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

 1 2014-06-11 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  

今天,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。

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

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。