使用NullPointerException权限调用LocationUpdatesService时应用程序崩溃

我正试图在我的应用程序中从github实现谷歌的android前台位置示例。它在应用程序的第一次运行中运行良好。它请求位置权限，当用户授予权限时，服务将完美启动并获取位置。

但是，当应用程序在已经拥有权限的情况下下次运行时，它会显示NullPointerException而崩溃。我无法缩小问题的范围。已经拥有权限的应用程序在第二次运行时有什么不同？在mService.requestLocationUpdates();行的OnStart()中获取错误。它与LocationUpdatesService中声明的包名称有任何关系吗？还是得到许可的其他东西？还是绑定？

堆栈跟踪

2020-10-21 11:58:04.346 31805-31805/com.example.testapp E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.testapp, PID: 31805
java.lang.NullPointerException: Attempt to invoke virtual method 'void com.example.testapp.LocationUpdatesService.requestLocationUpdates()' on a null object reference
at com.example.testapp.EventsActivity.onStart(EventsActivity.java:237)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1391)
at android.app.Activity.performStart(Activity.java:7348)
at android.app.ActivityThread.handleStartActivity(ActivityThread.java:3140)
at android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:180)
at 
android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:165)
at 
android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:142)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:70)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1950)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7073)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:494)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:965)
2020-10-21 11:58:04.367 31805-31805/com.example.testapp I/Process: Sending signal. PID: 31805 SIG: 9

MainActivity.java

public class MainActivity extends AppCompatActivity implements
SharedPreferences.OnSharedPreferenceChangeListener {

//Location
private static final String TAG = MainActivity.class.getSimpleName();
// Used in checking for runtime permissions.
private static final int REQUEST_PERMISSIONS_REQUEST_CODE = 34;
// The BroadcastReceiver used to listen from broadcasts from the service.
private MyReceiver myReceiver;
// A reference to the service used to get location updates.
private LocationUpdatesService mService = null;
// Tracks the bound state of the service.
private boolean mB
ound = false;
// Monitors the state of the connection to the service.
private final ServiceConnection mServiceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
LocationUpdatesService.LocalBinder binder = (LocationUpdatesService.LocalBinder) service;
mService = binder.getService();
mBound = true;
}
@Override
public void onServiceDisconnected(ComponentName name) {
mService = null;
mBound = false;
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
myReceiver = new MyReceiver();
// Check that the user hasn't revoked permissions by going to Settings.
if (Utils.requestingLocationUpdates(this)) {
if (!checkPermissions()) {
requestPermissions();
}
}
....
.....
}

