问题
UPDATE 2
My app is crashing when presenting it modally after a user taps a button in ViewController1. In my storyboard, I have a standard present modally segue set to pop up the UINavController/UITableViewController containing the UISearchBar. That's failing every time.
However, in my AppDelegate, if I set the window's rootViewController to the same UINavController/UITableViewController, everything works as expected.
For some reason transitioning via segue and then acting the UISearchBar is causing the crash.
UPDATE 1
I'm now receiving the following error when tapping one letter:
2015-02-03 12:23:35.262 Afar D[28348:2740681] -[NSNull length]: unrecognized selector sent to instance 0x10e352ce0
2015-02-03 12:23:40.313 Afar D[28348:2740681] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSNull length]: unrecognized selector sent to instance 0x10e352ce0'
*** First throw call stack:
(
0 CoreFoundation 0x000000010e0a9f35 __exceptionPreprocess + 165
1 libobjc.A.dylib 0x000000010dd42bb7 objc_exception_throw + 45
2 CoreFoundation 0x000000010e0b104d -[NSObject(NSObject) doesNotRecognizeSelector:] + 205
3 CoreFoundation 0x000000010e00927c ___forwarding___ + 988
4 CoreFoundation 0x000000010e008e18 _CF_forwarding_prep_0 + 120
5 CoreFoundation 0x000000010df89a7b CFStringCompareWithOptionsAndLocale + 219
6 Foundation 0x000000010d6822b7 -[NSString compare:options:range:] + 29
7 UIKit 0x000000010c5f53b4 -[UIPhysicalKeyboardEvent _matchesKeyCommand:] + 224
8 UIKit 0x000000010c53c12e -[UIResponder(Internal) _keyCommandForEvent:] + 285
9 UIKit 0x000000010c53c197 -[UIResponder(Internal) _keyCommandForEvent:] + 390
10 UIKit 0x000000010c53c197 -[UIResponder(Internal) _keyCommandForEvent:] + 390
11 UIKit 0x000000010c53c197 -[UIResponder(Internal) _keyCommandForEvent:] + 390
12 UIKit 0x000000010c53c197 -[UIResponder(Internal) _keyCommandForEvent:] + 390
13 UIKit 0x000000010c53c197 -[UIResponder(Internal) _keyCommandForEvent:] + 390
14 UIKit 0x000000010c53c197 -[UIResponder(Internal) _keyCommandForEvent:] + 390
15 UIKit 0x000000010c53c197 -[UIResponder(Internal) _keyCommandForEvent:] + 390
16 UIKit 0x000000010c3d8f0a -[UIApplication _handleKeyUIEvent:] + 126
17 UIKit 0x000000010c5c7fcc -[UIKeyboardImpl _handleKeyEvent:executionContext:] + 66
18 UIKit 0x000000010c75bbb7 -[UIKeyboardLayoutStar completeRetestForTouchUp:timestamp:interval:executionContext:] + 3611
19 UIKit 0x000000010c75a8e5 -[UIKeyboardLayoutStar touchUp:executionContext:] + 1374
20 UIKit 0x000000010c5d531b __28-[UIKeyboardLayout touchUp:]_block_invoke + 242
21 UIKit 0x000000010cb23914 -[UIKeyboardTaskQueue continueExecutionOnMainThread] + 332
22 UIKit 0x000000010c5d521c -[UIKeyboardLayout touchUp:] + 252
23 UIKit 0x000000010c5d5cc6 -[UIKeyboardLayout touchesEnded:withEvent:] + 319
24 UIKit 0x000000010c40b308 -[UIWindow _sendTouchesForEvent:] + 735
25 UIKit 0x000000010c40bc33 -[UIWindow sendEvent:] + 683
26 UIKit 0x000000010c3d89b1 -[UIApplication sendEvent:] + 246
27 UIKit 0x000000010c3e5a7d _UIApplicationHandleEventFromQueueEvent + 17370
28 UIKit 0x000000010c3c1103 _UIApplicationHandleEventQueue + 1961
29 CoreFoundation 0x000000010dfdf551 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
30 CoreFoundation 0x000000010dfd541d __CFRunLoopDoSources0 + 269
31 CoreFoundation 0x000000010dfd4a54 __CFRunLoopRun + 868
32 CoreFoundation 0x000000010dfd4486 CFRunLoopRunSpecific + 470
33 GraphicsServices 0x000000010fc109f0 GSEventRunModal + 161
34 UIKit 0x000000010c3c4420 UIApplicationMain + 1282
35 My App 0x000000010a5e1c63 main + 115
36 libdyld.dylib 0x000000010e75a145 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
I'm using iOS8's new UISearchController to manage a UISearchBar for filtering data in a table. If I activate the UISearchBar, the app crashes as soon as I type the first letter (Interestingly, the on-screen keyboard doesn't appear in the Simulator, but I don't think that's related).
