Activity 当按下 navigationItem 按钮时指示器没有动画

Question

我尝试在按下 navigationItem 的按钮时触发 activity 指示器的动画。但是我发现 activity 指标没有旋转。我尝试将 scanerIndicator.startAnimating() 放到主线程，但是没有帮助。

代码收集了路由器打开的端口，我想在按下 navigationItem 按钮时开始旋转，并在 returned openPorts 时停止旋转。感谢 clue/hint 哪里有问题？

    override func viewDidLoad() {
        super.viewDidLoad()
        ...
        
        navigationItem.rightBarButtonItem = UIBarButtonItem(title: "Start", style: .plain, target: self, action: #selector(startScan))
        ...
    }

    @objc func startScan() {
        scanerIndicator.startAnimating()
        
        if let address = serverAddress.text, !address.isEmpty {
            if let start = Int(startPort.text!) {
                if let stop = Int(stopPort.text!) {
                    if start < stop {
                        openPorts = netUtility.scanPorts(address: address, start: start, stop: stop)
                        print("Open Open: \(openPorts)")
                        if !openPorts.isEmpty {
                            scanerIndicator.stopAnimating()
                            table.reloadData()
                        } else {
                            showErrorMessage(errorTitle: "Not at all", errorMessage: "No open ports were found")
                        }
                    } else {
                        showErrorMessage(errorTitle: "Range error", errorMessage: "Start port should be smaller than stop port")
                    }
                } else {
                    showErrorMessage(errorTitle: "Empty fields", errorMessage: "Please fill all the necessary data")
                }
            } else {
                showErrorMessage(errorTitle: "Empty fields", errorMessage: "Please fill all the necessary data")
            }
        } else {
            showErrorMessage(errorTitle: "Empty fields", errorMessage: "Please fill all the necessary data")
        }
    }

收集端口的代码：

   // MARK: - Port Scaner
    // Get number of threads for scan ports
    func getSegmentsQueues(min: Int, max: Int, maxPerSegment: Int) -> [[Int]] {
        
        var start: Int = min
        var portSegments = [[Int]]()
        
        while start <= max {
            var _portSegment = [Int]()
            
            for _ in 1...maxPerSegment {
                
                if start <= max {
                    _portSegment.append(start)
                }
                
                start += 1
            }
            
            portSegments.append(_portSegment)
        }
        
        return portSegments
    }


    // Crate queques for scan ports by segments
    func QueueDispatchPort(address: String, minPort: Int, maxPort: Int, segmentsQueues: (Int, Int, Int) -> [[Int]]) -> [Int] {
        var openPorts : [Int] = []
        let segmentPorts = segmentsQueues(minPort, maxPort, 1);
        
        let group = DispatchGroup()
        
        for segment in segmentPorts {
            group.enter()
            DispatchQueue.global().async {
                
                for port in segment {
                    let client = TCPClient(address: address, port: Int32(port))
                    switch client.connect(timeout: 2) {
                        case .success:
                            openPorts.append(port)
                        
                        case .failure(_):
                            print("port \(port) closed")
                    }
                    
                    client.close()
                }
                group.leave()
            }
        }
        
        group.wait()

        return openPorts
    }
    
    // Scans ports from an address and a range given by the user
    func scanPorts(address : String, start : Int, stop : Int) -> [Int] {
        let openPorts = QueueDispatchPort(
            address: address, minPort: start, maxPort: stop, segmentsQueues:
            getSegmentsQueues(min:max:maxPerSegment:))
        
        return openPorts
    }

代码更新，我将代码块（扫描端口）放在主线程上，这次删除了stopAnimating()。 activity 指标在长运行代码 return（DispatchQueue.main 中的内容）之后进行动画处理。还是不行...

@objc func startScan() {
        scanerIndicator.startAnimating()
        
        DispatchQueue.main.async { [self] in
            if let address = serverAddress.text, !address.isEmpty {
                if let start = Int(startPort.text!) {
                    if let stop = Int(stopPort.text!) {
                        if start < stop {
                            openPorts = netUtility.scanPorts(address: address, start: start, stop: stop)
                            print("Open Open: \(openPorts)")
                            if !openPorts.isEmpty {
                                table.reloadData()
                            } else {
                                showErrorMessage(errorTitle: "Not at all", errorMessage: "No open ports were found")
                            }
                        } else {
                            showErrorMessage(errorTitle: "Range error", errorMessage: "Start port should be smaller than stop port")
                        }
                    } else {
                        showErrorMessage(errorTitle: "Empty fields", errorMessage: "Please fill all the necessary data")
                    }
                } else {
                    showErrorMessage(errorTitle: "Empty fields", errorMessage: "Please fill all the necessary data")
                }
            } else {
                showErrorMessage(errorTitle: "Empty fields", errorMessage: "Please fill all the necessary data")
            }
        }
    }

Answer 1

有点难以理解您的代码在做什么，但我的猜测是即使您使用队列进行端口扫描，因为您使用的是 DispatchGroup，所以代码会阻塞直到所有端口扫描完成了。

如果您有执行以下操作的同步代码：

开始动画 activity 指标
执行 long-running 任务（在主线程上）
停止动画 activity 指标

那你就再也看不到动画了。问题是在您的代码 return 和您的应用程序访问其事件循环之前动画不会开始。

您需要像这样编写代码：

scanerIndicator.startAnimating()
DispatchQueue.main.async {
   //Do long-running task
   scanerIndicator.stopAnimating()
}

之所以可行，是因为在调用 startAnimating() 之后，您将异步调用添加到主调度队列（在主线程上），然后是 return。您的应用程序的函数调用堆栈全部 return，您的应用程序访问事件循环，并且 activity 指示器开始旋转。然后系统选择您添加到主队列的异步任务并开始运行该任务。最后，当您的 long-running 任务完成时，您关闭 activity 指示器（在内部调用的代码中 async() 电话。

Answer 2

终于，终于让这段代码生效了，DispatchQueue真是烧了一整天的脑子！

我的修复流程：

    func abc() {
        activityIndicator.startAnimating()
        
        DispatchQueue.global(qos: .default).async {
            // put your heavy code here
            
            DispatchQueue.main.async {
                // UI code must be on main thread
                activityIndicator.stopAnimating()
            }
        }
    }

我做什么？

首先，我将两个端口扫描代码合并为一个函数。
将long-time消费代码放入DispatchQueue.global(qos: .default).async。我首先尝试使用主线程，但它失败了，而且 long-running 代码应该在后台线程中。 global() 是后台线程吗？稍后我会挖掘更多:)
当这段繁重的代码完成时，使用@escaping completionHandler 作为回调将 openPorts 提供给调用者。因为在这种情况下你不能使用 return 值，因为我们不知道繁重的代码何时完成，所以我们使用回调将参数传递回调用者。

    // Scans ports from an address and a range given by the user
    func scanPorts(address : String, start : Int, stop : Int, completion: @escaping ([Int]) -> ()) {
        
        DispatchQueue.global(qos: .default).async {
            for port in start...stop {
                let client = TCPClient(address: address, port: Int32(port))
                switch client.connect(timeout: 2) {
                    case .success:
                        self.openPorts.append(port)
                        print("HH: port: \(self.openPorts)")
                    case .failure(_):
                        print("port \(port) closed")
                }
                client.close()
            }
            completion(self.openPorts)
        }
    }

调用者：请记住将 UI 代码放在主线程上。

@objc func startScan() {
        scanerIndicator.startAnimating()
        view.endEditing(true)
        self.view.isUserInteractionEnabled = false
        
        if let address = serverAddress.text, !address.isEmpty {
            if let start = Int(startPort.text!) {
                if let stop = Int(stopPort.text!) {
                    if start < stop {
                        netUtility.scanPorts(address: address, start: start, stop: stop) { [self] (availablePorts) in
                            openPorts = availablePorts
                            print("$Open ports: \(self.openPorts)")
                            if !openPorts.isEmpty {
                                DispatchQueue.main.async {
                                    table.reloadData()
                                    self.scanerIndicator.stopAnimating()
                                }
                            } else {
                                showErrorMessage(errorTitle: "Not at all", errorMessage: "No open ports were found")
                            }
                        }
                    } else {
                        showErrorMessage(errorTitle: "Range error", errorMessage: "Start port should be smaller than stop port")
                    }
                } else {
                    showErrorMessage(errorTitle: "Empty fields", errorMessage: "Please fill all the necessary data")
                }
            } else {
                showErrorMessage(errorTitle: "Empty fields", errorMessage: "Please fill all the necessary data")
            }
        } else {
            showErrorMessage(errorTitle: "Empty fields", errorMessage: "Please fill all the necessary data")
        }
    }

Activity 当按下 navigationItem 按钮时指示器没有动画

Activity Indicator is not animated when press navigationItem button

swift

uiactivityindicatorview