调用具有NullPointerException权限的LocationUpdatesService时，应用程序崩溃 [英] App crashes while calling LocationUpdatesService with permission with NullPointerException
本文介绍了调用具有NullPointerException权限的LocationUpdatesService时，应用程序崩溃的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我正在尝试从 github 在我的应用程序中.在应用程序的第一次运行中，它运行良好.它请求位置许可，并且当用户授予许可时，该服务会完美启动并获取位置.
I' trying to implement Google's android foreground location sample from github in my application. It works fine in the first run of the application. It requests for location permission and when the user grants permission, the service is starting flawlessly and fetches location.
但是当应用程序已经具有权限时下次运行时，它会由于显示NullPointerException而崩溃.我无法缩小问题的范围.已获得许可的第二次运行的应用程序有何不同?在 mService.requestLocationUpdates(); 行的 OnStart()中出现错误.它必须对LocationUpdatesService中声明的包名称执行任何操作吗?还是经过许可的其他东西?或具有约束力?
But when the app runs the next time while it already has the permission, it crashes by showing a NullPointerException. I'm not able to narrow down the problem. What is different in the second run of the app which already has the permission? Getting error in OnStart() in mService.requestLocationUpdates(); line.
Does it has to do anything with the package name that is declared in the LocationUpdatesService? or is it something else with permission? or with binding?
Stacktrace
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;
}
}
推荐答案
我不确定，但是请尝试以下操作:
I am not sure, but try this:
@Override
protected void onStart() {
super.onStart();
PreferenceManager.getDefaultSharedPreferences(this)
.registerOnSharedPreferenceChangeListener(this);
if (!checkPermissions()) {
requestPermissions();
} else if (mService != null) { // add null checker
mService.requestLocationUpdates();
}
// 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);
}
也:
private final ServiceConnection mServiceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
LocationUpdatesService.LocalBinder binder = (LocationUpdatesService.LocalBinder) service;
mService = binder.getService();
mService.requestLocationUpdates(); // also request it here
mBound = true;
}
@Override
public void onServiceDisconnected(ComponentName name) {
mService = null;
mBound = false;
}
};
这篇关于调用具有NullPointerException权限的LocationUpdatesService时，应用程序崩溃的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
查看全文
