由于内存压力而终止

debugcn 发表于 Dev

阿宾·乔治（Abin George）

我有一个收集视图，该视图从文档目录加载图像。当我尝试将这些图像加载到collectionview时，应用程序崩溃并显示内存警告。

-(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;
}

我究竟做错了什么？

更新：在此处输入图片说明

图像尺寸合适，因为我是从手机的摄像头上取下来并保存在文档目录中的

更新：

我已经收到有关为图像添加缩略图的建议，然后从Airsource Ltd.加载它们。我使用此代码生成了缩略图图像，而不是他的图像，它起作用了。但是我想知道，哪个更好。

+(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;
}

空气资源有限公司

您正在加载完整尺寸的图像，但是大概只显示了一个缩略图。但是，就目前情况而言，UIImage需要将完整的，解压缩的图像保留在内存中，以便显示按比例缩小的版本，这效率很低。

要生成缩略图，请以NSData格式加载文件，然后使用标准的Apple代码生成缩略图。不要并行执行太多操作，否则您将遇到完全相同的问题

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;
}

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