In order to narrow things down, I've commented almost everything out of my UIViewController so that the UITableView renders nothing. I've implemented UISearchControllerDelegate and UISearchBarDelegate just so I can log when each method gets called. However, after typing the first letter, I receive no console messages. I don't even know where I could set a breakpoint.
Here's the crash I get:
-[NSNull length]: unrecognized selector sent to instance 0x107602ce0
Note that nowhere in my file am I calling length on anything. Something behind the scenes is, but I can't figure out what.
Here's my code to set up the UISearchController:
- (void)viewDidLoad
{
[super viewDidLoad];
self.searchController = [[UISearchController alloc] initWithSearchResultsController:nil];
self.searchController.searchResultsUpdater = self;
self.searchController.definesPresentationContext = true;
self.searchController.hidesNavigationBarDuringPresentation = false;
[self.searchController.searchBar sizeToFit];
self.tableView.tableHeaderView = self.searchController.searchBar;
self.searchController.searchBar.delegate = self;
self.searchController.delegate = self;
}
By request, here are my delegate methods (implemented just to see if anything gets called after typing the first letter - they don't):
#pragma mark - UISearchResultsUpdating
- (void)updateSearchResultsForSearchController:(UISearchController *)searchController
{
NSLog(@"%s", __PRETTY_FUNCTION__);
}
#pragma mark - UISearchControllerDelegate
- (void)didDismissSearchController:(UISearchController *)searchController
{
NSLog(@"%s", __PRETTY_FUNCTION__);
}
- (void)didPresentSearchController:(UISearchController *)searchController
{
NSLog(@"%s", __PRETTY_FUNCTION__);
}
- (void)presentSearchController:(UISearchController *)searchController
{
NSLog(@"%s", __PRETTY_FUNCTION__);
}
- (void)willDismissSearchController:(UISearchController *)searchController
{
NSLog(@"%s", __PRETTY_FUNCTION__);
}
- (void)willPresentSearchController:(UISearchController *)searchController
{
NSLog(@"%s", __PRETTY_FUNCTION__);
}
#pragma mark - UISearchBarDelegate
- (void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText
{
NSLog(@"%s", __PRETTY_FUNCTION__);
}
- (BOOL)searchBar:(UISearchBar *)searchBar shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{
NSLog(@"%s", __PRETTY_FUNCTION__);
return true;
}
- (BOOL)searchBarShouldBeginEditing:(UISearchBar *)searchBar
{
NSLog(@"%s", __PRETTY_FUNCTION__);
return true;
}
- (void)searchBarTextDidBeginEditing:(UISearchBar *)searchBar
{
NSLog(@"%s", __PRETTY_FUNCTION__);
}
- (BOOL)searchBarShouldEndEditing:(UISearchBar *)searchBar
{
NSLog(@"%s", __PRETTY_FUNCTION__);
return true;
}
- (void)searchBarTextDidEndEditing:(UISearchBar *)searchBar
{
NSLog(@"%s", __PRETTY_FUNCTION__);
}
回答1:
NSNull is just a singleton object used to represent null. It is traditionally used to wrap around nil values in containers(arrays and dictionaries) that cannot handle nil entries.
This error often comes up when parsing json and trying to add the result in a collection.
Are you doing something like this in your delegate method(s)?
Edit: Judging by the message you are sending to that NSNull (length), you probably get an "empty" result for a string you asked for and expected not be nil.
回答2:
After burning an entire day struggling with this, it came down to a totally unrelated problem: a corrupted storyboard.
This SO question recommended finding which scene was corrupt and recreating it. Unfortunately there was no way for me to determine that, so after some trial and error, it ended up being the initial view controller in my storyboard, which happened to be a UINavigationController. I deleted that, added it back in, and everything is golden.
来源：https://stackoverflow.com/questions/28304945/typing-in-uisearchbar-crashes-my-app