在CoreData上保存和检索UIImage

Question

在我的应用程序中,我正在尝试保存和检索核心数据中的图像.我可以在UIimage的约定成功后将图像成功保存到NSData中,但是当我试图将图像作为NSData时,它显示如下给出的输出,

案例1:尝试从DB显示为字符串时.

 <Event: 0x5b5d610> (entity: Event; id: 0x5b5ce30 <x-coredata://F51BBF1D-6484-4EB6-8583-147E23D9FF7B/Event/p1> ; data: <fault>)

案例2:尝试显示为数据时

 [Event length]: unrecognized selector sent to instance 0x5b3a9c0
 2010-07-28 19:11:59.610 IMG_REF[10787:207] *** Terminating app due to uncaught exception    'NSInvalidArgumentException', reason: '-[Event length]: unrecognized selector sent to instance 0x5b3a9c0'

我的代码,

to save:

NSManagedObjectContext *context = [self managedObjectContext];

newsObj = [NSEntityDescription insertNewObjectForEntityForName:@"Event" inManagedObjectContext:context];

NSURL *url = [NSURL URLWithString:@"http://www.cimgf.com/images/photo.PNG"];

NSData *data = [[NSData alloc] initWithContentsOfURL:url];

uiImage = [UIImage imageWithData:data];

NSData * imageData = UIImagePNGRepresentation(uiImage);

[newsObj setValue:imageData forKey:@"imgPng"];

NSError *error;

@try{

    if (managedObjectContext != nil) {

        if (![managedObjectContext save:&error]) {

            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);

            NSString * infoString = [NSString stringWithFormat:@"Please check your connection and try again."];

            UIAlertView * infoAlert = [[UIAlertView alloc] initWithTitle:@"Database Connection Error" message:infoString delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];

            [infoAlert show];

            [infoAlert release];
        } 
    }

}@catch (NSException *exception) {

    NSLog(@"inside exception");
}

检索,

    NSManagedObjectContext *context = [self managedObjectContext];

    NSFetchRequest * fetchRequest = [[NSFetchRequest alloc] init];

    NSEntityDescription *entity1 = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:context];

    [fetchRequest setEntity:entity1];

    NSError *error;

    NSArray * array = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];

    if (array == nil) {

        NSLog(@"Testing: No results found");

    }else {

        NSLog(@"Testing: %d Results found.", [array count]);
    }

    NSData * dataBytes = [[array objectAtIndex:0] data];

    image = [UIImage imageWithData:dataBytes];

    [fetchRequest release]; 


}

@catch (NSException *exception) {

    NSLog(@"inside exception");
}

Error:
   Testing: 3 Results found.
   2010-07-28 23:27:51.343 IMG_REF[11657:207] -[Event data]: unrecognized selector sent       to  instance 0x5e22ce0
   2010-07-28 23:27:51.344 IMG_REF[11657:207] *** Terminating app due to uncaught   exception 'NSInvalidArgumentException', reason: '-[Event data]: unrecognized selector sent  to instance 0x5e22ce0'
  *** Call stack at first throw:
  (
0   CoreFoundation                      0x02566919 __exceptionPreprocess + 185
1   libobjc.A.dylib                     0x026b45de objc_exception_throw + 47
2   CoreFoundation                      0x0256842b -[NSObject(NSObject) doesNotRecognizeSelector:] + 187
3   CoreFoundation                      0x024d8116 ___forwarding___ + 966
4   CoreFoundation                      0x024d7cd2 _CF_forwarding_prep_0 + 50
5   IMG_REF                             0x00003b06 -[IMG_REFViewController showAction] + 353
6   UIKit                               0x002bae14 -[UIApplication sendAction:to:from:forEvent:] + 119
7   UIKit                               0x004c214b -[UIBarButtonItem(UIInternal) _sendAction:withEvent:] + 156
8   UIKit                               0x002bae14 -[UIApplication sendAction:to:from:forEvent:] + 119
9   UIKit                               0x003446c8 -[UIControl sendAction:to:forEvent:] + 67
10  UIKit                               0x00346b4a -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 527
11  UIKit                               0x003456f7 -[UIControl touchesEnded:withEvent:] + 458
12  UIKit                               0x002de2ff -[UIWindow _sendTouchesForEvent:] + 567
13  UIKit                               0x002c01ec -[UIApplication sendEvent:] + 447
14  UIKit                               0x002c4ac4 _UIApplicationHandleEvent + 7495
15  GraphicsServices                    0x02dccafa PurpleEventCallback + 1578
16  CoreFoundation                      0x02547dc4 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 52
17  CoreFoundation                      0x024a8737 __CFRunLoopDoSource1 + 215
18  CoreFoundation                      0x024a59c3 __CFRunLoopRun + 979
19  CoreFoundation                      0x024a5280 CFRunLoopRunSpecific + 208
20  CoreFoundation                      0x024a51a1 CFRunLoopRunInMode + 97
21  GraphicsServices                    0x02dcb2c8 GSEventRunModal + 217
22  GraphicsServices                    0x02dcb38d GSEventRun + 115
23  UIKit                               0x002c8b58 UIApplicationMain + 1160
24  IMG_REF                             0x00002aac main + 102
25  IMG_REF                             0x00002a3d start + 53
 )
 terminate called after throwing an instance of 'NSException'

