Terminating app due to uncaught exception 'CALayerInvalidGeometry', reason: 'CALayer position contains NaN: [160 nan]解决方法

2011-06-11 15:19:17.167 ***[930:707] *** Terminating app due to uncaught exception 'CALayerInvalidGeometry', reason: 'CALayer position contains NaN: [160 nan]'*** Call stack at first throw:(0 CoreFoundation 0x3365d64f __exceptionPreprocess + 1141 libobjc.A.dylib 0x33aa0c5d objc_exception_throw + 242 CoreFoundation 0x3365d491 +[NSException raise:format:arguments:] + 683 CoreFoundation 0x3365d4cb +[NSException raise:format:] + 344 QuartzCore 0x361db61d _ZL18CALayerSetPositionP7CALayerRKN2CA4Vec2IdEEb + 1405 QuartzCore 0x361db58b -[CALayer setPosition:] + 386 QuartzCore 0x361db4d7 -[CALayer setFrame:] + 3907 UIKit 0x330eb455 -[UIView(Geometry) setFrame:] + 1888 UIKit 0x3314854f -[UITableViewCell setFrame:] + 989 UIKit 0x33147b3b -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:withIndexPath:] + 85010 UIKit 0x3314776b -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:] + 3411 UIKit 0x331400cd -[UITableView(_UITableViewPrivate) _updateVisibleCellsNow:] + 93612 UIKit 0x3313f27d -[UITableView layoutSubviews] + 14013 UIKit 0x330eb5fb -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 2614 CoreFoundation 0x335caf03 -[NSObject(NSObject) performSelector:withObject:] + 2215 QuartzCore 0x361dcbb5 -[CALayer layoutSublayers] + 12016 QuartzCore 0x361dc96d CALayerLayoutIfNeeded + 18417 QuartzCore 0x361e21c5 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 21218 QuartzCore 0x361e1fd7 _ZN2CA11Transaction6commitEv + 19019 QuartzCore 0x361db055 _ZN2CA11Transaction17observer_callbackEP19__CFRunLoopObservermPv + 5620 CoreFoundation 0x33634a35 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 1621 CoreFoundation 0x33636465 __CFRunLoopDoObservers + 41222 CoreFoundation 0x3363775b __CFRunLoopRun + 85423 CoreFoundation 0x335c7ec3 CFRunLoopRunSpecific + 23024 CoreFoundation 0x335c7dcb CFRunLoopRunInMode + 5825 GraphicsServices 0x3413041f GSEventRunModal + 11426 GraphicsServices 0x341304cb GSEventRun + 6227 UIKit 0x33114d69 -[UIApplication _run] + 40428 UIKit 0x33112807 UIApplicationMain + 67029 PXiPhone 0x000028df main + 7030 PXiPhone 0x00002894 start + 40)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:或tableView:heightForFooterInSection:。

    小弟愚笨，还是想不通，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会除以了。

    哈，解决之，内牛满面。