标签: dispatch-async

我正在尝试使用uiimage-from-animated-gif将一些GIF加载到我的UITableView单元格中.但问题是,每当我尝试从我的Cache加载图像时,单元格在滚动之前会暂停一点.

这是我正在使用的代码

postGif = (UIImageView *)[cell viewWithTag:104];

if ([[ImageCache sharedImageCache] DoesExist:post[@"gif"]] == true)
{
    image = [[ImageCache sharedImageCache] GetImage:post[@"gif"]];

    postGif.image = [UIImage animatedImageWithAnimatedGIFData:image];

}else
{
    dispatch_queue_t backgroundQueue = dispatch_queue_create("cacheImage", 0);

    dispatch_async(backgroundQueue, ^{

        NSData *imageData = [[NSData alloc] initWithContentsOfURL: [NSURL URLWithString:post[@"gif"]]];
        dispatch_async(dispatch_get_main_queue(), ^{

            // Add the image to the cache
            [[ImageCache sharedImageCache] AddImage:post[@"gif"] image:imageData];

            NSIndexPath* ind = [NSIndexPath indexPathForRow:0 inSection:indexPath.section];
            [self.feedTableView beginUpdates];
            [self.feedTableView reloadRowsAtIndexPaths:[NSArray arrayWithObject:ind] withRowAnimation:UITableViewRowAnimationNone];
            [self.feedTableView endUpdates];
        });
    });
}

postGif.layer.cornerRadius = 2.0;
postGif.layer.masksToBounds = YES;

[cell.contentView addSubview:postGif]; …

由于某种原因,我有一个dispatch_async线程,它崩溃,除非我有一个NSLog()方法在它前面执行.该块运行一个从数据库中检索用户名的方法.

崩溃:

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
    user_web_communicator *usrWeb = [[user_web_communicator alloc]init];
    NSString *author = [usrWeb getUsernameFromID:author_string];
    [_author_label setText:[NSString stringWithFormat:@"Author: %@",author]];
});

工作:

NSLog(@"Fetching author for id: %@",author_string);
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
    user_web_communicator *usrWeb = [[user_web_communicator alloc]init];
    NSString *author = [usrWeb getUsernameFromID:author_string];
    [_author_label setText:[NSString stringWithFormat:@"Author: %@",author]];
});

错误

2013-08-19 13:56:06.149 Poll Me[4995:c07] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '{

Run Code Online (Sandbox Code Playgroud)

行:AsyncImageView:0x827aa00.minX == 10 + 1*0x827b8d0.marker + -1*0x8281210.marker + 0.5*0x8281260.marker AsyncImageView:0x827aa00.minY == 27.5 + -1*0x827b910.marker + -1*0x82812a0. marker + 0.5*0x82812e0.marker + 0.5*0x82823f0.marker …

我正在使用文件夹/文件应用程序，用户可以在其中将文件下载到本地磁盘。每当用户下载文件时，我都想显示一个显示进度的下载栏。

为此，我创建了一个协议，该协议允许我的下载类和视图控制器进行通信：

协议：

protocol DownloadResponder : class {
    func downloadFinished()
    func downloadProgress(current:Int64, total:Int64)
}

下载类：

class fileDownloader: NSObject, NSURLSessionDelegate, NSURLSessionDownloadDelegate {

    //responder
    var responder : MyAwesomeDownloadResponder?

    init(responder : MyAwesomeDownloadResponder) {
        self.responder = responder
    }

    ...

    func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) {

        println("downloaded \(100*totalBytesWritten/totalBytesExpectedToWrite)")
        responder?.downloadProgress(totalBytesWritten, total: totalBytesExpectedToWrite)

    }

...

}

然后在我的视图控制器中，我有一个触发downloadProgress功能的下载按钮：

func downloadProgress(current:Int64, total:Int64) {
        let priority = DISPATCH_QUEUE_PRIORITY_DEFAULT
        dispatch_async(dispatch_get_global_queue(priority, 0)) {
            // do some task
            var currentProgress = 100 * current …

我有以下代码,我一直试图从swift 2转换为swift 3.这是我到目前为止所拥有的.

DispatchQueue.async(group: DispatchQueue.global(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0),execute: {
            self.controllerDelegate?.codeToRun(progressWindowViewController: self)
        })

我收到一个错误,指出无法使用类型(int,int)的参数列表调用'global'.我知道全局队列需要这个,除非他们在swift 3中改变它吗？在Swift 3中执行全局队列的正确方法是什么？

以前的Swift 2 Equivlent

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0),{
            self.controllerDelegate?.codeToRun(self)
        })

我使用AVAudioPlayer并将numberofloop设置为-1,因为我想在无限循环中播放音频.起初效果很好,但是在播放音轨的过程中,我连续得到了以下错误日志,我的音轨被停止了.

2017-02-22 10:08:28.863041 TestBridgingHeader [1092:30476] [aqme] 255:AQDefaultDevice(173):跳过输入流0 0 0x0

我正在使用两个媒体播放器来淡出淡出声音.我使用块玩这两个媒体播放器:

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{});

为什么我的音轨会停止,为什么会显示AQDefaultDevice错误日志？

我们最近修改了我们的线程机制,支持dispatch_async在大多数地方使用'(在做了很多关于NSOperation和dispatch_async的阅读之后)*.然后我们的代码开始在代码的各个部分与EXC_BAD_ACCESS崩溃,总是在dispatch_async(queue,...)部分,没有明确的模式.通常在20分钟后发生--2小时.

我们的dispatch_async块用于通知听众,如下所示:

NSMutableSet *_listeners; // Initialised elsewhere and filled with interested listeners
void(^block)(id listener); // Block to execute

@synchronized(_listeners) {
  for (id listener in _listeners) {
    dispatch_async_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); // We used different queues for different listeners, but showing only one type of queue here for brevity
    dispatch_async(queue, ^{ // CRASHING LINE
      block(listener);
    });
  }
}

常见的症状是:

• 发生在iOS10上,从未在iOS8上发生过
• 在调试期间发生但从未报告过生产

(这是一个自我回答的问题)

*我们喜欢简单dispatch_async,不需要阻止/依赖功能,NSOperationQueue我们很快就会转向C++,所以想保持低水平.

我有一组调度工作项，如何等到一项工作完成后再继续队列中的下一项工作？

func AsyncCalls(statusHandler: @escaping (String) -> Void){

    var dispatchWorkItems : [DispatchWorkItem] = []
    let categoryWorkItem = DispatchWorkItem {
        main {
        return  statusHandler("Loading categories ")
        }
        self.modelView.getCategories(completion: { data,error in
            main {
            if data.isEmpty {
            return  statusHandler("\(error )")
            }else{
            return  statusHandler("Done loading categories")
            }
            }
        })
    }

    let itemsWorkItem = DispatchWorkItem {
        main {
            return statusHandler("Loading Inventory ")
        }
        self.modelView.getInventory(completion: { data,error in
            main {
                if data.isEmpty {
                return  statusHandler("\(error )")
                }else{
                return  statusHandler("Done loading Inventory")
                }
            }
        })
    }


    dispatchWorkItems.append(categoryWorkItem) …

我有一个可以向上滑动的ViewController.单击"保存"时,它会向服务器发送请求.请求完成后,它会关闭ViewController.我将NSURLConnection切换到使用async和blocks(https://github.com/rickerbh/NSURLConnection-Blocks).解除ViewController现在抛出"线程2:程序接收信号:EXC_BAD_ACCESS".如果重要的话,我正在使用ARC.

- (IBAction) savePressed
{
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:@"http://api.com/items/create"]];

    //NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
    [NSURLConnection asyncRequest:request success:^(NSData *data, NSURLResponse *response) {
        [self close];
    } failure:^(NSData *data, NSError *error) {
        [self close];
    }];
}

- (void) close
{
    [self dismissViewControllerAnimated:YES completion:nil];
}

这是日志

2012-10-24 10:32:43.780 Prayrbox[22268:1703] bool _WebTryThreadLock(bool), 0x1f21fd90: Tried to obtain the web lock from a thread other than the main thread or the web thread. This may be a result of calling to UIKit …

在非ARC应用程序中,我有一个NSOperation子类,它由一个委托排队,看起来像:

// note that the delegate and element properties are retained

-(id)initWithDelegate:(id<SomeDelegate>)inDelegate element:(SomeElement *)inElement
{
    if (self = [super init])
    {
        [self setDelegate:inDelegate];
        [self setElement:inElement];
    }
}

-(void)dealloc
{
    [_delegate release];
    [_element release];
    [super dealloc];
}

-(void)main
{
    // do stuff

    dispatch_async(dispatch_get_main_queue(), ^{
         [[self delegate] doSomething:[self element]];
    });
}

由于[[self delegate] doSomething:[self element]]将在我的NSOperation对象可能被解除分配后被调用,在将此操作添加到队列之前,是否需要确保在委托中保留"element"？元素对象保留在应用程序的其他位置,但可能会在那里释放.我需要确保当我的代表从NSOperation收回它时,它仍然是一个有效的对象.

只是想知道在dispatch_async中调用它的行为是否会保留传递给它的参数.我当然可以使用NSInvocation和performSelectorOnMainThread来保留它.

我试图延迟不到一秒钟.我从网上找到了这段代码.然而,它不接受不到一秒的延迟.Swift中的Grand Dispatch Concept对我来说有点神秘.我应该如何修改此代码以创建0.3秒的延迟？

    let deadlineTime = DispatchTime.now() + .seconds(1) //how to get 0.3 seconds here
    DispatchQueue.main.asyncAfter(deadline: deadlineTime) {        
      //code here
    }

我正在尝试使恒星“呼吸”在一个循环中。变大然后变小，然后重复。我希望在我的应用程序仍在运行并响应时继续执行此操作。当我在应用程序中转到另一个视图时，我希望动画停止播放。

这就是我得到的

    override func viewDidLoad() {
    super.viewDidLoad()

    DispatchQueue.main.async {
            self.animateStars()
    }
}

func animateStars() {
  UIView.animate(withDuration: 4, animations : {
        self.star.transform = CGAffineTransform(scaleX: 2.5, y: 2.5)

    }) { finished in
        NSLog("Star is big. Finished = \(finished)")
    }

    UIView.animate(withDuration: 4, animations : {
        self.star.transform = CGAffineTransform(scaleX: 0.5, y: 0.5)

    }) { finished in
        NSLog("Star is small. Finished = \(finished)")
    }
}

这并不困难。而且，我不知道如何在用户单击带有segue的按钮时不让它在后台疯狂运行的情况下使其循环。

我在Objective C中找到了一种解决方案，但是我似乎无法理解如何将其转换为Swift 3.0。此处的示例：https : //stackoverflow.com/a/31978173/5385322

 [UIView animateWithDuration:1
                  delay:0
                options:UIViewKeyframeAnimationOptionAutoreverse | UIViewKeyframeAnimationOptionRepeat
             animations:^{
                 yourView.transform = CGAffineTransformMakeScale(1.5, 1.5);
             }
             completion:nil]; …