从背景加载图像

Question

我正在后台加载图像。使用此代码

-(void)backgroundImageLoading
{
    if(isGroupOrFriend)
    {
        NSAutoreleasePool *pool=[[NSAutoreleasePool alloc] init];

        for(NSDictionary *d in m_kwikiArray)
        {
            NSMutableDictionary *dict=[NSMutableDictionary dictionary];
            if([d valueForKey:@"UserImage"]!=nil && ![[d valueForKey:@"UserImage"] isEqualToString:@""])
            {
                UIImage *img=[UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[d valueForKey:@"UserImage"]]]];
                if(img!=nil)
                    [dict setObject:img forKey:@"UserImage"];
            }
            else 
                [dict setObject:@"No Image" forKey:@"UserImage"];
            //if([d valueForKey:@"imagePath"]!=nil && ![[d valueForKey:@"imagePath"] isEqualToString:@""] )
            //          [dict setObject:[UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[d valueForKey:@"imagePath"]]]] forKey:@"imagePath"];
            //      else 
            //          [dict setObject:@"NO Image" forKey:@"imagePath"];
            if([[d valueForKey:@"Transactions"] count]>0)
            {
                if([[[d valueForKey:@"Transactions"] objectAtIndex:0] valueForKey:@"UserThumbnail"]!= nil && ![[[[d valueForKey:@"Transactions"] objectAtIndex:0]valueForKey:@"UserThumbnail"] isEqualToString:@""])
                {
                    UIImage *img1=[UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[[[d valueForKey:@"Transactions"] objectAtIndex:0] valueForKey:@"UserThumbnail"]]]];
                    if(img1!=nil)
                        [dict setObject:img1 forKey:@"UserThumbnail1"];
                }
                else 
                    [dict setObject:@"NOImage" forKey:@"UserThumbnail1"];
            }
            else 
                [dict setObject:@"NOImage" forKey:@"UserThumbnail1"];
            if([[d valueForKey:@"Transactions"] count]>1)
            {
                if([[[d valueForKey:@"Transactions"] objectAtIndex:1] valueForKey:@"UserThumbnail"]!=nil && ![[[[d valueForKey:@"Transactions"] objectAtIndex:1] valueForKey:@"UserThumbnail"] isEqualToString:@""])
                {
                    UIImage *img2=[UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[[[d valueForKey:@"Transactions"] objectAtIndex:1] valueForKey:@"UserThumbnail"]]]];
                    if(img2!=nil) 
                        [dict setObject:img2 forKey:@"UserThumbnail2"];
                }
                else 
                    [dict setObject:@"NOImage" forKey:@"UserThumbnail2"];
            }
            else 
                [dict setObject:@"NOImage" forKey:@"UserThumbnail2"];
            [imageForGruopAndFriendArray addObject:dict];

        }
        //isReloadTable=YES;
        [mTable reloadData];
        [pool release];
    }
    else 
    {
        NSAutoreleasePool *pool=[[NSAutoreleasePool alloc] init];

        for(NSDictionary *d in m_kwikiArray)
        {
            NSMutableDictionary *dict=[NSMutableDictionary dictionary];
            if([d valueForKey:@"Illustration"]!=nil && ![[d valueForKey:@"Illustration"] isEqualToString:@""])
            {
                UIImage *img=[UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[d valueForKey:@"Illustration"]]]];
                if(img!=nil)
                    [dict setObject:img forKey:@"Illustration"];
            }

            else 
                [dict setObject:@"No Image" forKey:@"Illustration"];
            if([d valueForKey:@"imagePath"]!=nil && ![[d valueForKey:@"imagePath"] isEqualToString:@""] )
            {
                UIImage *img1=[UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[d valueForKey:@"imagePath"]]]];
                if(img1!=nil)
                    [dict setObject:img1 forKey:@"imagePath"];
            }
            else 
                [dict setObject:@"NO Image" forKey:@"imagePath"];
            if([[d valueForKey:@"Transactions"] count]>0)
            {
                if([[[d valueForKey:@"Transactions"] objectAtIndex:0] valueForKey:@"UserThumbnail"]!= nil && ![[[[d valueForKey:@"Transactions"] objectAtIndex:0]valueForKey:@"UserThumbnail"] isEqualToString:@""])
                {

                    UIImage *img2=[UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[[[d valueForKey:@"Transactions"] objectAtIndex:0] valueForKey:@"UserThumbnail"]]]];
                    if(img2!=nil)
                        [dict setObject:img2 forKey:@"UserThumbnail1"];
                }
                else 
                    [dict setObject:@"NOImage" forKey:@"UserThumbnail1"];
            }
            else 
                [dict setObject:@"NOImage" forKey:@"UserThumbnail1"];
            if([[d valueForKey:@"Transactions"] count]>1)
            {
                if([[[d valueForKey:@"Transactions"] objectAtIndex:1] valueForKey:@"UserThumbnail"]!=nil && ![[[[d valueForKey:@"Transactions"] objectAtIndex:1] valueForKey:@"UserThumbnail"] isEqualToString:@""])
                {
                    UIImage *img3=[UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[[[d valueForKey:@"Transactions"] objectAtIndex:1] valueForKey:@"UserThumbnail"]]]];
                    if(img3!=nil)
                        [dict setObject:img3 forKey:@"UserThumbnail2"];
                }
                else 
                    [dict setObject:@"NOImage" forKey:@"UserThumbnail2"];
            }
            else 
                [dict setObject:@"NOImage" forKey:@"UserThumbnail2"];
            [imageArray addObject:dict];

        }
        //isReloadTable=YES;
        [mTable reloadData];
        [pool release];
    }
}

这里我在每次图像加载后在方法中使用 reloadData，但它不会在滚动表格后加载图像显示。

我想在这些图片加载后立即显示它们。

请帮帮我。提前谢谢。

Answer 1

伊修，

试着用这个代替[mTable reloadData]:

[mTable beginUpdates];
[mTable endUpdates];

顺便说一句，很抱歉，这段代码完全不可读。

Answer 2

Ishu，您的代码的基本问题是您无法在辅助线程中通过 UIImage imageWithData API 加载图像。 UIKit APIS 只能在主线程中使用。您可以做的是下载项目并将它们保存到辅助线程中的文件中，但您仍然需要在主线程中加载该图像数据。如果您只想下载然后加载图像数据，您甚至不需要辅助线程，因为 NSURLConnection 类已经支持异步完成回调，下载会在后台线程中自动完成。

Answer 3

在[m_Table reloadData];的代码中添加这一行，我使用这一行

[m_Table performSelectorOnMainThread:@selector(reloadData) withObject:self waitUntilDone:NO];