注意:执行NSData*dataBytes = [[array objectAtIndex:0] data]时会出现上面的错误; 线. 数据模型http://www.freeimagehosting.net/uploads/7c286931cc.png

我花了很多时间在这上面.请帮帮我!

Answer 1

不确定你是否已经理顺了这个,但我能够UIImage在Core Data中保存/检索对象,如下所示:

要保存:

NSData *imageData = UIImagePNGRepresentation(yourUIImage);
[newManagedObject setValue:imageData forKey:@"image"];

并加载:

NSManagedObject *selectedObject = [[self fetchedResultsController] objectAtIndexPath:indexPath];
UIImage *image = [UIImage imageWithData:[selectedObject valueForKey:@"image"]];
[[newCustomer yourImageView] setImage:image];

希望这可以帮助.我正在使用UITableView核心数据,并在我的tableView:didSelectRowAtIndexPath:方法中从数据库中提取图像.

Answer 2

这是适当的解决方案,非常有效.

1)使用核心数据存储UIImage:

NSData* coreDataImage = [NSData dataWithData:UIImagePNGRepresentation(delegate.dancePhoto)];

确保"coreDataImage"属于类型NSData.您必须在模型中为"coreDataImage"将类型设置为"二进制数据".

2)从核心数据中检索UIImage:

UIImage* image = [UIImage imageWithData:selectedDance.danceImage];

这就是它的全部,效果很好.

Answer 3

当您检索图像时,您正在执行获取请求并将结果存储在变量中array,这意味着array保存了一个事件对象的NSArray.然后,您稍后分配:

dataBytes = [array objectAtIndex:0];

这意味着dataBytes,您声明为NSData,现在实际上是Event的一个实例.然后当你去初始化图像时,部分执行imageWithData:调用length它期望成为你的NSData对象,但实际上是一个Event对象,因此是错误消息.

您应该将代码调整为:

dataBytes = [[array objectAtIndex:0] imgPng];

这样,你从数组中获取第一个Event对象,然后获取它的imgPng属性(NSData的一个实例,这就是你想要的).

作为旁注,您在上面dataBytes使用alloc- 的声明init可能是无关紧要的,因为您dataBytes之后立即更改为您的活动中的数据.

Answer 4

我使用的解决方案是创建下面的类别.您只需在项目中使用它即可.使用此存储图像就像存储NSData一样

的UIImage + NSCoding.h

@interface UIImage (UIImage_NSCoding) <NSCoding> 
- (void)encodeWithCoder:(NSCoder *)aCoder;
- (id)initWithCoder:(NSCoder *)aDecoder;
@end

的UIImage + NSCoding.m

#import "UIImage+NSCoding.h"

@implementation UIImage (UIImage_NSCoding)

- (void)encodeWithCoder:(NSCoder *)aCoder
{
    NSData *imageData = UIImagePNGRepresentation(self);
    [aCoder encodeDataObject:imageData];
}

- (id)initWithCoder:(NSCoder *)aDecoder
{
    [self autorelease];
    NSData* imageData = [aDecoder decodeDataObject];
    self = [[UIImage alloc] initWithData:imageData];
    return self;
}
@end