我是Core Data的新手，我遇到了一个问题。这个应用程序应该将照片库中的图像存储到核心数据，并在集合视图中显示它们。
然而，问题是在模拟器上新安装应用程序并且您只是添加图片时显示图片。但是，当您关闭应用程序并再次打开时，它会崩溃并在控制台中显示错误：线程1 EXC_BAD_ACCESS
// Loading Setup
@IBOutlet var collection: UICollectionView!
var images = [NSManagedObject]()
override func viewDidAppear(animated: Bool) {
let managedContext = AppDelegate().managedObjectContext
let fetchRequest = NSFetchRequest(entityName: "FullRes")
do {
let results =
try managedContext.executeFetchRequest(fetchRequest)
images = results as! [NSManagedObject]
} catch let error as NSError {
print("Could not fetch \(error), \(error.userInfo)")
}
collection.reloadData()
}
override func viewDidLoad() {
super.viewDidLoad()
imagePicker.delegate = self
// Uncomment the following line to preserve selection between presentations
// self.clearsSelectionOnViewWillAppear = false
// Register cell classes
self.collectionView!.registerClass(UICollectionViewCell.self, forCellWithReuseIdentifier: reuseIdentifier)
// Do any additional setup after loading the view.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
/*
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
// Get the new view controller using [segue destinationViewController].
// Pass the selected object to the new view controller.
}
*/
// MARK: UICollectionViewDataSource
override func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
// #warning Incomplete implementation, return the number of sections
return 1
}
override func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
// #warning Incomplete implementation, return the number of items
return images.count
}
override func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCellWithReuseIdentifier("cell", forIndexPath: indexPath) as! MainCollectionViewCell
let selectedObject = images[indexPath.row]
print(selectedObject)
let image: UIImage = UIImage(data: selectedObject.valueForKey("imageData") as! NSData!)!
cell.imageView.image = image
// Configure the cell
return cell
}
// MARK: UICollectionViewDelegate
/*
// Uncomment this method to specify if the specified item should be highlighted during tracking
override func collectionView(collectionView: UICollectionView, shouldHighlightItemAtIndexPath indexPath: NSIndexPath) -> Bool {
return true
}
*/
/*
// Uncomment this method to specify if the specified item should be selected
override func collectionView(collectionView: UICollectionView, shouldSelectItemAtIndexPath indexPath: NSIndexPath) -> Bool {
return true
}
*/
/*
// Uncomment these methods to specify if an action menu should be displayed for the specified item, and react to actions performed on the item
override func collectionView(collectionView: UICollectionView, shouldShowMenuForItemAtIndexPath indexPath: NSIndexPath) -> Bool {
return false
}
override func collectionView(collectionView: UICollectionView, canPerformAction action: Selector, forItemAtIndexPath indexPath: NSIndexPath, withSender sender: AnyObject?) -> Bool {
return false
}
override func collectionView(collectionView: UICollectionView, performAction action: Selector, forItemAtIndexPath indexPath: NSIndexPath, withSender sender: AnyObject?) {
}
*/
// Camera Setup
// the image picker
let imagePicker = UIImagePickerController()
// a queue to save the image without freezing the App UI
let saveQueue = dispatch_queue_create("saveQueue", DISPATCH_QUEUE_CONCURRENT)
// the Managed Object Context where we will save our image to.
let managedContext = AppDelegate().managedObjectContext
@IBAction func imageDidPress(sender: AnyObject) {
imagePicker.sourceType = UIImagePickerControllerSourceType.Camera
presentViewController(imagePicker, animated: true, completion: nil)
}
@IBAction func addDidPress(sender: AnyObject) {
imagePicker.sourceType = UIImagePickerControllerSourceType.PhotoLibrary
presentViewController(imagePicker, animated: true, completion: nil)
}
func imagePickerController(picker: UIImagePickerController, didFinishPickingImage image: UIImage, editingInfo: [String : AnyObject]?) {
prepareImageForSaving(image)
self.dismissViewControllerAnimated(true, completion: nil)
}
/*
func deletePhotoFromLibrary(info: [String : AnyObject]) {
print("wasrun")
let imageUrl = info[UIImagePickerControllerReferenceURL] as! NSURL
let imageUrls = [imageUrl]
//Delete asset
PHPhotoLibrary.sharedPhotoLibrary().performChanges( {
let imageAssetToDelete = PHAsset.fetchAssetsWithALAssetURLs(imageUrls, options: nil)
PHAssetChangeRequest.deleteAssets(imageAssetToDelete)
},
completionHandler: { success, error in
NSLog("Finished deleting asset. %@", (success ? "Success" : error!))
