無法更快地將本地存儲的圖像加載到集合視圖中。

Question

我有多個圖像和視頻存儲在應用程序文檔目錄中。我以這種方式使用SDWebImage在集合視圖中顯示該圖像和視頻。

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{ 


AlbumImageCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"AlbumImageCell" forIndexPath:indexPath]; 
cell.albumImage.image=nil; 
cell.layer.shouldRasterize = YES; 
cell.layer.rasterizationScale = [UIScreen mainScreen].scale; 
if (cell == nil) { 
    cell = [[[NSBundle mainBundle] loadNibNamed:@"AlbumImageCell" owner:self options:nil] objectAtIndex:0]; 
} 

NSInteger Type=[[[self.arrTbl_Album_Image objectAtIndex:indexPath.row] objectAtIndex:3] intValue]; 
if (Type==1) { 
     cell.imgPlay.hidden=YES; 
     [cell.albumImage setImage:[images objectAtIndex:indexPath.row]]; 
    }else{ 
     cell.imgPlay.hidden=NO; 
     [cell.albumImage setImage:[images objectAtIndex:indexPath.row]]; 
    } 

    return cell; 
} 

這裏是生成縮略圖的代碼。

-(void)load_Album_Data{ 
     NSUserDefaults *album_id=[NSUserDefaults standardUserDefaults]; 
     NSInteger Album_id=[album_id integerForKey:@"album_Id"]; 

//From the query. 
NSString *query=[NSString stringWithFormat:@"select * from tbl_Album_Image where album_id='%ld' order by id desc",Album_id]; 


//Get result. 
if (self.arrTbl_Album_Image != nil) { 
    self.arrTbl_Album_Image=nil; 
} 
self.arrTbl_Album_Image=[[NSArray alloc]initWithArray:[self.dbManager loadDataFromDB:query]]; 


dispatch_queue_t myQueue = dispatch_queue_create("MyQueue",NULL); 
dispatch_async(myQueue, ^{ 

for(int i=0;i<self.arrTbl_Album_Image.count;i++) 
{ 
    NSInteger AssetType=[[[self.arrTbl_Album_Image objectAtIndex:i] objectAtIndex:3] intValue]; 
    if (AssetType==1) { 
     //for image 
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 

    NSString *documentsDirectory = [paths objectAtIndex:0]; 
    NSString *inputPath = [[self.arrTbl_Album_Image objectAtIndex:i]objectAtIndex:2 ]; 

    NSString *imageEx=[inputPath pathExtension]; 
    NSString *imageName=[[inputPath lastPathComponent]stringByDeletingPathExtension]; 

    NSString *fullPath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@",imageName,imageEx]]; 

    UIImage *img=[UIImage imageWithContentsOfFile:fullPath]; 
    CGFloat scale = MAX(106/img.size.width, 106/img.size.height); 
    CGFloat width = img.size.width * scale; 
    CGFloat height = img.size.height * scale; 
    CGRect imageRect = CGRectMake((106 - width)/2.0f, 
            (106 - height)/2.0f, 
            width, 
            height); 
    CGSize c=CGSizeMake(106, 106); 
    UIGraphicsBeginImageContextWithOptions(c, NO, 0); 
    [img drawInRect:imageRect]; 
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext(); 
    UIGraphicsEndImageContext(); 


    [images addObject:newImage]; 
    } 
    else{ 
     //for video 
     NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 

     NSString *documentsDirectory = [paths objectAtIndex:0]; 
     NSString *inputPath = [[self.arrTbl_Album_Image objectAtIndex:i]objectAtIndex:2 ]; 

     NSString *imageEx=[inputPath pathExtension]; 
     NSString *imageName=[[inputPath lastPathComponent]stringByDeletingPathExtension]; 

     NSString *fullPath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@",imageName,imageEx]]; 

     NSURL *videoURL = [NSURL fileURLWithPath:fullPath]; 
     AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:videoURL options:nil]; 

     AVAssetImageGenerator *imageGenerator = [[AVAssetImageGenerator alloc] initWithAsset:asset]; 
     imageGenerator.appliesPreferredTrackTransform = YES; 
     NSError *err = NULL; 
     CMTime time = CMTimeMake(1, 2); 
     CGImageRef imageRef = [imageGenerator copyCGImageAtTime:time actualTime:NULL error:&err]; 
     UIImage *thumbNailImage = [[UIImage alloc] initWithCGImage:imageRef]; 


     CGFloat scale = MAX(106/thumbNailImage.size.width, 106/thumbNailImage.size.height); 
     CGFloat width = thumbNailImage.size.width * scale; 
     CGFloat height = thumbNailImage.size.height * scale; 
     CGRect imageRect = CGRectMake((106 - width)/2.0f, 
             (106 - height)/2.0f, 
             width, 
             height); 
     CGSize c=CGSizeMake(106, 106); 
     UIGraphicsBeginImageContextWithOptions(c, NO, 0); 
     [thumbNailImage drawInRect:imageRect]; 
     UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext(); 
     UIGraphicsEndImageContext(); 

      [images addObject:newImage]; 

    } 

    dispatch_async(dispatch_get_main_queue(), ^{ 
      //Reload the Image view. 
    [self.album_ImageView reloadData]; 
        } 


    }); 

} 
}); 


} 

但問題是我無法更快地加載圖像，並且當上下滾動發生得很快時，應用程序崩潰。並且還不生成視頻圖像。 請幫我解決這個問題，併爲我提供任何解決方案。 我想在集合視圖單元格中加載快速圖像。

Answer 1

，而不是我們的代碼來設置圖像的變化來此

[cell.albumImage sd_setImageWithURL:imaURL placeholderImage:[UIImage imageNamed:@"placeholder.png"] options:SDWebImageRefreshCached completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) { 

     dispatch_async(dispatch_get_main_queue(), ^{ 

      cell.albumImage.image=image; 
     }); 
    }]; 

它將加載速度更快，甚至保存在高速緩存

Answer 2

看來，當你從照片庫中保存圖像，您應該保存等等如果你需要它的全尺寸，並保存適當的縮放版本的圖像，你可以用它來顯示在應用程序中。如果使用的ALAsset可能是thumbnail。

如果你這樣做，圖像加載將會很快並且內存使用量最小。

目前，您只是試圖將過多的圖像數據加載到內存中，而且這會花費很長時間並在應用程序不可避免地耗盡時崩潰。使用設備攝像頭拍攝的圖像實際上非常大...