小胖说事35-----Terminating app due to uncaught exception 'CALayerInvalidGeometry', reason: 'CALayer posi

  1. 2011-06-11 15:19:17.167 ***[930:707] *** Terminating app due to uncaught exception 'CALayerInvalidGeometry', reason: 'CALayer position contains NaN: [160 nan]'  
  2. *** Call stack at first throw:  
  3. (  
  4.     0   CoreFoundation                      0x3365d64f __exceptionPreprocess + 114  
  5.     1   libobjc.A.dylib                     0x33aa0c5d objc_exception_throw + 24  
  6.     2   CoreFoundation                      0x3365d491 +[NSException raise:format:arguments:] + 68  
  7.     3   CoreFoundation                      0x3365d4cb +[NSException raise:format:] + 34  
  8.     4   QuartzCore                          0x361db61d _ZL18CALayerSetPositionP7CALayerRKN2CA4Vec2IdEEb + 140  
  9.     5   QuartzCore                          0x361db58b -[CALayer setPosition:] + 38  
  10.     6   QuartzCore                          0x361db4d7 -[CALayer setFrame:] + 390  
  11.     7   UIKit                               0x330eb455 -[UIView(Geometry) setFrame:] + 188  
  12.     8   UIKit                               0x3314854f -[UITableViewCell setFrame:] + 98  
  13.     9   UIKit                               0x33147b3b -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:withIndexPath:] + 850  
  14.     10  UIKit                               0x3314776b -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:] + 34  
  15.     11  UIKit                               0x331400cd -[UITableView(_UITableViewPrivate) _updateVisibleCellsNow:] + 936  
  16.     12  UIKit                               0x3313f27d -[UITableView layoutSubviews] + 140  
  17.     13  UIKit                               0x330eb5fb -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 26  
  18.     14  CoreFoundation                      0x335caf03 -[NSObject(NSObject) performSelector:withObject:] + 22  
  19.     15  QuartzCore                          0x361dcbb5 -[CALayer layoutSublayers] + 120  
  20.     16  QuartzCore                          0x361dc96d CALayerLayoutIfNeeded + 184  
  21.     17  QuartzCore                          0x361e21c5 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 212  
  22.     18  QuartzCore                          0x361e1fd7 _ZN2CA11Transaction6commitEv + 190  
  23.     19  QuartzCore                          0x361db055 _ZN2CA11Transaction17observer_callbackEP19__CFRunLoopObservermPv + 56  
  24.     20  CoreFoundation                      0x33634a35 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 16  
  25.     21  CoreFoundation                      0x33636465 __CFRunLoopDoObservers + 412  
  26.     22  CoreFoundation                      0x3363775b __CFRunLoopRun + 854  
  27.     23  CoreFoundation                      0x335c7ec3 CFRunLoopRunSpecific + 230  
  28.     24  CoreFoundation                      0x335c7dcb CFRunLoopRunInMode + 58  
  29.     25  GraphicsServices                    0x3413041f GSEventRunModal + 114  
  30.     26  GraphicsServices                    0x341304cb GSEventRun + 62  
  31.     27  UIKit                               0x33114d69 -[UIApplication _run] + 404  
  32.     28  UIKit                               0x33112807 UIApplicationMain + 670  
  33.     29  PXiPhone                            0x000028df main + 70  
  34.     30  PXiPhone                            0x00002894 start + 40  
  35. )  
  36. terminate called after throwing an instance of 'NSException  

    某天,加完一个功能,在iPhone4上报以上异常,然后crash掉,iPhone3上没事。百思不得其解,于是google之。看了一篇stackoverflow.com 的文章,说是某些地方代码除以0了,多见于自定义的UITableView自定义UITableViewCell高度的地方,如:tableView:heightForHeaderInSection:tableView:heightForFooterInSection:。这两个delegate方法都没有地方需要除的。在仔细看一下文章,说多见于适用sizeWithFont方法计算UILabel宽高的地方。恍然大悟,小弟有一个地方使用了UILabel来显示文本,需要用到sizeWithFont方法计算宽高的,在NSString为nil的时候,sizeWithFont会除以0了。

PS:在使用sizeWithFont计算UItabelView中label中字的长度时,由于表视图的cell是复用的,所以在计算label中的NSString的长度时,NSString可能为nil,此时可能会除以0,便会报错。

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