@Override
protected void onStart() {
super.onStart();
PreferenceManager.getDefaultSharedPreferences(this)
.registerOnSharedPreferenceChangeListener(this);
if (!checkPermissions()) {
requestPermissions();
} else {
mService.requestLocationUpdates(); //CRASHING HERE
}
// Bind to the service. If the service is in foreground mode, this signals to the service
// that since this activity is in the foreground, the service can exit foreground mode.
bindService(new Intent(this, LocationUpdatesService.class), mServiceConnection,
Context.BIND_AUTO_CREATE);
}
@Override
protected void onStop() {
if (mBound) {
// Unbind from the service. This signals to the service that this activity is no longer
// in the foreground, and the service can respond by promoting itself to a foreground
// service.
unbindService(mServiceConnection);
mBound = false;
}
PreferenceManager.getDefaultSharedPreferences(this)
.unregisterOnSharedPreferenceChangeListener(this);
super.onStop();
}
/**
* Returns the current state of the permissions needed.
*/
private boolean checkPermissions() {
return  PackageManager.PERMISSION_GRANTED == ActivityCompat.checkSelfPermission(this,
Manifest.permission.ACCESS_FINE_LOCATION);
}
private void requestPermissions() {
boolean shouldProvideRationale =
ActivityCompat.shouldShowRequestPermissionRationale(this,
Manifest.permission.ACCESS_FINE_LOCATION);
// Provide an additional rationale to the user. This would happen if the user denied the
// request previously, but didn't check the "Don't ask again" checkbox.
if (shouldProvideRationale) {
Log.i(TAG, "Displaying permission rationale to provide additional context.");
Snackbar.make(
findViewById(R.id.sliding_layout),
R.string.permission_rationale,
Snackbar.LENGTH_INDEFINITE)
.setAction(R.string.ok, new View.OnClickListener() {
@Override
public void onClick(View view) {
// Request permission
ActivityCompat.requestPermissions(MainActivity.this,
new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
REQUEST_PERMISSIONS_REQUEST_CODE);
}
})
.show();
} else {
Log.i(TAG, "Requesting permission");
// Request permission. It's possible this can be auto answered if device policy
// sets the permission in a given state or the user denied the permission
// previously and checked "Never ask again".
ActivityCompat.requestPermissions(MainActivity.this,
new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
REQUEST_PERMISSIONS_REQUEST_CODE);
}
}
/**
* Callback received when a permissions request has been completed.
*/
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,
@NonNull int[] grantResults) {
Log.i(TAG, "onRequestPermissionResult");
if (requestCode == REQUEST_PERMISSIONS_REQUEST_CODE) {
if (grantResults.length <= 0) {
// If user interaction was interrupted, the permission request is cancelled and you
// receive empty arrays.
Log.i(TAG, "User interaction was cancelled.");
} else if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// Permission was granted.
mService.requestLocationUpdates();
} else {
// Permission denied.
//setButtonsState(false);
Snackbar.make(
findViewById(R.id.sliding_layout),
R.string.permission_denied_explanation,
Snackbar.LENGTH_INDEFINITE)
.setAction(R.string.settings, new View.OnClickListener() {
@Override
public void onClick(View view) {
// Build intent that displays the App settings screen.
Intent intent = new Intent();
intent.setAction(
Settings.ACTION_APPLICATION_DETAILS_SETTINGS);
Uri uri = Uri.fromParts("package",
BuildConfig.APPLICATION_ID, null);
intent.setData(uri);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);
}
})
.show();
}
}
}
/**
* Receiver for broadcasts sent by {@link LocationUpdatesService}.
*/
private class MyReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
Location location = intent.getParcelableExtra(LocationUpdatesService.EXTRA_LOCATION);
if (location != null) {
Toast.makeText(MainActivity.this, Utils.getLocationText(location),
Toast.LENGTH_SHORT).show();
}
}
}
@Override
public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String s) {
}


@Override
protected void onResume() {
LocalBroadcastManager.getInstance(this).registerReceiver(myReceiver,
new IntentFilter(LocationUpdatesService.ACTION_BROADCAST));
super.onResume();
wakeLock.acquire();
}
@Override
protected void onPause() {
LocalBroadcastManager.getInstance(this).unregisterReceiver(myReceiver);
super.onPause();
}
@Override
public void onDestroy() {
super.onDestroy();
if(getBooleanFromSP("logOutBtnClicked")){
stopService();
mService.removeLocationUpdates();
}else if(!getBooleanFromSP("logOutBtnClicked")){
startService();
mService.removeLocationUpdates();
}
}
}

