Question

我应该将大量图像加载到滚动视图上，我想这需要一些时间和记忆。所以，我使用一个单独的线程在后台加载这些图像。我使用了以下多线程方法

[NSThread detachNewThreadSelector:@selector(prepareSliderView) toTarget:self withObject:nil];

将图像加载到单独的线程上。在实现此方法时，我在GDB中收到以下消息

NSAutoreleaseNoPool(): Object 0x10647180 of class NSPathStore2 autoreleased with no pool in place - just leaking
NSAutoreleaseNoPool(): Object 0x10647300 of class NSPathStore2 autoreleased with no pool in place - just leaking
NSAutoreleaseNoPool(): Object 0x10646a00 of class NSCFString autoreleased with no pool in place - just leaking
NSAutoreleaseNoPool(): Object 0x10647480 of class NSPathStore2 autoreleased with no pool in place - just leaking
NSAutoreleaseNoPool(): Object 0x10646a20 of class UIImage autoreleased with no pool in place - just leaking

我不知道这意味着什么，因为我之前从未执行过此方法。所以，我的问题是

1 - 我应该使用一些自动释放池以及此方法

2 - 有没有其他方法可以加载大量图像而不会给主线加载大量负载

-(IBAction)prepareSliderView{
NSLog(@"Preparing slider view");

NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

int totalPages=[kbDataSource numberOfPagesInBook];
sliderScrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, self.view.frame.size.height-300, self.view.frame.size.width,200 )];
sliderScrollView.contentSize = CGSizeMake(totalPages*150+((totalPages-1)*10), 200); 
sliderScrollView.backgroundColor=[[UIColor blackColor] colorWithAlphaComponent:1.0];
thumbnailContentView = [[UIView alloc] initWithFrame:CGRectMake(10, 0, sliderScrollView.contentSize.width, sliderScrollView.contentSize.height)];

newPageSlider.continuous=YES;
newPageSlider.minimumValue=1;
newPageSlider.maximumValue=totalPages;

 thumbnailFrame = CGRectMake(0, 25, 120, 150);
 pageNumFieldFrame = CGRectMake(0, thumbnailFrame.size.height+10, thumbnailFrame.size.width, 50);
for(int i=1;i<totalPages;i++){
    thumbnailView = [[UIView alloc] initWithFrame:thumbnailFrame];
    thumbnailView.backgroundColor=[UIColor clearColor];
    UIButton *thumbnail = [[UIButton alloc] initWithFrame:thumbnailFrame];
    UILabel *pageNumField = [[UILabel alloc] initWithFrame:pageNumFieldFrame];
    pageNumField.backgroundColor=[UIColor clearColor];
    thumbnail.tag=i+1;
    thumbnailView.tag=i+1;

    id<PageDataSource> pd = [kbDataSource pageAtIndex:i];

    thumbnailFrame = CGRectMake(thumbnailFrame.origin.x+150+10, thumbnailFrame.origin.y, 120, 150);
    pageNumFieldFrame = CGRectMake(pageNumFieldFrame.origin.x+150+10, pageNumFieldFrame.origin.y, thumbnailFrame.size.width, 50);
    [thumbnail setBackgroundImage:[pd thumbnailImageForPageNumber:i] forState:UIControlStateNormal];
    pageNumField.text =[NSString stringWithFormat:@"Page %d",i];
    pageNumField.textColor=[UIColor whiteColor];
    [thumbnailContentView addSubview:thumbnailView];
    [sliderScrollView addSubview:pageNumField];
    [sliderScrollView addSubview:thumbnail];
    [sliderScrollView addSubview:thumbnailView];
    [sliderScrollView bringSubviewToFront:thumbnail];
    [sliderScrollView bringSubviewToFront:pageNumField];
    [self.view bringSubviewToFront:thumbnail];
    [thumbnailView release];
    [pageNumField release];
    [thumbnail release];
    [thumbnail addTarget:self action:@selector(navigateToPage:) forControlEvents:UIControlEventTouchUpInside];
    [pool release];
}

}

Answer 1

对于您在新线程中执行的每个 main 方法，无论是通过NSThread还是通过performsSelectorInBackground:，您都必须创建一个自动释放池，如下所示：

- (void)myBackgroundOperation
{
   NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

   // Do some work.

   // At the very end, release the pool.
   [pool release];
}

另请参阅：Why is there no autorelease pool when I do performSelectorInBackground

但是对于你的任务，我建议你也查看NSOperationQueue。例如，请参阅文章Cocoa Tutorial: NSOperation and NSOperationQueue。

Answer 2

作为documentation says：

aSelector负责的方法用于设置自动释放池新分离的线程和释放退出之前的那个池

因此，在您的prepareSliderView方法中，您需要创建并释放自动释放池：

NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

// some work

[pool release];

在iPad编程中使用多线程时出现问题（用于加载大量图像）

2 个答案: