Christoph Jerolimov created CB-1578:
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Summary: App crash (while stopping) caused by an unregistered
notification handler in CDVConnection
Key: CB-1578
URL: https://issues.apache.org/jira/browse/CB-1578
Project: Apache Cordova
Issue Type: Bug
Components: iOS
Affects Versions: 2.0.0, 2.1.0
Environment: iOS, all versions
XCode, all versions
Reporter: Christoph Jerolimov
Assignee: Shazron Abdullah
Priority: Critical
The class {{CDVConnection}} registered itself as observer for background events
{{UIApplicationDidEnterBackgroundNotification}} and
{{UIApplicationWillEnterForegroundNotification}}. But it did NOT unregistered
these calls, for example in the dealloc method.
This caused in different type of errors which all ends in an app crash. If a
CDVConnection instance was already removed from the memory the selectors
onPause and onResume will be called on random other objects which doesn't
support this selector (1) or illegal memory access!
{code}
# Only an example, this error calls selectors on "random memory / objects"!
<Error>: -[CALayer onPause]: unrecognized selector sent to instance 0x1e56ac50
{code}
The code which register the notification could be found at the end of the file
in the selector {{[CDVConnection initWithWebView:]}}.
The versions 2.0.0 and 2.1.0 does NOT cleanup "only" the two mentioned events.
Like you see in line 139:
https://github.com/apache/incubator-cordova-ios/blob/2.0.0/CordovaLib/Classes/CDVConnection.m#L139
https://github.com/apache/incubator-cordova-ios/blob/2.1.0/CordovaLib/Classes/CDVConnection.m#L139
The current HEAD do additionally NOT remove the the event
{{kReachabilityChangedNotification}} from line 113 which should result in
another new bug in the upcoming version.
https://github.com/apache/incubator-cordova-ios/blob/master/CordovaLib/Classes/CDVConnection.m#L113
To fix this it's enough to add these removeObservers calls again to the dealloc
method.
{code}
[[NSNotificationCenter defaultCenter] removeObserver:self
name:kReachabilityChangedNotification object:nil];
[[NSNotificationCenter defaultCenter] removeObserver:self
name:UIApplicationDidEnterBackgroundNotification object:nil];
[[NSNotificationCenter defaultCenter] removeObserver:self
name:UIApplicationWillEnterForegroundNotification object:nil];
{code}
In generally it's would also be possible to remove the instance in CDVPlugin
for all events!? This would allow you to remove many code from many different
plugins and ensure that no other plugin forget these cleanup.
{code}
[[NSNotificationCenter defaultCenter] removeObserver:self];
{code}
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