LocationUpdatesService.java

public class LocationUpdatesService extends Service {
private static final String PACKAGE_NAME =
"com.google.android.gms.location.sample.locationupdatesforegroundservice";
private static final String TAG = LocationUpdatesService.class.getSimpleName();
/**
* The name of the channel for notifications.
*/
private static final String CHANNEL_ID = "channel_01";
static final String ACTION_BROADCAST = PACKAGE_NAME + ".broadcast";
static final String EXTRA_LOCATION = PACKAGE_NAME + ".location";
private static final String EXTRA_STARTED_FROM_NOTIFICATION = PACKAGE_NAME +
".started_from_notification";
private final IBinder mBinder = new LocalBinder();
/**
* The desired interval for location updates. Inexact. Updates may be more or less frequent.
*/
private static final long UPDATE_INTERVAL_IN_MILLISECONDS = 10000;
/**
* The fastest rate for active location updates. Updates will never be more frequent
* than this value.
*/
private static final long FASTEST_UPDATE_INTERVAL_IN_MILLISECONDS =
UPDATE_INTERVAL_IN_MILLISECONDS / 2;
/**
* The identifier for the notification displayed for the foreground service.
*/
private static final int NOTIFICATION_ID = 12345678;
/**
* Used to check whether the bound activity has really gone away and not unbound as part of an
* orientation change. We create a foreground service notification only if the former takes
* place.
*/
private boolean mChangingConfiguration = false;
private NotificationManager mNotificationManager;
/**
* Contains parameters used by {@link com.google.android.gms.location.FusedLocationProviderApi}.
*/
private LocationRequest mLocationRequest;
/**
* Provides access to the Fused Location Provider API.
*/
private FusedLocationProviderClient mFusedLocationClient;
/**
* Callback for changes in location.
*/
private LocationCallback mLocationCallback;
private Handler mServiceHandler;
/**
* The current location.
*/
private Location mLocation;
public LocationUpdatesService() {
}
@Override
public void onCreate() {
mFusedLocationClient = LocationServices.getFusedLocationProviderClient(this);
mLocationCallback = new LocationCallback() {
@Override
public void onLocationResult(LocationResult locationResult) {
super.onLocationResult(locationResult);
onNewLocation(locationResult.getLastLocation());
}
};
createLocationRequest();
getLastLocation();
HandlerThread handlerThread = new HandlerThread(TAG);
handlerThread.start();
mServiceHandler = new Handler(handlerThread.getLooper());
mNotificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
// Android O requires a Notification Channel.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
CharSequence name = getString(R.string.app_name);
// Create the channel for the notification
NotificationChannel mChannel =
new NotificationChannel(CHANNEL_ID, name, NotificationManager.IMPORTANCE_DEFAULT);
// Set the Notification Channel for the Notification Manager.
mNotificationManager.createNotificationChannel(mChannel);
}
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
Log.i(TAG, "Service started");
boolean startedFromNotification = intent.getBooleanExtra(EXTRA_STARTED_FROM_NOTIFICATION,
false);
// We got here because the user decided to remove location updates from the notification.
if (startedFromNotification) {
removeLocationUpdates();
stopSelf();
}
// Tells the system to not try to recreate the service after it has been killed.
return START_NOT_STICKY;
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
mChangingConfiguration = true;
}
@Override
public IBinder onBind(Intent intent) {
// Called when a client (MainActivity in case of this sample) comes to the foreground
// and binds with this service. The service should cease to be a foreground service
// when that happens.
Log.i(TAG, "in onBind()");
stopForeground(true);
mChangingConfiguration = false;
return mBinder;
}
@Override
public void onRebind(Intent intent) {
// Called when a client (MainActivity in case of this sample) returns to the foreground
// and binds once again with this service. The service should cease to be a foreground
// service when that happens.
Log.i(TAG, "in onRebind()");
stopForeground(true);
mChangingConfiguration = false;
super.onRebind(intent);
}
@Override
public boolean onUnbind(Intent intent) {
Log.i(TAG, "Last client unbound from service");
// Called when the last client (MainActivity in case of this sample) unbinds from this
// service. If this method is called due to a configuration change in MainActivity, we
// do nothing. Otherwise, we make this service a foreground service.
if (!mChangingConfiguration && Utils.requestingLocationUpdates(this)) {
Log.i(TAG, "Starting foreground service");
startForeground(NOTIFICATION_ID, getNotification());
