无法直接复制Google的LocationUpdates培训示例。 NullPointerException如下所示。
代码与Google的代码相同：http://developer.android.com/training/location/retrieve-current.html
12-18 00:23:41.776 21601-21601/com.neil.practice E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.NullPointerException
at com.neil.practice.google.geo.MainActivity.onConnected(MainActivity.java:366)
at com.google.android.gms.internal.p.k(Unknown Source)
at com.google.android.gms.internal.p$f.a(Unknown Source)
at com.google.android.gms.internal.p$f.a(Unknown Source)
at com.google.android.gms.internal.p$b.p(Unknown Source)
at com.google.android.gms.internal.p$a.handleMessage(Unknown Source)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4950)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1004)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:771)
at dalvik.system.NativeStart.main(Native Method)
更新1 ：轻松发布MainActivity.java代码
package com.example.android.location;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesClient;
import com.google.android.gms.common.GooglePlayServicesUtil;
import com.google.android.gms.location.LocationClient;
import com.google.android.gms.location.LocationListener;
import com.google.android.gms.location.LocationRequest;
import android.content.IntentSender;
import android.location.Address;
import android.location.Geocoder;
import android.location.Location;
import android.os.AsyncTask;
import android.os.Build;
import android.os.Bundle;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.app.Dialog;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.support.v4.app.DialogFragment;
import android.support.v4.app.FragmentActivity;
import android.util.Log;
import android.view.View;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;
import java.io.IOException;
import java.util.List;
import java.util.Locale;
/**
* This the app's main Activity. It provides buttons for requesting the various features of the
* app, displays the current location, the current address, and the status of the location client
* and updating services.
*
* {@link #getLocation} gets the current location using the Location Services getLastLocation()
* function. {@link #getAddress} calls geocoding to get a street address for the current location.
* {@link #startUpdates} sends a request to Location Services to send periodic location updates to
* the Activity.
* {@link #stopUpdates} cancels previous periodic update requests.
*
* The update interval is hard-coded to be 5 seconds.
*/
public class MainActivity extends FragmentActivity implements
LocationListener,
GooglePlayServicesClient.ConnectionCallbacks,
GooglePlayServicesClient.OnConnectionFailedListener {
// A request to connect to Location Services
private LocationRequest mLocationRequest;
// Stores the current instantiation of the location client in this object
private LocationClient mLocationClient;
// Handles to UI widgets
private TextView mLatLng;
private TextView mAddress;
private ProgressBar mActivityIndicator;
private TextView mConnectionState;
private TextView mConnectionStatus;
// Handle to SharedPreferences for this app
SharedPreferences mPrefs;
// Handle to a SharedPreferences editor
SharedPreferences.Editor mEditor;
/*
* Note if updates have been turned on. Starts out as "false"; is set to "true" in the
* method handleRequestSuccess of LocationUpdateReceiver.
*
*/
boolean mUpdatesRequested = false;
/*
* Initialize the Activity
*/
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Get handles to the UI view objects
mLatLng = (TextView) findViewById(R.id.lat_lng);
mAddress = (TextView) findViewById(R.id.address);
mActivityIndicator = (ProgressBar) findViewById(R.id.address_progress);
mConnectionState = (TextView) findViewById(R.id.text_connection_state);
mConnectionStatus = (TextView) findViewById(R.id.text_connection_status);
// Create a new global location parameters object
mLocationRequest = LocationRequest.create();
/*
* Set the update interval
*/
mLocationRequest.setInterval(LocationUtils.UPDATE_INTERVAL_IN_MILLISECONDS);
// Use high accuracy
mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
// Set the interval ceiling to one minute
mLocationRequest.setFastestInterval(LocationUtils.FAST_INTERVAL_CEILING_IN_MILLISECONDS);
// Note that location updates are off until the user turns them on
mUpdatesRequested = false;
// Open Shared Preferences
mPrefs = getSharedPreferences(LocationUtils.SHARED_PREFERENCES, Context.MODE_PRIVATE);
// Get an editor
mEditor = mPrefs.edit();
/*
* Create a new location client, using the enclosing class to
* handle callbacks.
