DispatchQueue main 未被调用

Question

我有一个执行计算和动画的异步任务，当动画开始时，队列暂停，当动画结束时，队列恢复。但由于某种原因，DispatchQueue.main.sync 从未被调用。

self.someQueue = DispatchQueue(label: "Animation", qos: .background, attributes: DispatchQueue.Attributes.concurrent)
    for index in stride(from: volumeObjects.count, to: -1, by: -1) {
        mainAsyncQueue.sync{
            self.dynamicViewModel.currentPercentile = Float(index)/Float(volumeObjects.count)
            self.currentObjectIndex = index
            print(index)

            DispatchQueue.main.sync {
                UIView.animate(withDuration: 1, animations: {
                    self.updateViewModelDynamicViewModel()
                }, completion: { (finished) in
                    self.someQueue.resume()
                })
            }
            self.someQueue.suspend()
        }
    }

这只是小计算，我会用它来解决比这更复杂的任务

Answer 1

我假设这段代码在主线程中。

如果是这样，您已同步到后台线程并尝试从那里同步回 DispatchQueue.main。但是那个队列在它可以做任何事情之前正在等待后台一个return。

Answer 2

感谢 Lou Franco 的回答，我做了一些修改：

DispatchQueue.global().async {
            self.someQueue = DispatchQueue(label: "Animation", qos: .background, attributes: DispatchQueue.Attributes.concurrent)
            for index in stride(from: volumeObjects.count, to: -1, by: -1) {
                self.someQueue.sync{
                    self.dynamicViewModel.currentPercentile = Float(index)/Float(volumeObjects.count)
                    self.currentObjectIndex = index
                    print(index)

                    DispatchQueue.main.sync {
                        UIView.animate(withDuration: 0.1, animations: {
                            self.updateViewModelDynamicViewModel()
                        }, completion: { (finished) in
                            if finished {
                                self.someQueue.resume()
                            }
                        })
                    }
                    self.someQueue.suspend()
                }
            }
        }

DispatchQueue main 未被调用

DispatchQueue main isn't called

grand-central-dispatch

ios

swift