下载大量图像时发生内存泄漏问题

Question

我试图在屏幕顶部向用户下载多于600张图像，并在屏幕上方显示进度表。我使用淡入淡出层来屏蔽我的屏幕，以显示活动和进度。

我收到之间的内存警告消息和应用程序崩溃。

我的步骤，以达到循环是：

1. 在应用程序委托，我检查第一核心数据表针对其具有isImageAvailable布尔字段“0”值的所有行。
2. 如果显示我一些计数（比如说600），并且我用YES和NO选项显示并提醒。
3. 在是：[self performSelector：@selector（myDownload :) withObject：nil afterDelay：0.2];

4. 在myDownload

   NSOperationQueue *queue = [NSOperationQueue new]; 
   // Create our NSInvocationOperation to call loadDataWithOperation, passing in nil 
   NSInvocationOperation *operation = [[NSInvocationOperation alloc] initWithTarget:self 
                      selector:@selector(startUpdatingRecords:) object:nil]; 
   
   // Add the operation to the queue 
   [queue addOperation:operation]; 
   [operation release]; 
   [queue release]; 
   

5. 在startUpdatingRecords：

   -(void)startUpdatingRecords:(id)sender 
   {  
   [self performSelectorInBackground:@selector(updateProgressMeter:) withObject: [NSString stringWithFormat:@"%d",self.loopStartIndex]]; 
   
   // Variable declarations    
   CGSize newSizeLarge ; 
   NSPredicate *predicate; 
   NSMutableArray *MatchingID; 
   Image_DB *data; 
   
   // Cache Directory path 
   NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES); 
   
   NSData *responseData; // = [[NSData alloc]init] ; 
   
   NSURL *url = [[[NSURL alloc]init] autorelease]; 
   NSMutableURLRequest *request = [[[NSMutableURLRequest alloc]init] autorelease]; 
   UIImage *imgSelected_Large = [[[UIImage alloc]init] autorelease]; 
   
   // Loop through all IDs 
   for (int i = 0; i < [self.arrayOfID count]; i++) //for (int i = loopStart; i < loopEnd; i++) 
   { 
   if (self.abortDownload) 
   {   
       break; 
   } 
   
   NSString *documentsDirectory = [[[NSString alloc] initWithFormat:@"%@",[paths objectAtIndex:0]] autorelease]; 
   documentsDirectory = [paths objectAtIndex:0]; 
   documentsDirectory = [documentsDirectory stringByAppendingFormat:@"/ImageFolder"]; // Image folder path 
   
   myClass *classObj = [self.arrayOfID objectAtIndex:i]; 
   
   NSString *strURl = [[[NSString alloc] initWithFormat:@"%@%@", self.MyURL,recipeObj.recipeImageStr] autorelease]; 
   //NSLog(@"URL = %@",strURl);   
   
   url = [NSURL URLWithString:strURl]; 
   request = [NSMutableURLRequest requestWithURL:url]; 
   responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:NULL error:NULL]; // Get Image Data into NSData 
   
   //imgSelected_Large = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:strURl]]]; 
   
   NSLog(@"Download Count = %d",i+1); 
   
   if (responseData != nil) 
   { 
       imgSelected_Large = [UIImage imageWithData:responseData]; 
   
       // Resizining image 
       newSizeLarge.width = 320;  
       newSizeLarge.height = 180;  
   
       imgSelected_Large = [self imageWithImage:imgSelected_Large scaledToSize:newSizeLarge]; // New sized image 
       NSData *dataPhoto; // no need to release it because UIImageJPEGRepresentation gives autoreleased NSData obj. 
       dataPhoto = UIImageJPEGRepresentation(imgSelected_Large, 0.6); // Set new image representation and its Compression Quality 
   
       documentsDirectory = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"Image_%d", classObj.nodeID]];    
       [dataPhoto writeToFile:documentsDirectory atomically:YES]; //Write file to local folder at default path 
   
       predicate = [NSPredicate predicateWithFormat: @"(image_ID = %d)",recipeObj.nodeID]; 
       MatchingID = [CoreDataAPIMethods searchObjectsInContext:@"Image_DB" :predicate :@"image_ID" :YES :self.managedObjectContext]; 
   
       // Setting flag variable for available image 
       for (int j = 0; j< [MatchingID count]; j++) 
       { 
        //Assign the Authors Records in Class Object and save to Database 
        data = (Image_DB*) [MatchingID objectAtIndex:j];     
        // data.image_large = dataPhoto; // Code for storing BLOB object to DB 
        data.extra_1 = @"1"; 
        //NSLog(@"Flag updated"); 
       } 
   } 
   // Exit out code 
   if (i == [self.arrayOfID count] - 1 || i == [self.arrayOfID count]) // Its the last record to be stored 
   {  
       NSError *error;    
       if (![self.managedObjectContext save:&error]) 
       { 
        // Handle the error... 
        NSLog(@"Error in updating %@",error); 
       } 
   
       self.isUpdateImageCalled = NO; 
       [self performSelectorOnMainThread:@selector(removeProgressMeter) withObject:nil waitUntilDone:NO]; 
   
   } 
   // Update UI screen while in downloading process 
   [self performSelectorInBackground:@selector(updateProgressMeter:) withObject:[NSString stringWithFormat:@"%d",self.loopStartIndex+i+1]]; 
   } 
   } 
   

如果我没有释放responseData然后我的应用程序显示我记忆警告，并得到了坠毁。如果我发布了，那么[NSConcreteMutableData release]：发送消息发送到解除分配的实例0x1e931de0错误发生。

如何优化我的代码。任何人都可以在我的代码中建议我并重写并制作精致的代码。

请帮我一把。

Answer 1

您的responseData返回sendSynchronousRequest是autoreleased因此你不应该自己释放它。对于第一眼，我没有看到代码中的内存泄漏。有可能您的应用程序实际上使用太多内存，而不会泄漏它。尝试把一个自动释放池的内部进行循环：

for (...) { 
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; 

    // your original code with a lot of autoreleased objects 

    [pool release]; 
} 

如果一个自动释放池内包装你的代码，所有发送包裹内autorelease消息的所有对象将被真正发布的时候池本身是发布：这种方式可以在每个循环中清除内存。

另请参阅文档中的Using Autorelease Pools，它特别提到您应该在“如果您编写创建许多临时对象的循环”的情况下使用它们。