View etView = inflater.inflate(R.layout.alert_dialog_edit_text, frameView);
// initialize EditText, use etView to pull from its specific XML
addressInput = (EditText)etView.findViewById(R.id.address_field);
// set Find button that finds address by showing on map
builder.setPositiveButton("Find", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int id) {
// go through map setup if needed, otherwise process address input
if (LocationFragment.mMap == null){
LocationFragment.setUpMapIfNeeded();
}
if (LocationFragment.mMap != null) {
String userLocale = addressInput.getText().toString();
if(userLocale!=null && !userLocale.equals("")){
new MyGeocoderTask().execute(userLocale);
}
}
// zooms in to wherever you map ends up,
// the 15f is in a range of 2.0 - 21.0
CameraUpdate camZoom = CameraUpdateFactory.zoomTo(12f);
LocationFragment.mMap.animateCamera(camZoom);
}
});
// set Cancel button
builder.setNegativeButton("Cancel",new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int id) {
// if this button is clicked, just close
// the dialog box and do nothing
dialog.cancel();
}
});
// put all your builders in one create command
alertDialog = builder.create();
// show the dialog box
alertDialog.show();
} // end findThroughPopup()
// resets map when back button is pressed
@Override
public void onBackPressed()
{
super.onBackPressed();
LocationFragment.onBackPressed();
}
}
MyGeocoderTask.java
package org.azurespot.practiceapp.location;
import java.io.IOException;
import java.util.List;
import android.location.Address;
import android.location.Geocoder;
import android.os.AsyncTask;
import android.widget.Toast;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
/***An AsyncTask class for accessing the GeoCoding Web Service****/
public class MyGeocoderTask extends AsyncTask<String, Void, List<Address>>{
protected LatLng enteredAddress;
protected MarkerOptions markerOptions;
@Override
protected List<Address> doInBackground(String... locationName) {
// Creating an instance of Geocoder class
Geocoder geocoder = new Geocoder(LocationMain.context);
List<Address> addresses = null;
try {
// Getting a maximum of 3 Address that matches the input text
addresses = geocoder.getFromLocationName(locationName[0], 3);
} catch (IOException e) {
e.printStackTrace();
}
return addresses;
}
// part of the GeocoderTask life cycle
@Override
protected void onPostExecute(List<Address> addresses) {
if(addresses==null || addresses.size()==0){
Toast.makeText(LocationMain.context, "No Location found",
Toast.LENGTH_SHORT).show();
}
// Clears all the existing markers on the map
LocationFragment.mMap.clear();
// Adding Markers on Google Map for each matching address
for(int i=0;i<addresses.size();i++){
Address address = (Address) addresses.get(i);
// Creating an instance of GeoPoint, to display in Google Map
enteredAddress = new LatLng(address.getLatitude(), address.getLongitude());
String addressText = String.format("%s, %s",
address.getMaxAddressLineIndex() > 0 ? address.getAddressLine(0) : "",
address.getCountryName());
markerOptions = new MarkerOptions();
markerOptions.position(enteredAddress);
markerOptions.title(addressText);
LocationFragment.mMap.addMarker(markerOptions);
// Locate the first location
if(i==0)
LocationFragment.mMap.animateCamera
(CameraUpdateFactory.newLatLng(enteredAddress));
}
}
}
Logcat
12-29 22:55:00.444: D/AbsListView(20174): unregisterIRListener() is called
12-29 22:55:06.154: W/dalvikvm(20174): threadid=24: thread exiting with uncaught exception (group=0x41737da0)
12-29 22:55:06.154: E/AndroidRuntime(20174): FATAL EXCEPTION: AsyncTask #1
12-29 22:55:06.154: E/AndroidRuntime(20174): Process: org.azurespot.practiceapp, PID: 20174
12-29 22:55:06.154: E/AndroidRuntime(20174): java.lang.RuntimeException: An error occured while executing doInBackground()
12-29 22:55:06.154: E/AndroidRuntime(20174): at android.os.AsyncTask$3.done(AsyncTask.java:300)
12-29 22:55:06.154: E/AndroidRuntime(20174): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
12-29 22:55:06.154: E/AndroidRuntime(20174): at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
12-29 22:55:06.154: E/AndroidRuntime(20174): at java.util.concurrent.FutureTask.run(FutureTask.java:242)
12-29 22:55:06.154: E/AndroidRuntime(20174): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
12-29 22:55:06.154: E/AndroidRuntime(20174): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
12-29 22:55:06.154: E/AndroidRuntime(20174): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
12-29 22:55:06.154: E/AndroidRuntime(20174): at java.lang.Thread.run(Thread.java:841)
12-29 22:55:06.154: E/AndroidRuntime(20174): Caused by: java.lang.NullPointerException
12-29 22:55:06.154: E/AndroidRuntime(20174): at android.location.GeocoderParams.<init>(GeocoderParams.java:50)
12-29 22:55:06.154: E/AndroidRuntime(20174): at android.location.Geocoder.<init>(Geocoder.java:83)
12-29 22:55:06.154: E/AndroidRuntime(20174): at android.location.Geocoder.<init>(Geocoder.java:95)
12-29 22:55:06.154: E/AndroidRuntime(20174): at org.azurespot.practiceapp.location.MyGeocoderTask.doInBackground(MyGeocoderTask.java:26)
12-29 22:55:06.154: E/AndroidRuntime(20174): at org.azurespot.practiceapp.location.MyGeocoderTask.doInBackground(MyGeocoderTask.java:1)
12-29 22:55:06.154: E/AndroidRuntime(20174): at android.os.AsyncTask$2.call(AsyncTask.java:288)
12-29 22:55:06.154: E/AndroidRuntime(20174): at java.util.concurrent.FutureTask.run(FutureTask.java:237)
12-29 22:55:06.154: E/AndroidRuntime(20174): ... 4 more
12-29 22:55:06.164: D/AbsListView(20174): unregisterIRListener() is called
12-29 22:55:06.164: E/ViewRootImpl(20174): sendUserActionEvent() mView == null
12-29 22:55:06.374: D/AbsListView(20174): unregisterIRListener() is called
12-29 22:55:06.784: D/AbsListView(20174): onDetachedFromWindow
12-29 22:55:06.784: D/AbsListView(20174): unregisterIRListener() is called
12-29 22:55:07.524: I/Process(20174): Sending signal. PID: 20174 SIG: 9
最佳答案
根据您的代码，可能是LocationMain.context=null中的MyGeocoderTask。
因此，您可能像这样在Constructor中将上下文作为MyGeocoderTask传递
private Context mainContxt;
public MyGeocoderTask(Context con){
mainContxt=com;
}
并像
Geocoder geocoder = new Geocoder(mainContxt);
并从
Activity调用，例如 new MyGeocoderTask(your_Activity.this).execute(userLocale);
更新：
new MyGeocoderTask(getApplicationContext()).execute(userLocale);