}
return true; // Ensures onRebind() is called when a client re-binds.
}
@Override
public void onDestroy() {
mServiceHandler.removeCallbacksAndMessages(null);
}
/**
* Makes a request for location updates. Note that in this sample we merely log the
* {@link SecurityException}.
*/
public void requestLocationUpdates() {
Log.i(TAG, "Requesting location updates");
Utils.setRequestingLocationUpdates(this, true);
startService(new Intent(getApplicationContext(), LocationUpdatesService.class));
try {
mFusedLocationClient.requestLocationUpdates(mLocationRequest,
mLocationCallback, Looper.myLooper());
} catch (SecurityException unlikely) {
Utils.setRequestingLocationUpdates(this, false);
Log.e(TAG, "Lost location permission. Could not request updates. " + unlikely);
}
}
/**
* Removes location updates. Note that in this sample we merely log the
* {@link SecurityException}.
*/
public void removeLocationUpdates() {
Log.i(TAG, "Removing location updates");
try {
mFusedLocationClient.removeLocationUpdates(mLocationCallback);
Utils.setRequestingLocationUpdates(this, false);
stopSelf();
} catch (SecurityException unlikely) {
Utils.setRequestingLocationUpdates(this, true);
Log.e(TAG, "Lost location permission. Could not remove updates. " + unlikely);
}
}
/**
* Returns the {@link NotificationCompat} used as part of the foreground service.
*/
private Notification getNotification() {
Intent intent = new Intent(this, LocationUpdatesService.class);
CharSequence text = Utils.getLocationText(mLocation);
// Extra to help us figure out if we arrived in onStartCommand via the notification or not.
intent.putExtra(EXTRA_STARTED_FROM_NOTIFICATION, true);
// The PendingIntent that leads to a call to onStartCommand() in this service.
PendingIntent servicePendingIntent = PendingIntent.getService(this, 0, intent,
PendingIntent.FLAG_UPDATE_CURRENT);
// The PendingIntent to launch activity.
PendingIntent activityPendingIntent = PendingIntent.getActivity(this, 0,
new Intent(this, EventsActivity.class), 0);
NotificationCompat.Builder builder = new NotificationCompat.Builder(this)
.addAction(R.drawable.ic_launch, getString(R.string.launch_activity),
activityPendingIntent)
.addAction(R.drawable.ic_cancel, getString(R.string.remove_location_updates),
servicePendingIntent)
.setContentText(text)
.setContentTitle(Utils.getLocationTitle(this))
.setOngoing(true)
.setPriority(Notification.PRIORITY_HIGH)
.setSmallIcon(R.mipmap.ic_launcher)
.setTicker(text)
.setWhen(System.currentTimeMillis());
// Set the Channel ID for Android O.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
builder.setChannelId(CHANNEL_ID); // Channel ID
}
return builder.build();
}
private void getLastLocation() {
try {
mFusedLocationClient.getLastLocation()
.addOnCompleteListener(new OnCompleteListener<Location>() {
@Override
public void onComplete(@NonNull Task<Location> task) {
if (task.isSuccessful() && task.getResult() != null) {
mLocation = task.getResult();
} else {
Log.w(TAG, "Failed to get location.");
}
}
});
} catch (SecurityException unlikely) {
Log.e(TAG, "Lost location permission." + unlikely);
}
}
private void onNewLocation(Location location) {
Log.i(TAG, "New location: " + location);
mLocation = location;
// Notify anyone listening for broadcasts about the new location.
Intent intent = new Intent(ACTION_BROADCAST);
intent.putExtra(EXTRA_LOCATION, location);
LocalBroadcastManager.getInstance(getApplicationContext()).sendBroadcast(intent);
// Update notification content if running as a foreground service.
if (serviceIsRunningInForeground(this)) {
mNotificationManager.notify(NOTIFICATION_ID, getNotification());
}
}
/**
* Sets the location request parameters.
*/
private void createLocationRequest() {
mLocationRequest = new LocationRequest();
mLocationRequest.setInterval(UPDATE_INTERVAL_IN_MILLISECONDS);
mLocationRequest.setFastestInterval(FASTEST_UPDATE_INTERVAL_IN_MILLISECONDS);
mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
}
/**
* Class used for the client Binder.  Since this service runs in the same process as its
* clients, we don't need to deal with IPC.
*/
public class LocalBinder extends Binder {
LocationUpdatesService getService() {
return LocationUpdatesService.this;
}
}
/**
* Returns true if this is a foreground service.
*
* @param context The {@link Context}.
*/
public boolean serviceIsRunningInForeground(Context context) {
ActivityManager manager = (ActivityManager) context.getSystemService(
Context.ACTIVITY_SERVICE);
for (ActivityManager.RunningServiceInfo service : manager.getRunningServices(
Integer.MAX_VALUE)) {
if (getClass().getName().equals(service.service.getClassName())) {
if (service.foreground) {
return true;
}
}
}
return false;
}
}