*/
mLocationClient = new LocationClient(this, this, this);
}
/*
* Called when the Activity is no longer visible at all.
* Stop updates and disconnect.
*/
@Override
public void onStop() {
// If the client is connected
if (mLocationClient.isConnected()) {
stopPeriodicUpdates();
}
// After disconnect() is called, the client is considered "dead".
mLocationClient.disconnect();
super.onStop();
}
/*
* Called when the Activity is going into the background.
* Parts of the UI may be visible, but the Activity is inactive.
*/
@Override
public void onPause() {
// Save the current setting for updates
mEditor.putBoolean(LocationUtils.KEY_UPDATES_REQUESTED, mUpdatesRequested);
mEditor.commit();
super.onPause();
}
/*
* Called when the Activity is restarted, even before it becomes visible.
*/
@Override
public void onStart() {
super.onStart();
/*
* Connect the client. Don't re-start any requests here;
* instead, wait for onResume()
*/
mLocationClient.connect();
}
/*
* Called when the system detects that this Activity is now visible.
*/
@Override
public void onResume() {
super.onResume();
// If the app already has a setting for getting location updates, get it
if (mPrefs.contains(LocationUtils.KEY_UPDATES_REQUESTED)) {
mUpdatesRequested = mPrefs.getBoolean(LocationUtils.KEY_UPDATES_REQUESTED, false);
// Otherwise, turn off location updates until requested
} else {
mEditor.putBoolean(LocationUtils.KEY_UPDATES_REQUESTED, false);
mEditor.commit();
}
}
/*
* Handle results returned to this Activity by other Activities started with
* startActivityForResult(). In particular, the method onConnectionFailed() in
* LocationUpdateRemover and LocationUpdateRequester may call startResolutionForResult() to
* start an Activity that handles Google Play services problems. The result of this
* call returns here, to onActivityResult.
*/
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent intent) {
// Choose what to do based on the request code
switch (requestCode) {
// If the request code matches the code sent in onConnectionFailed
case LocationUtils.CONNECTION_FAILURE_RESOLUTION_REQUEST :
switch (resultCode) {
// If Google Play services resolved the problem
case Activity.RESULT_OK:
// Log the result
Log.d(LocationUtils.APPTAG, getString(R.string.resolved));
// Display the result
mConnectionState.setText(R.string.connected);
mConnectionStatus.setText(R.string.resolved);
break;
// If any other result was returned by Google Play services
default:
// Log the result
Log.d(LocationUtils.APPTAG, getString(R.string.no_resolution));
// Display the result
mConnectionState.setText(R.string.disconnected);
mConnectionStatus.setText(R.string.no_resolution);
break;
}
// If any other request code was received
default:
// Report that this Activity received an unknown requestCode
Log.d(LocationUtils.APPTAG,
getString(R.string.unknown_activity_request_code, requestCode));
break;
}
}
/**
* Verify that Google Play services is available before making a request.
*
* @return true if Google Play services is available, otherwise false
*/
private boolean servicesConnected() {
// Check that Google Play services is available
int resultCode =
GooglePlayServicesUtil.isGooglePlayServicesAvailable(this);
// If Google Play services is available
if (ConnectionResult.SUCCESS == resultCode) {
// In debug mode, log the status
Log.d(LocationUtils.APPTAG, getString(R.string.play_services_available));
// Continue
return true;
// Google Play services was not available for some reason
} else {
// Display an error dialog
Dialog dialog = GooglePlayServicesUtil.getErrorDialog(resultCode, this, 0);
if (dialog != null) {
ErrorDialogFragment errorFragment = new ErrorDialogFragment();
errorFragment.setDialog(dialog);
errorFragment.show(getSupportFragmentManager(), LocationUtils.APPTAG);
}
return false;
}
}
/**
* Invoked by the "Get Location" button.
*
* Calls getLastLocation() to get the current location
*
* @param v The view object associated with this method, in this case a Button.
*/
public void getLocation(View v) {
// If Google Play Services is available
if (servicesConnected()) {
// Get the current location
Location currentLocation = mLocationClient.getLastLocation();
// Display the current location in the UI
mLatLng.setText(LocationUtils.getLatLng(this, currentLocation));
}
}
/**
* Invoked by the "Get Address" button.
