滾動時在UITableView上崩潰

Question

我正在開發一個小文本編輯器，我開始使用Table View模板，添加代碼以在其上列出app Documents目錄的內容，一切正常，我將一些文件復制到目錄，表視圖顯示它們，但是當我開始滾動時，它會崩潰。 我認為有些事情正在被釋放，而不是必須的。 這里我留下了代碼和崩潰日志:)

RootViewController.m

    NSFileManager *directoryContent;
- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    [self listDumpFiles];
}
// Customize the number of sections in the table view.
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return 1;
}


// Customize the number of rows in the table view.
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return [directoryContent count];
}


// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
    }

    // Configure the cell.
    cell.text = [directoryContent objectAtIndex:indexPath.row];
    return cell;
}
- (void)listDumpFiles {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];

    directoryContent = [[NSFileManager defaultManager] directoryContentsAtPath: documentsDirectory];

    NSLog(@"%@", documentsDirectory);
    return;
}

崩潰日志

2011-02-03 17:38:16.516 uNotes[15352:40b] /Users/pablo/Library/Application Support/iPhone Simulator/4.2/Applications/DF298F31-5723-4A1E-9EAA-3353C34BDCB2/Documents
2011-02-03 17:38:17.412 uNotes[15352:40b] -[NSCFString objectAtIndex:]: unrecognized selector sent to instance 0x9b243f0
2011-02-03 17:38:17.413 uNotes[15352:40b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSCFString objectAtIndex:]: unrecognized selector sent to instance 0x9b243f0'
*** Call stack at first throw:
(
    0   CoreFoundation                      0x00da7be9 __exceptionPreprocess + 185
    1   libobjc.A.dylib                     0x00efc5c2 objc_exception_throw + 47
    2   CoreFoundation                      0x00da96fb -[NSObject(NSObject) doesNotRecognizeSelector:] + 187
    3   CoreFoundation                      0x00d19366 ___forwarding___ + 966
    4   CoreFoundation                      0x00d18f22 _CF_forwarding_prep_0 + 50
    5   uNotes                              0x0000238c -[RootViewController tableView:cellForRowAtIndexPath:] + 216
    6   UIKit                               0x003247fa -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:withIndexPath:] + 634
    7   UIKit                               0x0031a77f -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:] + 75
    8   UIKit                               0x0032f450 -[UITableView(_UITableViewPrivate) _updateVisibleCellsNow:] + 1561
    9   UIKit                               0x00327538 -[UITableView layoutSubviews] + 242
    10  QuartzCore                          0x01c65451 -[CALayer layoutSublayers] + 181
    11  QuartzCore                          0x01c6517c CALayerLayoutIfNeeded + 220
    12  QuartzCore                          0x01c5e37c _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 310
    13  QuartzCore                          0x01c5e0d0 _ZN2CA11Transaction6commitEv + 292
    14  QuartzCore                          0x01c8e7d5 _ZN2CA11Transaction17observer_callbackEP19__CFRunLoopObservermPv + 99
    15  CoreFoundation                      0x00d88fbb __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 27
    16  CoreFoundation                      0x00d1e0e7 __CFRunLoopDoObservers + 295
    17  CoreFoundation                      0x00ce6bd7 __CFRunLoopRun + 1575
    18  CoreFoundation                      0x00ce6240 CFRunLoopRunSpecific + 208
    19  CoreFoundation                      0x00ce6161 CFRunLoopRunInMode + 97
    20  GraphicsServices                    0x016dc268 GSEventRunModal + 217
    21  GraphicsServices                    0x016dc32d GSEventRun + 115
    22  UIKit                               0x002bf42e UIApplicationMain + 1160
    23  uNotes                              0x00001fc0 main + 102
    24  uNotes                              0x00001f51 start + 53
)
terminate called after throwing an instance of 'NSException'
Program received signal:  “SIGABRT”.
(gdb) 

Answer 1

根據堆棧跟蹤，您嘗試在String上調用objectAtIndex: . 可能是內存管理問題。 啟用僵屍以獲取有關正在調用的對象的更多信息。

UPDATE

這可能就是這條線

directoryContent = [[NSFileManager defaultManager] directoryContentsAtPath: documentsDirectory];

我認為directoryContentsAtPath:返回一個自動釋放的對象。 如果在頭directoryContent中將directoryContent設置為@property(nonatomic, retain) ，則可以使用self.directoryContent = [[NSFileManager defaultManager] directoryContentsAtPath: documentsDirectory];設置它self.directoryContent = [[NSFileManager defaultManager] directoryContentsAtPath: documentsDirectory]; 並且它會自動保留NSFileManager返回的對象，否則可以調用directoryContent = [[[NSFileManager defaultManager] directoryContentsAtPath: documentsDirectory] retain]; 但是當你不再需要它時，一定要釋放它。