在使用手势识别器添加子视图时遇到 UI 故障问题

Posted 2023-03-13

【中文标题】在使用手势识别器添加子视图时遇到 UI 故障问题

【英文标题】：Having trouble with UI glitch while adding subviews with Gesture Recognizers

【发布时间】：2016-12-03 02:41:40

【问题描述】：

我正在开发一个应用程序，用户可以在其中滑动“卡片”，这些卡片基本上是填充了来自 API 的数据的 UIView。

当应用首次打开时，会创建卡片并将其作为子视图添加到父视图。每次用户刷卡时，卡片都会从 superview 中移除。

当用户刷卡时，会在后台创建和缓存更多卡片。

当用户在最后一张卡片上时，我将缓存的卡片添加到超级视图中，在当前显示的卡片后面。

问题是，当卡片被添加到超级视图时，我的手势识别器停止工作/出现故障（用户无法滑动）。几秒钟后，它再次开始工作，用户可以滑动。

如何阻止识别器出现故障？任何见解将不胜感激。

谢谢！

这是创建/添加卡片的代码 // 创建卡片 func createCards(firstCall:Bool)

    APICall.begin ()  (info) in

        DispatchQueue.main.async 
            for i in info 

                let frontView = frontView()
                let backView = backView()

                // Set up front and back views
                self.viewSetup(view: frontView)
                self.viewSetup(view: backView)

                // Set up card view 
                let view = cardView(frame: frame)
                view.addSubview(backView)
                view.addSubview(frontView)
                self.viewSetup(view: view)
                view.isHidden = true

                // function that add recognizer
                self.dragging(view: view)

                // cacheCard
                if !firstCall
                    self.cache.add(cardView: view)
                // add to view
                else
                    self.view.addSubview(view)
                

            

            // Reveal current card
            if firstCall 
                self.view.subviews.last?.isHidden = false
            

            print("DONE")
        
    

这是添加识别器/添加缓存的代码

// dragging gesture helper
func draggig(card: view)
    let gesture = UIPanGestureRecognizer(target: self, action: #selector(ViewController.wasDragged(_:)))
    view.addGestureRecognizer(gesture)
    view.isUserInteractionEnabled = true



// dragged gestrues
func wasDragged(_ gesture: UIPanGestureRecognizer)

    // Only allow dragging when front is showing
    if(showingFront)

        // Dragging code
        let helper = draggingBeganHelper(gesture: gesture)
        let card:UIView = helper[0] as! UIView
        var rotation:CGAffineTransform = helper[1] as! CGAffineTransform
        var stretch:CGAffineTransform = helper.last as! CGAffineTransform

        if gesture.state == UIGestureRecognizerState.ended 

            rotation = CGAffineTransform(rotationAngle: 0)
            stretch = rotation.scaledBy(x: 1, y: 1)

            //Remove card from superview
            card.removeFromSuperview()

            // Store cards in cache
            if(self.view.subviews.count == lastCardIndex + cardOffset)

                createCards(false)

            

            // When at the second to last card
            else if self.view.subviews.count == lastCardIndex+1
                if cardCacheArray.isEmpty 
                    createCards(true)
                
                else
                    DispatchQueue.main.async 
                        for i in cardCacheArray
                            self.view.insertSubview(i, belowSubview: self.view.subviews[lastCardIndex])
                        
                        self.cache.empty()
                    
                
            
        
    



func draggingBeganHelper(gesture: UIPanGestureRecognizer) -> [AnyObject]
    // Card dragging gesture setup
    let translation = gesture.translation(in: self.view)
    let card = gesture.view
    card?.center = CGPoint(x: (card?.center.x)! + translation.x, y: (card?.center.y)! + translation.y)
    let xFromCenter = (card?.center.x)! - self.view.bounds.width/2
    let scale = min(100/abs(xFromCenter),1)
    let rotation = CGAffineTransform(rotationAngle:  xFromCenter/200)
    let stretch = rotation.scaledBy(x: scale, y: scale)
    card?.transform = stretch

    return [card!,rotation as AnyObject,stretch as AnyObject]

【问题讨论】：

因为事情（但最终）以您想要的方式工作，这可能意味着您已经正确编码了“基线”。如果您可以发布一些代码供我们查看，将会有所帮助。

@dfd 添加了代码

【参考方案1】：

想通了。一次加载太多 UIView。更好更流畅的方法是不断回收两个 UIViews