* Get the address of the current location, using reverse geocoding. This only works if
* a geocoding service is available.
*
* @param v The view object associated with this method, in this case a Button.
*/
// For Eclipse with ADT, suppress warnings about Geocoder.isPresent()
@SuppressLint("NewApi")
public void getAddress(View v) {
// In Gingerbread and later, use Geocoder.isPresent() to see if a geocoder is available.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.GINGERBREAD && !Geocoder.isPresent()) {
// No geocoder is present. Issue an error message
Toast.makeText(this, R.string.no_geocoder_available, Toast.LENGTH_LONG).show();
return;
}
if (servicesConnected()) {
// Get the current location
Location currentLocation = mLocationClient.getLastLocation();
// Turn the indefinite activity indicator on
mActivityIndicator.setVisibility(View.VISIBLE);
// Start the background task
(new MainActivity.GetAddressTask(this)).execute(currentLocation);
}
}
/**
* Invoked by the "Start Updates" button
* Sends a request to start location updates
*
* @param v The view object associated with this method, in this case a Button.
*/
public void startUpdates(View v) {
mUpdatesRequested = true;
if (servicesConnected()) {
startPeriodicUpdates();
}
}
/**
* Invoked by the "Stop Updates" button
* Sends a request to remove location updates
* request them.
*
* @param v The view object associated with this method, in this case a Button.
*/
public void stopUpdates(View v) {
mUpdatesRequested = false;
if (servicesConnected()) {
stopPeriodicUpdates();
}
}
/*
* Called by Location Services when the request to connect the
* client finishes successfully. At this point, you can
* request the current location or start periodic updates
*/
@Override
public void onConnected(Bundle bundle) {
mConnectionStatus.setText(R.string.connected);
if (mUpdatesRequested) {
startPeriodicUpdates();
}
}
/*
* Called by Location Services if the connection to the
* location client drops because of an error.
*/
@Override
public void onDisconnected() {
mConnectionStatus.setText(R.string.disconnected);
}
/*
* Called by Location Services if the attempt to
* Location Services fails.
*/
@Override
public void onConnectionFailed(ConnectionResult connectionResult) {
/*
* Google Play services can resolve some errors it detects.
* If the error has a resolution, try sending an Intent to
* start a Google Play services activity that can resolve
* error.
*/
if (connectionResult.hasResolution()) {
try {
// Start an Activity that tries to resolve the error
connectionResult.startResolutionForResult(
this,
LocationUtils.CONNECTION_FAILURE_RESOLUTION_REQUEST);
/*
* Thrown if Google Play services canceled the original
* PendingIntent
*/
} catch (IntentSender.SendIntentException e) {
// Log the error
e.printStackTrace();
}
} else {
// If no resolution is available, display a dialog to the user with the error.
showErrorDialog(connectionResult.getErrorCode());
}
}
/**
* Report location updates to the UI.
*
* @param location The updated location.
*/
@Override
public void onLocationChanged(Location location) {
// Report to the UI that the location was updated
mConnectionStatus.setText(R.string.location_updated);
// In the UI, set the latitude and longitude to the value received
mLatLng.setText(LocationUtils.getLatLng(this, location));
}
/**
* In response to a request to start updates, send a request
* to Location Services
*/
private void startPeriodicUpdates() {
mLocationClient.requestLocationUpdates(mLocationRequest, this);
mConnectionState.setText(R.string.location_requested);
}
/**
* In response to a request to stop updates, send a request to
* Location Services
*/
private void stopPeriodicUpdates() {
mLocationClient.removeLocationUpdates(this);
mConnectionState.setText(R.string.location_updates_stopped);
}
/**
* An AsyncTask that calls getFromLocation() in the background.
* The class uses the following generic types:
* Location - A {@link android.location.Location} object containing the current location,
* passed as the input parameter to doInBackground()
* Void - indicates that progress units are not used by this subclass
* String - An address passed to onPostExecute()
*/
protected class GetAddressTask extends AsyncTask<Location, Void, String> {
// Store the context passed to the AsyncTask when the system instantiates it.
