Question

我正在尝试使用屏幕顶部的进度表向用户下载超过600个图像。我用一个淡化层屏蔽了我的屏幕以显示活动和进度。

我在中间收到内存警告消息，app崩溃了。

我到达循环的步骤是：

在app delegate上，我检查第一个核心数据表中是否有＆＃34; 0＆＃34; isImageAvailable bool字段中的值。
如果给我看一些计数（比如说600），我会用YES和NO选项显示并提醒。
开启是：[self performSelector：@selector（myDownload :) withObject：nil afterDelay：0.2];

在myDownload

中

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];

：

-(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]];
}
}

如果我没有发布responseData，那么我的应用会向我显示内存警告并崩溃。如果我发布了，[NSConcreteMutableData release]：发送到解除分配的实例0x1e931de0的消息发生错误。

如何优化我的代码。任何人都可以建议我使用我的代码和返工，并制作精致的代码。

请帮帮我。

Answer 1

responseData返回的sendSynchronousRequest已自动释放，因此您不应自行释放。乍一看，我没有在代码中看到内存泄漏。您的应用程序实际上可能会使用太多内存，而不会泄漏内存。尝试在您的for循环中放置一个自动释放池：

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

    // your original code with a lot of autoreleased objects

    [pool release];
}

如果您将代码包装在自动释放池中，发送的所有对象将在发布池本身时释放包含内的autorelease消息：这样您就可以清除每个循环中的记忆。

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

下载大量图像时出现内存泄漏问题

1 个答案: