UIFeedback Haptic引擎调用次数超过被激活次数

Question

我使用的是带有UIFeedback Haptic Engine的Wavid2.3，如：

let generator = UINotificationFeedbackGenerator()
generator.notificationOccurred(.Warning)

和

let generator = UIImpactFeedbackGenerator(style: .Heavy)
generator.impactOccurred()

今天我遇到了这样一个新的错误，却找不到问题。你有什么想法吗？

UIFeedbackHapticEngine _deactivate] called more times than the feedback engine was activated

详细信息：

Fatal Exception: NSInternalInconsistencyException
0  CoreFoundation                 0x1863e41c0 __exceptionPreprocess
1  libobjc.A.dylib                0x184e1c55c objc_exception_throw
2  CoreFoundation                 0x1863e4094 +[NSException raise:format:]
3  Foundation                     0x186e6e82c -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:]
4  UIKit                          0x18cc43fb8 -[_UIFeedbackEngine _deactivate]
5  UIKit                          0x18cad781c -[UIFeedbackGenerator __deactivateWithStyle:]

Answer 1

UIImpactFeedbackGenerator不是线程安全的，所以要确保同步调用generator.impactOccurred()，而不是在dispatch_async或其他异步线程中调用。

Answer 2

调用generator.impactOccurred()将在iOS 11.*上崩溃。您需要在主线程async上调用它。

let generator = UIImpactFeedbackGenerator(style: style)
generator.prepare()

DispatchQueue.main.async {
   generator.impactOccurred()
}

Answer 3

为了完成已经给出的答案:您想要做的要么是拥有一个OperationQueue或一个DispatchQueue，它总是用于调用FeedbackGenerator的函数。请记住，对于用例，您可能需要释放生成器，但最起码的例子是：

class HapticsService {

    private let hapticsQueue = DispatchQueue(label: "dev.alecrim.hapticQueue", qos: .userInteractive)

    typealias FeedbackType = UINotificationFeedbackGenerator.FeedbackType

    private let feedbackGeneator = UINotificationFeedbackGenerator()
    private let selectionGenerator = UISelectionFeedbackGenerator()

    func prepareForHaptic() {
        hapticsQueue.async {
            self.feedbackGeneator.prepare()
            self.selectionGenerator.prepare()
        }
    }

    func performHaptic(feedback: FeedbackType) {
        hapticsQueue.async {
            self.feedbackGeneator.notificationOccurred(feedback)
        }
    }

    func performSelectionHaptic() {
        hapticsQueue.async {
            self.selectionGenerator.selectionChanged()
        }
    }

}

这在很大程度上解决了我们生产中的相关问题。