ios - 从核心数据中获取 UIImage

Question

我正在使用 Core Data 来保存从 UIImagePickerController(源类型 = 图像库)中获取的 UIImage。然后我将照片放在或更确切地说是想将照片放在 UICollectionViewCell 中，请帮助并检查我做错了什么。

这是我的 UIImagePickerController，它由委托(delegate)调用。

-(void)requestAddScreen {
_picker = [[UIImagePickerController alloc] init];
_picker.delegate = self;
_picker.allowsEditing = NO;
_picker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
[self presentViewController:_picker animated:YES completion:nil];
}

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage:(UIImage *)image editingInfo:(NSDictionary *)editingInfo
{

AppDelegate *delegate = [UIApplication sharedApplication].delegate;
NSManagedObjectContext *context = [delegate managedObjectContext];
NSEntityDescription* entityDescription = [NSEntityDescription entityForName:@"Screen" inManagedObjectContext:context];

Screen* newScreen = [[Screen alloc] initWithEntity:entityDescription insertIntoManagedObjectContext:context];
NSData *imageData = UIImagePNGRepresentation(image);
newScreen.image = imageData;
[_project addProjectScreensObject:newScreen];

NSError *error;
[context save:&error];



if (![context save:&error]) {
    NSLog(@"Whoops %@ %@", error, [error localizedDescription]);
}


[self dismissViewControllerAnimated:_picker completion:^{
[_collectionView reloadData];
}];  
}

这是我遇到的 ViewWillAppear。这是我从 Core Data 获取数据的地方，是否正确？

- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:nil];
AppDelegate *delegate = [UIApplication sharedApplication].delegate;
NSManagedObjectContext *context = [delegate managedObjectContext];

//load project
NSFetchRequest *fetch = [[NSFetchRequest alloc]init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Project" inManagedObjectContext:context];
[fetch setEntity:entity];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name == %@", @"EMO-KIT"];
[fetch setPredicate:predicate];
NSError *error;
NSArray *array = [context executeFetchRequest:fetch error:&error];
if (array.count == 1) {
    _project = array[0];
} else {
    _project = [NSEntityDescription insertNewObjectForEntityForName:@"Project" inManagedObjectContext:context];
    [_project   setValue:@"EMO-KIT" forKey:@"name"];
}
NSArray* screens = [[_project projectScreens] array];
NSIndexPath *bottomIndexPath=[NSIndexPath indexPathForRow:screens.count inSection:0];
[self.collectionView scrollToItemAtIndexPath: bottomIndexPath atScrollPosition:UICollectionViewScrollPositionRight animated:YES];

}

Answer 1

您可以将 UIImage 转换为 NSData 并保存到 Core Data 中，如下所示

保存

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

检索

UIImage *image = [UIImage imageWithData:[screenObj valueForKey:@"Image"]];

希望对你有帮助