问题
I am using Geocoding to retrieve addresses of latitude,longitude values. I'm implementing this GeoCoding in a seperate class extending IntentService. When I retrieve the address I want to send it back to the original main activity, and for this i use ResultReciever, and actually following the tutorial.
This is the class that I use to GeoCode i.e. transfer GPS coordinates to physical addresses. I get error when invoking the function call deliverResultToReceiver in onHandleIntent
public class FetchAddressIntentService extends IntentService {
protected ResultReceiver mReceiver;
public FetchAddressIntentService() {
super("GPSGame");
}
@Override
protected void onHandleIntent(Intent intent) {
Geocoder geocoder = new Geocoder(this, Locale.getDefault());
String errorMessage = "";
// Get the location passed to this service through an extra.
Location location = intent.getParcelableExtra(
Constants.LOCATION_DATA_EXTRA);
Log.e("LAT",Double.toString(location.getLatitude()));
Log.e("LONG",Double.toString(location.getLongitude()));
List<Address> addresses = null; /*** ADDRESS CAN BE OF ANOTHER LIBRARY ***/
try {
addresses = geocoder.getFromLocation(
location.getLatitude(),
location.getLongitude(),
// In this sample, get just a single address.
1);
} catch (IOException ioException) {
// Catch network or other I/O problems.
errorMessage = "service not available";
Log.e("exception", errorMessage);
} catch (IllegalArgumentException illegalArgumentException) {
// Catch invalid latitude or longitude values.
errorMessage = "IllegalArgumentException";
Log.e("Exception", errorMessage + ". " +
"Latitude = " + location.getLatitude() +
", Longitude = " +
location.getLongitude(), illegalArgumentException);
}
// Handle case where no address was found.
if (addresses == null || addresses.size() == 0) {
if (errorMessage == "") {
errorMessage = "no address found";
Log.e("address", errorMessage);
}
deliverResultToReceiver(Constants.FAILURE_RESULT, errorMessage);
}
else {
Address address = addresses.get(0);
ArrayList<String> addressFragments = new ArrayList<String>();
// Fetch the address lines using getAddressLine,
// join them, and send them to the thread.
for(int i = 0; i < address.getMaxAddressLineIndex(); i++) {
addressFragments.add(address.getAddressLine(i));
}
Log.i("address", "address found");
deliverResultToReceiver(Constants.SUCCESS_RESULT,
TextUtils.join(System.getProperty("line.separator"),
addressFragments)); TextUtils.join(System.getProperty("line.separator"),addressFragments));
}
}
private void deliverResultToReceiver(int resultCode, String message) {
Bundle bundle = new Bundle();
bundle.putString(Constants.RESULT_DATA_KEY, message);
mReceiver.send(resultCode, bundle);
}
}
and this is the MainAcitivty class in which I'm trying to fetch the address. Note that there is a private class AddressResultReceiver that extends ResultReciever too.
public class MainActivity extends Activity implements
ConnectionCallbacks, OnConnectionFailedListener, LocationListener{
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
latitudeText = (TextView) findViewById(R.id.latitudeText);
longitudeText = (TextView) findViewById(R.id.longitudeText);
lastUpdateTimeText = (TextView) findViewById(R.id.lastUpdateText);
buildGoogleApiClient();
}
protected void startIntentService() {
Intent intent = new Intent(this, FetchAddressIntentService.class);
intent.putExtra(Constants.RECEIVER, mResultReceiver);
intent.putExtra(Constants.LOCATION_DATA_EXTRA, mLastLocation);
startService(intent);
AddressResultReceiver ar = new AddressResultReceiver(null);
Bundle b = new Bundle();
ar.onReceiveResult(Constants.SUCCESS_RESULT, b);
}
protected synchronized void buildGoogleApiClient() {
mGoogleApiClient = new GoogleApiClient.Builder(this)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(LocationServices.API)
.build();
mGoogleApiClient.connect();
}
@SuppressLint("NewApi")
@Override
public void onConnected(Bundle connectionHint) {
Toast.makeText(this, "onConnected", Toast.LENGTH_LONG).show();
mLastLocation = LocationServices.FusedLocationApi.getLastLocation(
mGoogleApiClient);
if (mLastLocation != null) {
String latitude = String.valueOf(mLastLocation.getLatitude());
String longitude = String.valueOf(mLastLocation.getLongitude());
latitudeText.setText("latitude: " + latitude);
longitudeText.setText("longitude: " + longitude);
}
if (mLastLocation != null) {
// Determine whether a Geocoder is available.
if (!Geocoder.isPresent()) {
Toast.makeText(this, "No geocoder available",
Toast.LENGTH_LONG).show();
return;
}
if (mAddressRequested) {
startIntentService();
}
}
}
private void updateUI() {
latitudeText.setText(String.valueOf(mCurrentLocation.getLatitude()));
longitudeText.setText(String.valueOf(mCurrentLocation.getLongitude()));
lastUpdateTimeText.setText(mLastUpdateTime);
}
class AddressResultReceiver extends ResultReceiver {
public AddressResultReceiver(Handler handler) {
super(handler);
}
@Override
protected void onReceiveResult(int resultCode, Bundle resultData) {
// Display the address string
// or an error message sent from the intent service.
String mAddressOutput = resultData.getString(Constants.RESULT_DATA_KEY);
Log.e("RESULT!!!", mAddressOutput);
// Show a toast message if an address was found.
if (resultCode == Constants.SUCCESS_RESULT) {
;
}
}
}
}
I get a null-pointer exception, when i call the private method deliverResultToReciever. And it could be appreciated if you could show me how to fetch the address data properly
回答1:
Not initializing mResultReceiver object before passing to Intent Service.do it as:
protected void startIntentService() {
Intent intent = new Intent(this, FetchAddressIntentService.class);
mResultReceiver = new AddressResultReceiver(new Handler());
.... your code here
}
and also initialize mReceiver object in FetchAddressIntentService class by getting receiver in onHandleIntent method:
@Override
protected void onHandleIntent(Intent intent) {
mReceiver = intent.getParcelableExtra(Constants.RECEIVER);
//...your code here
}
来源：https://stackoverflow.com/questions/29215431/resultreceiver-gives-nullpointer-exception