ios - UIImage(contentsOfFile) 的内存问题

Question

我有一个 Collection View ，可以从文档目录加载一些图像:

func reloadNotesFromStore() {
    {

        let fetchRequest = NSFetchRequest(entityName: "TaskDraw")

        let formsPredicate = NSPredicate(format: "task_id = %@", self.task_id)
        fetchRequest.predicate = formsPredicate

        let sortDescriptor = NSSortDescriptor(key: "createdAt", ascending: false)
        let sortDescriptors = [sortDescriptor]
        fetchRequest.sortDescriptors = sortDescriptors

        self.photos.removeAll(keepCapacity: false)

        let taskDrawings = (try! context.executeFetchRequest(fetchRequest)) as! [TaskDraw]

        let path = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)[0] as NSURL

        for taskDraw in taskDrawings {

            let imageFilename = "\(taskDraw.remoteID!)_combined.png"
            let imageFullPath = path.URLByAppendingPathComponent("\(self.task_id)/\(imageFilename)")

            // create combined image to display
            let photo = Photo(image: UIImage(contentsOfFile: imageFullPath.path!)!)

            photo.selected = false
            photo.taskDraw = taskDraw

            self.photos.append(photo)
        }

        } ~> {
            self.collectionView?.reloadData()
    }

}

每次当我显示我的 CollectionViewController 时，我的内存使用量都会增加大约 30 MB。

我使用 UIImage(contentsOfFile) 加载的图像约为 150 kb。

好吧，没有尝试 Leos 解决方案，但仍然没有成功。当我重新加载我的 Controller (模态)时，我的内存总是增加约 30-40 MB。

func reloadNotesFromStore() {
    {

        let fetchRequest = NSFetchRequest(entityName: "TaskDraw")

        let formsPredicate = NSPredicate(format: "task_id = %@", self.task_id)
        fetchRequest.predicate = formsPredicate

        let sortDescriptor = NSSortDescriptor(key: "createdAt", ascending: false)
        let sortDescriptors = [sortDescriptor]
        fetchRequest.sortDescriptors = sortDescriptors

        self.items.removeAll(keepCapacity: false)

        let taskDrawings = (try! context.executeFetchRequest(fetchRequest)) as! [TaskDraw]

        let path = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)[0] as NSURL

        for taskDraw in taskDrawings {

            let imageFilename = "\(taskDraw.remoteID!)_combined.png"
            let imageFullPath = path.URLByAppendingPathComponent("\(self.task_id)/\(imageFilename)")

            // create combined image to display
            let collectionViewItem = CollectionViewItem()
            collectionViewItem.filePath = imageFullPath
            collectionViewItem.selected = false
            collectionViewItem.taskDraw = taskDraw

            self.items.append(collectionViewItem)
        }

        } ~> {
            self.collectionView?.reloadData()
    }

}

override func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {

    let cell = collectionView.dequeueReusableCellWithReuseIdentifier("PhotoCell", forIndexPath: indexPath) as! PhotoCell

    let item = items[indexPath.item]

    cell.imageView.image = UIImage(contentsOfFile: item.filePath!.path!)!
    .....

我如何强制 Swift 释放我的内存？更新2:

当我使用 UIImage(named: ..) 而不是 UIImage(contentsOfFile: ....) 时，第一次初始化时内存会增加约 40 MB，但当我关闭 View 并再次加载时，内存会保持不变(我猜发生这种情况是因为命名:..缓存图像)

但这也不会在错误关闭 VC 时释放内存。

Answer 1

好的，我现在使用以下解决方案解决了问题:

我仍然在内存中创建一个 UIImage，如下所示:

for taskDraw in taskDrawings {

       let imageFilename = "\(taskDraw.remoteID!)_combined.png"
       let imageFullPath = path.URLByAppendingPathComponent("\(self.task_id)/\(imageFilename)")

       let photo = Photo(image: UIImage(contentsOfFile: imageFullPath.path!)!.resizeToWidth(300))
       photo.taskDraw = taskDraw
       photo.addNote = false
       self.photos.append(photo)

因此仅在 CollectionView 中显示调整大小的图像。 (否则我需要在磁盘上存储缩略图)

还有:

override func viewWillDisappear(animated: Bool) {
    super.viewWillDisappear(animated)
    self.photos.removeAll(keepCapacity: false)
}

在 Controller 中。

现在，内存消耗相当低，并且在关闭我的 ViewController 后，已使用的内存现在被释放。