objective-c - 通过 OperationQueue 加载 UIImageView 的问题

Question

我使用 NSOperationQueue 加载 UIImageView。

加载从 Internet 获取图像，然后将其添加到图像视图。我遇到的问题是该方法完成但图像视图需要大约 3 秒后才能实际显示图像或从超级视图中删除图像视图......

- (void)viewDidLoad { NSLog(@"AirportDetailView: viewDidLoad");
    [super viewDidLoad];
    [self.activity startAnimating];
    self.queue = [NSOperationQueue new];
    NSInvocationOperation *operation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(loadImage) object:NULL]; 
    [self.queue addOperation:operation]; 
    [operation release];
}

-(void)loadImage {
        [myAp ImageForAp];

        NSLog(@"ImageFor Ap Ended, %@",myAp.ApDiagram);

        [self.activity stopAnimating];

        if (myAp.ApDiagram==NULL) {
            NSLog(@"Finally Gets Here");
            [self.Diagram removeFromSuperview];
        }
        else {
            NSLog(@"Finally Gets Here with Diag");
            [self.Diagram setBackgroundImage:myAp.ApDiagram forState:UIControlStateNormal];
        }

    }

NSLOG 显示前两个日志语句之间的延迟大约 3 秒无法理解为什么....

用我的最新代码更新......

-(void)loadImage {

    [myAp ImageForAp];

    NSLog(@"ImageFor Ap Ended, %@",myAp.ApDiagram);

    [self performSelectorOnMainThread:@selector(UpdateUI) withObject:nil waitUntilDone:NO];
}

-(void)UpdateUI {

    [self.activity stopAnimating];

    if (myAp.ApDiagram==NULL) {
        NSLog(@"Finally Gets Here");
        [self.Diagram removeFromSuperview];
    }
    else {
        NSLog(@"Finally Gets Here with Diag");
        [self.Diagram setBackgroundImage:myAp.ApDiagram forState:UIControlStateNormal];
    }
}

Answer 1

确保该loadImage方法正在主线程上运行。所有 UI 操作都需要在主线程上进行才能按预期工作。您的代码需要与此类似。

-(void)loadImage {
    [myAp ImageForAp];
    [self performSelectorOnMainThread:@selector(UpdateUI) withObject:nil waitUntilDone:NO];
}

-(void)UpdateUI {
    [self.activity stopAnimating];

    if (myAp.ApDiagram==NULL) {
        [self.Diagram removeFromSuperview];
    }
    else {
        [self.Diagram setBackgroundImage:myAp.ApDiagram forState:UIControlStateNormal];
    }
}

viewDidLoad 内部也可能存在内存泄漏。

self.queue = [NSOperationQueue new];应该改为

self.queue = [[[NSOperationQueue alloc] init] autorelease];