})
}
}
func imagePickerController(picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : AnyObject]) {
}
*/
func prepareImageForSaving(image:UIImage) {
// use date as unique id
let date : Double = NSDate().timeIntervalSince1970
// dispatch with gcd.
dispatch_async(saveQueue) {
// create NSData from UIImage
guard let imageData = UIImageJPEGRepresentation(image, 1) else {
// handle failed conversion
print("jpg error")
return
}
// scale image
let thumbnail = self.scale(image: image, toSize: self.view.frame.size)
guard let thumbnailData = UIImageJPEGRepresentation(thumbnail, 0.7) else {
// handle failed conversion
print("jpg error")
return
}
// send to save function
self.saveImage(imageData, thumbnailData: thumbnailData, date: date)
}
}
func saveImage(imageData:NSData, thumbnailData:NSData, date: Double) {
dispatch_barrier_async(saveQueue) {
// create new objects in moc
guard let fullRes = NSEntityDescription.insertNewObjectForEntityForName("FullRes", inManagedObjectContext: self.managedContext) as? FullRes, let thumbnail = NSEntityDescription.insertNewObjectForEntityForName("Thumbnail", inManagedObjectContext: self.managedContext) as? Thumbnail else {
// handle failed new object in moc
print("moc error")
return
}
//set image data of fullres
fullRes.imageData = imageData
//set image data of thumbnail
thumbnail.imageData = thumbnailData
thumbnail.id = date as NSNumber
//set relationship between the two objects
thumbnail.fullRes = fullRes
// save the new objects
do {
try self.managedContext.save()
} catch {
// implement error handling here
fatalError("Failure to save context: \(error)")
}
// clear the moc
self.managedContext.refreshAllObjects()
}
}
func scale(image image:UIImage, toSize newSize:CGSize) -> UIImage {
// make sure the new size has the correct aspect ratio
let aspectFill = resizeFill(image.size, toSize: newSize)
UIGraphicsBeginImageContextWithOptions(aspectFill, false, 0.0);
image.drawInRect(CGRectMake(0, 0, aspectFill.width, aspectFill.height))
let newImage:UIImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return newImage
}
func resizeFill(fromSize: CGSize, toSize: CGSize) -> CGSize {
let aspectOne = fromSize.height / fromSize.width
let aspectTwo = toSize.height / toSize.width
let scale : CGFloat
if aspectOne < aspectTwo {
scale = fromSize.height / toSize.height
} else {
scale = fromSize.width / toSize.width
}
let newHeight = fromSize.height / scale
let newWidth = fromSize.width / scale
return CGSize(width: newWidth, height: newHeight)
}
更新：根据下面的评论，我对代码进行了更改。
override func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCellWithReuseIdentifier("cell", forIndexPath: indexPath) as! MainCollectionViewCell
if let imagePath = images[indexPath.row].imageData {
cell.imageView.image = UIImage(data: imagePath)
}
// Configure the cell
return cell
}
但现在，我收到另一个错误：2015-12-26 20：10：24.464收集[480：69113] - [缩略图imageData]：无法识别的选择器发送到实例0x13fe9ba00。
AppDelegate.swift上的代码class AppDelegate: UIResponder, UIApplicationDelegate {突出显示。
这个应用有效，直到某一点。例如，当我从手机上卸载应用程序时，我正在运行它然后再次重新运行它，它会工作一段时间直到它崩溃。
但是，它仍然不像我希望的那样完美。有时，只有添加了另一张图片才会出现一张图片。
更新2：我根据您的评论进行了一些调整：
override func viewDidAppear(animated: Bool) {
authenticateUser()
let managedContext = AppDelegate().managedObjectContext
let fetchRequest = NSFetchRequest(entityName: "Thumbnail")
managedContext.performBlockAndWait { () -> Void in
do {
let results =
try managedContext.executeFetchRequest(fetchRequest)
self.images = results as! [Thumbnail]
} catch let error as NSError {
print("Could not fetch \(error), \(error.userInfo)")
}
}
collection.reloadData()
}
每当我删除应用程序并重新运行它时，它都能正常工作。但是，当应用关闭时，它将无法再恢复图像。
我在运行时仍然会-[Thumbnail imageData]: unrecognized selector sent to instance 0x13762d650。 AppDelegate.swift
class AppDelegate: UIResponder, UIApplicationDelegate {
答案 0 :(得分：0)
你是对的，我对另一个问题的答案有误。
CoreData需要在一个NSManagedObjectContext中的所有操作发生在与创建它的同一个线程上。我更新了答案。
以下是相关代码：
在UIViewController
let convertQueue = dispatch_queue_create("convertQueue", DISPATCH_QUEUE_CONCURRENT) // this one is for image stuff
let saveQueue = dispatch_queue_create("saveQueue", DISPATCH_QUEUE_CONCURRENT) // this one is for CoreData
在正确的线程上设置moc的值
extension ViewController {
// call this in viewDidLoad
func coreDataSetup() {
dispatch_sync(saveQueue) {
self.managedContext = AppDelegate().managedObjectContext
}
}
}
使用以下方式保存图像
extension ViewController {
func saveImage(imageData:NSData, thumbnailData:NSData, date: Double) {
dispatch_barrier_sync(saveQueue) {
// create new objects in moc
guard let moc = self.managedContext else {
return
}
guard let fullRes = NSEntityDescription.insertNewObjectForEntityForName("FullRes", inManagedObjectContext: moc) as? FullRes, let thumbnail = NSEntityDescription.insertNewObjectForEntityForName("Thumbnail", inManagedObjectContext: moc) as? Thumbnail else {
// handle failed new object in moc
print("moc error")
return
}
//set image data of fullres
fullRes.imageData = imageData
//set image data of thumbnail
thumbnail.imageData = thumbnailData
thumbnail.id = date as NSNumber
thumbnail.fullRes = fullRes
// save the new objects
do {
try moc.save()
} catch {
fatalError("Failure to save context: \(error)")
}
// clear the moc
moc.refreshAllObjects()
}
}
}