由於內存壓力而終止

Question

我有一個收集視圖，該視圖從文檔目錄加載圖像。 當我嘗試將這些圖像加載到collectionview時，應用程序崩潰並顯示內存警告。

-(UICollectionViewCell*)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
UIImage *cellImage;
if (indexPath.section == 0) {

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectoryPath = [paths objectAtIndex:0];
    NSString *folderPath = [documentsDirectoryPath  stringByAppendingPathComponent:@"Photos"];  // subDirectory
    NSString *filePath;    
    if ([[NSFileManager defaultManager] fileExistsAtPath:folderPath])
        filePath = [folderPath stringByAppendingPathComponent:[NSString stringWithFormat:@"Photo%d",indexpath.row]];

    cellImage = [UIImage imageWithContentsOfFile:filePath];

} else if (indexPath.section == 1){
    cellImage = [UIImage imageNamed:@"btn_vid.png"];
} else if (indexPath.section == 2){
    cellImage = [UIImage imageNamed:@"btn_mic.png"];
} else if (indexPath.section == 3){
    cellImage = [UIImage imageNamed:@"btn_1.png"];
}
UIImageView *imageView = (UIImageView *)[cell viewWithTag:100];
[imageView setImage:cellImage];

return cell;
}

我究竟做錯了什么？

更新：

圖像尺寸合適，因為我是從手機的攝像頭上取下來並保存在文檔目錄中的

更新：

我已經收到有關為圖像添加縮略圖的建議，然后從Airsource Ltd.加載它們。 我使用此代碼生成了縮略圖圖像，而不是他的圖像，它起作用了。 但我想知道哪個更好。

+(UIImage*) generateThumbnailFromImage:(UIImage*)theImage
{
UIImage * thumbnail;
CGSize destinationSize = CGSizeMake(80,80);

UIGraphicsBeginImageContext(destinationSize);
[theImage drawInRect:CGRectMake(0,0,destinationSize.width, destinationSize.height)];
thumbnail = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

return thumbnail;
}

Answer 1

您正在加載完整尺寸的圖像，但是大概只顯示了一個縮略圖。 但是，就目前情況而言，UIImage需要將完整的，解壓縮的圖像保留在內存中，以顯示按比例縮小的版本，這效率很低。

要生成縮略圖，請將文件作為NSData加載，然后使用標准的Apple代碼生成縮略圖。 不要並行執行太多操作，否則您將遇到完全相同的問題

CGImageRef MyCreateThumbnailImageFromData (NSData * data, int imageSize)
{
    CGImageRef        myThumbnailImage = NULL;
    CGImageSourceRef  myImageSource;
    CFDictionaryRef   myOptions = NULL;
    CFStringRef       myKeys[3];
    CFTypeRef         myValues[3];
    CFNumberRef       thumbnailSize;

   // Create an image source from NSData; no options.
   myImageSource = CGImageSourceCreateWithData((CFDataRef)data,
                                               NULL);
   // Make sure the image source exists before continuing.
   if (myImageSource == NULL){
        fprintf(stderr, "Image source is NULL.");
        return  NULL;
   }

   // Package the integer as a  CFNumber object. Using CFTypes allows you
   // to more easily create the options dictionary later.
   thumbnailSize = CFNumberCreate(NULL, kCFNumberIntType, &imageSize);

   // Set up the thumbnail options.
   myKeys[0] = kCGImageSourceCreateThumbnailWithTransform;
   myValues[0] = (CFTypeRef)kCFBooleanTrue;
   myKeys[1] = kCGImageSourceCreateThumbnailFromImageIfAbsent;
   myValues[1] = (CFTypeRef)kCFBooleanTrue;
   myKeys[2] = kCGImageSourceThumbnailMaxPixelSize;
   myValues[2] = (CFTypeRef)thumbnailSize;

   myOptions = CFDictionaryCreate(NULL, (const void **) myKeys,
                   (const void **) myValues, 2,
                   &kCFTypeDictionaryKeyCallBacks,
                   & kCFTypeDictionaryValueCallBacks);

  // Create the thumbnail image using the specified options.
  myThumbnailImage = CGImageSourceCreateThumbnailAtIndex(myImageSource,
                                          0,
                                          myOptions);
  // Release the options dictionary and the image source
  // when you no longer need them.
  CFRelease(thumbnailSize);
  CFRelease(myOptions);
  CFRelease(myImageSource);

   // Make sure the thumbnail image exists before continuing.
   if (myThumbnailImage == NULL){
         fprintf(stderr, "Thumbnail image not created from image source.");
         return NULL;
   }

   return myThumbnailImage;
}