我如何做出一个SwiftUI手势来在按下视图时保持运行代码 [英] How do I make a SwiftUI gesture that keeps running code while the view is pressed

问题描述

我正在尝试制作一个控制计数器的按钮.如果您点击它，则计数器将增加一.但是，如果您点击并按住它，我希望计数器在您按住它时每n秒上升一格，并继续这样做直到放开为止.

I am trying to make a button that controls a counter. If you tap it, the counter goes up by one. But if you tap and hold it, I want the counter to go up by one every n seconds while you are holding it and keep doing that until you let go.

如果我使用以下代码:

@GestureState var isDetectingLongPress = false
var plusLongPress: some Gesture {
    LongPressGesture(minimumDuration: 1)
        .updating($isDetectingLongPress) { currentstate, gestureState, _ in
            gestureState = currentstate
        }
        .onEnded { finished in
            print("LP: finished \(finished)")
        }
}

然后，一秒钟后 isDetectingLongPress 变为true，然后立即变为false.并且 onEnded 中的打印也会在1秒钟后被调用.

Then isDetectingLongPress becomes true after one second and then immediately becomes false. And the print in onEnded is called after 1 second as well.

我想要某种方式来保持调用代码，以在手指按下视图时不断更新计数器，而不仅仅是在检测到长按之后一次.

I want some way to keep calling code to continuously update a counter while the finger is pressing the view -- not just once after a long press is detected.

推荐答案

使用以下组合跟踪连续按下状态

Use instead the following combination to track continuous pressing down

通过Xcode 11.4/iOS 13.4测试

Tested with Xcode 11.4 / iOS 13.4

@GestureState var isLongPress = false // will be true till tap hold

var plusLongPress: some Gesture {
    LongPressGesture(minimumDuration: 1).sequenced(before:   
          DragGesture(minimumDistance: 0, coordinateSpace: 
          .local)).updating($isLongPress) { value, state, transaction in
            switch value {
                case .second(true, nil):
                    state = true
                   // side effect here if needed
                default:
                    break
            }
        }
}

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