# 模糊效果

### 需求說明
iOS 14 beta版測試時，發現Blur的 private key無法使用...


### 
[github](https://github.com/touyu/BlurKit)

label.bk.addBlur(blurRadius: 3, colorTint: .white, colorTintAlpha: 0.4)
imageView.bk.addBlur(blurRadius: 4, colorTint: .white, colorTintAlpha: 0.2)
view.bk.removeBlur()
view.bk.isBlurHidden = true // or false


## Private API
- iPhone中的API
1. Published API(Documented API)
2. Private API：PrivateFrameworks框架中的API
3. UnPublished API(Undocumented API)：放在Frameworks框架中，但是卻沒有在官方文件中有使用說明、程式碼介紹等記錄的API

## VisualEffect + Animator

// 動畫
private let animator = UIViewPropertyAnimator(duration: 0.1, curve: .linear, animations: nil)

// 遮罩
private let visualEffectView = UIVisualEffectView(effect: nil)
    
/// 模糊程度
private let blurPercentage: CGFloat = 0.15
    
/// 設定blurEffectView的範圍與模糊程度
private func setupVisualBlurEffectView() {
        
    contentView.addSubview(visualEffectView)
    visualEffectView.isUserInteractionEnabled = false
    visualEffectView.translatesAutoresizingMaskIntoConstraints = false
    NSLayoutConstraint.activate([
        visualEffectView.topAnchor.constraint(equalTo: contentView.topAnchor),
        visualEffectView.leadingAnchor.constraint(equalTo: contentView.leadingAnchor),
        visualEffectView.trailingAnchor.constraint(equalTo: contentView.trailingAnchor),
        visualEffectView.bottomAnchor.constraint(equalTo: contentView.bottomAnchor)
    ])
    animator.fractionComplete = blurPercentage
}
    
/// 移除blurEffectView
func removeVisualBlurEffectViewIfNeed() {
    for subview in contentView.subviews where subview.isKind(of: UIVisualEffectView.self) {
        subview.removeFromSuperview()
        return
    }
}
    
override func awakeFromNib() {
    super.awakeFromNib()
    animator.addAnimations {
        // 完成狀態
        self.visualEffectView.effect = UIBlurEffect(style: .regular)
    }
}
    
/// 準備reuse
override func prepareForReuse() {
    removeVisualBlurEffectViewIfNeed()
    animator.stopAnimation(true)
    if animator.state == .stopped {
        animator.finishAnimation(at: .current)
    }
}
    
deinit {
    animator.stopAnimation(true)
    if animator.state == .inactive {
        animator.finishAnimation(at: .current)
    }
}

/// Animator若在完成之間就離開，會有NSInternalInconsistencyException的狀況
/// reason: 'It is an error to release a paused or stopped property animator. Property animators must either finish animating or be explicitly stopped and finished before they can be released.'
/// reason: 'finishAnimationAtPosition: should only be called on a stopped animator!'
/// 以上錯誤說明
/// 1. 釋放掉動畫前，必需明確的'停止'或是'完成'才能釋放
/// 2. finishAnimation只能在stopAnimation之後呼叫
private func finishAnimator() {
    animator.stopAnimation(true)
    if animator.state == .stopped {
        animator.finishAnimation(at: .current)
    }
}

## 待解決問題
- 加入Notification後發現，在didEnterBackgroundNotification時，畫面會開始變模糊
- 若在didEnterBackgroundNotification下斷點，就會正常