我的应用程序正在使崩溃声明索引21超出界限[0 .. 19]＆＃39; ***第一次抛出调用堆栈：

Question

我正在做一个聊天应用程序并从firebase中恢复数据。但在聊了一段时间之后就崩溃了。我无法找到问题在哪个阵列中。请帮助我找出哪个阵列。我正在使用Jsqmessageviewcontroller库。

NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 21 beyond bounds [0 .. 19]'
*** First throw call stack:
(
    0   CoreFoundation                      0x03bbc946 __exceptionPreprocess + 182
    1   libobjc.A.dylib                     0x02d33a97 objc_exception_throw + 44
    2   CoreFoundation                      0x03a92a93 -[__NSArrayM objectAtIndex:] + 243
    3   UIKit                               0x022f0a67 -[_UIFlowLayoutSection frameForItemAtIndexPath:] + 142
    4   UIKit                               0x022b5273 -[UICollectionViewFlowLayout _frameForItem:inSection:usingData:] + 123
    5   UIKit                               0x022b0e07 -[UICollectionViewFlowLayout layoutAttributesForItemAtIndexPath:usingData:] + 510
    6   UIKit                               0x022b1037 -[UICollectionViewFlowLayout layoutAttributesForItemAtIndexPath:] + 339
    7   ChatApp                             0x001af154 -[JSQMessagesCollectionViewFlowLayout layoutAttributesForItemAtIndexPath:] + 100
    8   ChatApp                             0x001b05ab -[JSQMessagesCollectionViewFlowLayout sizeForItemAtIndexPath:] + 123
    9   ChatApp                             0x001c53a2 -[JSQMessagesViewController scrollToBottomAnimated:] + 1266
    10  ChatApp                             0x000a2fe7 __37-[ChatpageViewController viewDidLoad]_block_invoke_3 + 103
    11  libdispatch.dylib                   0x045ff30a _dispatch_call_block_and_release + 15
    12  libdispatch.dylib                   0x0461fe2f _dispatch_client_callout + 14
    13  libdispatch.dylib                   0x0460690e _dispatch_main_queue_callback_4CF + 606
    14  CoreFoundation                      0x03b1695e __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 14
    15  CoreFoundation                      0x03ad5760 __CFRunLoopRun + 2256
    16  CoreFoundation                      0x03ad4bcb CFRunLoopRunSpecific + 443
    17  CoreFoundation                      0x03ad49fb CFRunLoopRunInMode + 123
    18  GraphicsServices                    0x04ed124f GSEventRunModal + 192
    19  GraphicsServices                    0x04ed108c GSEventRun + 104
    20  UIKit                               0x01b6a8b6 UIApplicationMain + 1526
    21  ChatApp                             0x000e020d main + 141
    22  libdyld.dylib                       0x0464bac9 start + 1
    23  ???                                 0x00000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

- (id<JSQMessageData>)collectionView:(JSQMessagesCollectionView *)collectionView messageDataForItemAtIndexPath:(NSIndexPath *)indexPath
{
    NSString * chat = [[DataArray objectAtIndex:indexPath.row] objectForKey:@"Message"];
    NSString * imageurl = [[DataArray objectAtIndex:indexPath.row] objectForKey:@"media"];
    NSString * vidimage = [[DataArray objectAtIndex:indexPath.row] objectForKey:@"imgurl"];

    if (chat == nil)
    {
        if ([imageurl rangeOfString:@".jpg"].location == NSNotFound)
        {
            NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
            NSString *documentsDirectory = [paths objectAtIndex:0];

            filepathurl = [NSURL URLWithString:imageurl];
            NSString *filewithext = [[filepathurl path] lastPathComponent];

            NSString *combined = [NSString stringWithFormat:@"%@/%@", documentsDirectory, filewithext];
            NSLog(@"=====>%@",combined);
            NSLog(@"Video is Loading....");
            [image1 sd_setImageWithURL:[NSURL URLWithString:vidimage]placeholderImage:nil];

            vitem = [[JSQPhotoMediaItem alloc] initWithImage:image1.image];

            // NSString * date12=[[DataArray objectAtIndex:indexPath.row] objectForKey:@"date"];
            if(![self.senderId isEqualToString:[[DataArray objectAtIndex:indexPath.row] objectForKey:@"UserId"]]){
                vitem .appliesMediaViewMaskAsOutgoing = NO;
            }

            NSString *dateString = [[DataArray objectAtIndex:indexPath.row] objectForKey:@"date"];
            NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];

            [dateFormatter setDateFormat:@"dd-MM-YY HH:mm a"];
            dateFromString = [[NSDate alloc] init];
            dateFromString=[dateFormatter dateFromString:dateString];

            messageForRow = [[JSQMessage alloc] initWithSenderId:[[DataArray objectAtIndex:indexPath.row] objectForKey:@"UserId"] senderDisplayName:[[DataArray objectAtIndex:indexPath.row] objectForKey:@"Name"]date:[[DataArray objectAtIndex:indexPath.row] objectForKey:@"date"]   media:vitem] ;

            //   JSQPhotoMediaItem *vitem = [[JSQPhotoMediaItem alloc] initWithImage:thumbnailImage];
        }
        else
        {
            image1 =[[UIImageView alloc]init];

            [image1 sd_setImageWithURL:[NSURL URLWithString:imageurl]
                      placeholderImage:nil];

            JSQPhotoMediaItem *item = [[JSQPhotoMediaItem alloc] initWithImage:image1.image];

            if(![self.senderId isEqualToString:[[DataArray objectAtIndex:indexPath.row] objectForKey:@"UserId"]]){
                item .appliesMediaViewMaskAsOutgoing = NO;
            }

            NSString *dateString = [[DataArray objectAtIndex:indexPath.row] objectForKey:@"date"];
            NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];

            [dateFormatter setDateFormat:@"dd-MM-YY HH:mm a"];
            //dateFromString = [[NSDate alloc] init];
            dateFromString=[dateFormatter dateFromString:dateString];

            messageForRow = [[JSQMessage alloc] initWithSenderId:[[DataArray objectAtIndex:indexPath.row] objectForKey:@"UserId"] senderDisplayName:[[DataArray objectAtIndex:indexPath.row] objectForKey:@"Name"] date:[[DataArray objectAtIndex:indexPath.row] objectForKey:@"date"] media:item] ;
        }
    }
    else
    {
        messageForRow = [[JSQMessage alloc] initWithSenderId:[[DataArray objectAtIndex:indexPath.row] objectForKey:@"UserId"] senderDisplayName:[[DataArray objectAtIndex:indexPath.row] objectForKey:@"Name"] date:[[DataArray objectAtIndex:indexPath.row] objectForKey:@"date"] text: [[DataArray objectAtIndex:indexPath.row] objectForKey:@"Message"]] ;
    }

    return messageForRow;
}