Context localContext;
// Constructor called by the system to instantiate the task
public GetAddressTask(Context context) {
// Required by the semantics of AsyncTask
super();
// Set a Context for the background task
localContext = context;
}
/**
* Get a geocoding service instance, pass latitude and longitude to it, format the returned
* address, and return the address to the UI thread.
*/
@Override
protected String doInBackground(Location... params) {
/*
* Get a new geocoding service instance, set for localized addresses. This example uses
* android.location.Geocoder, but other geocoders that conform to address standards
* can also be used.
*/
Geocoder geocoder = new Geocoder(localContext, Locale.getDefault());
// Get the current location from the input parameter list
Location location = params[0];
// Create a list to contain the result address
List <Address> addresses = null;
// Try to get an address for the current location. Catch IO or network problems.
try {
/*
* Call the synchronous getFromLocation() method with the latitude and
* longitude of the current location. Return at most 1 address.
*/
addresses = geocoder.getFromLocation(location.getLatitude(),
location.getLongitude(), 1
);
// Catch network or other I/O problems.
} catch (IOException exception1) {
// Log an error and return an error message
Log.e(LocationUtils.APPTAG, getString(R.string.IO_Exception_getFromLocation));
// print the stack trace
exception1.printStackTrace();
// Return an error message
return (getString(R.string.IO_Exception_getFromLocation));
// Catch incorrect latitude or longitude values
} catch (IllegalArgumentException exception2) {
// Construct a message containing the invalid arguments
String errorString = getString(
R.string.illegal_argument_exception,
location.getLatitude(),
location.getLongitude()
);
// Log the error and print the stack trace
Log.e(LocationUtils.APPTAG, errorString);
exception2.printStackTrace();
//
return errorString;
}
// If the reverse geocode returned an address
if (addresses != null && addresses.size() > 0) {
// Get the first address
Address address = addresses.get(0);
// Format the first line of address
String addressText = getString(R.string.address_output_string,
// If there's a street address, add it
address.getMaxAddressLineIndex() > 0 ?
address.getAddressLine(0) : "",
// Locality is usually a city
address.getLocality(),
// The country of the address
address.getCountryName()
);
// Return the text
return addressText;
// If there aren't any addresses, post a message
} else {
return getString(R.string.no_address_found);
}
}
/**
* A method that's called once doInBackground() completes. Set the text of the
* UI element that displays the address. This method runs on the UI thread.
*/
@Override
protected void onPostExecute(String address) {
// Turn off the progress bar
mActivityIndicator.setVisibility(View.GONE);
// Set the address in the UI
mAddress.setText(address);
}
}
/**
* Show a dialog returned by Google Play services for the
* connection error code
*
* @param errorCode An error code returned from onConnectionFailed
*/
private void showErrorDialog(int errorCode) {
// Get the error dialog from Google Play services
Dialog errorDialog = GooglePlayServicesUtil.getErrorDialog(
errorCode,
this,
LocationUtils.CONNECTION_FAILURE_RESOLUTION_REQUEST);
// If Google Play services can provide an error dialog
if (errorDialog != null) {
// Create a new DialogFragment in which to show the error dialog
ErrorDialogFragment errorFragment = new ErrorDialogFragment();
// Set the dialog in the DialogFragment
errorFragment.setDialog(errorDialog);
// Show the error dialog in the DialogFragment
errorFragment.show(getSupportFragmentManager(), LocationUtils.APPTAG);
}
}
/**
* Define a DialogFragment to display the error dialog generated in
* showErrorDialog.
*/
public static class ErrorDialogFragment extends DialogFragment {
// Global field to contain the error dialog
private Dialog mDialog;
/**
* Default constructor. Sets the dialog field to null
*/
public ErrorDialogFragment() {
super();
mDialog = null;
}
/**
* Set the dialog to display
*
* @param dialog An error dialog
*/
public void setDialog(Dialog dialog) {
mDialog = dialog;
}
/*
* This method must return a Dialog to the DialogFragment.
*/
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
return mDialog;
}
}
}