在 CoreData 上保存和检索 UIImage

Question

在我的应用程序中，我尝试在核心数据中保存和检索图像。在将 UIimage 转换为 NSData 后，我能够成功保存图像，但是当我尝试将图像获取为 NSData 时，它会显示如下输出，

情况 1：当尝试从数据库显示为字符串时。

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

情况2：当尝试显示为数据

 [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'

我的代码时，

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");
}

要检索，

    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]; 时会出现上述错误线。 数据模型 http://www.freeimagehosting.net/uploads/7c286931cc.png

我花了很多时间这。请帮帮我！

Answer 1

不确定您是否已经解决了这个问题，但我可以在核心数据中保存/检索 UIImage 对象，如下所示：

保存：

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

和加载：

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

希望这会有所帮助。我正在将 UITableView 与 Core Data 结合使用，并在 tableView:didSelectRowAtIndexPath: 方法中从数据库中提取图像。

Answer 2

这是有效的正确解决方案。

1) 使用核心数据存储 UIImage：

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

确保“coreDataImage”的类型为 NSData。您必须将模型中“coreDataImage”的类型设置为“二进制数据”。

2) 从核心数据中检索 UIImage：

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

这就是全部内容，效果很好。

Answer 3

当您检索图像时，您将执行获取请求并将结果存储在变量 array 中，这意味着 array 保存 Event 对象的 NSArray。然后，稍后，您分配：

dataBytes = [array objectAtIndex:0];

这意味着您声明为 NSData 的 dataBytes 现在实际上是 Event 的实例。然后，当您初始化图像时，imageWithData: 的部分实现会调用 length ，它期望成为您的 NSData 对象，但实际上是一个 Event 对象，因此错误消息。

您应该将代码调整为：

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

这样，您将从数组中获取第一个 Event 对象，然后获取其 imgPng 属性（NSData 的实例，这就是您想要的）。

附带说明一下，您在上面一行中使用 alloc-init 声明 dataBytes 可能是无关的，因为您更改了 dataBytes 是紧接着您的事件的数据。

Answer 4

我使用的解决方案是创建以下类别。您只需要在项目中使用它即可正常工作。 一样

使用此存储图像的方式就像存储 NSData UIImage+NSCoding.h

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

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

Answer 5

此示例代码示例了如何在 Core Data 中存储 UIImage：
https://developer.apple.com/library/ios/ #samplecode/PhotoLocations/Introduction/Intro.html