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

 

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

    某天，加完一個功能，在iPhone4上報以上異常，然后crash掉，iPhone3上沒事。百思不得其解，於是google之。看了一篇stackoverflow.com 的文章，說是某些地方代碼除以0了，多見於自定義的UITableView自定義UITableViewCell高度的地方，如：tableView:heightForHeaderInSection:或tableView:heightForFooterInSection:。這兩個delegate方法都沒有地方需要除的。在仔細看一下文章，說多見於適用sizeWithFont方法計算UILabel寬高的地方。恍然大悟，小弟有一個地方使用了UILabel來顯示文本，需要用到sizeWithFont方法計算寬高的，在NSString為nil的時候，sizeWithFont會除以0了。

原文：http://blog.csdn.net/hanspy/article/details/6538156

PS:在使用sizeWithFont計算UItabelView中label中字的長度時，由於表視圖的cell是復用的，所以在計算label中的NSString的長度時，NSString可能為nil，此時可能會除以0，便會報錯。