本文要實現Android的toast效果， 同理實現loading框， 包括模態和非模態（即是否攔截控制元件的焦點）。 

1、 因為toast文字有長有短， 所有要動態判斷toast文字的寬度。

extension UILabel {
    //根據最大寬度計算高
    func getLableSize(text: String, maxWidth: CGFloat) -> CGRect {
        let maxSize = CGSize(width: maxWidth, height: 0)   //注意高度是0
        //    size = text.boundingRectWithSize(size2, options: NSStringDrawingOptions.UsesLineFragmentOrigin, attributes: attributes , context: nil);
        let size = text.boundingRect(with: maxSize, options: .usesLineFragmentOrigin,
                                     attributes: [NSFontAttributeName:self.font], context: nil)
        return size
    }
}

2、 按鈕的點選事件：

    @IBAction func clickButton2( sender: Any) {
        let toast = ToastView()
        toast.showLoadingDlg()
    }
    @IBAction func clickButton3( sender: Any) {
        let toast = ToastView()
        toast.showToast(text: "網路連線異常，請稍候再試", pos: .Bottom)
    }
    @IBAction func showToastTop( sender: Any) {
        let toast = ToastView()
        toast.showToast(text: "您的申請已受理，請耐心等待", pos: .Top)
    }
    @IBAction func showNoModal(
 
 sender: Any) {
        let toast = ToastView()
        toast.showToastExt(text: "非模態toast", pos: .Bottom)
    }

3、以顯示loading為例講解語法， 注意模態和非模態是根據window大小決定的。 如果window的大小跟應用根視窗大小一樣， 那麼就是模態， 反之是非模態。

 func showLoadingDlg() {
        let rootRect = UIApplication.shared.windows.first?.frame   //應用螢幕大小
        let container = UIView()   //全屏且透明，蓋在最上面， 可以自定義點選事件， 從而實現模態和非模態框效果。
        container.backgroundColor = UIColor.clear
        container.frame = rootRect!
        //新增中間矩形黑色區域, 80*80
        let bgLength = 90
        let bgView = UIView()  //黑色半透明方形區域
        bgView.frame = CGRect(x: Int((rootRect?.width)!/2) - bgLength/2,
                              y: Int((rootRect?.height)!/2) - bgLength/2,
                              width: bgLength,
                              height: bgLength)
        bgView.layer.cornerRadius = 10   //黑色矩形區域的角弧度
        bgView.backgroundColor = UIColor(hue: 0, saturation: 0, brightness: 0, alpha: 0.8)
        container.addSubview(bgView)   //全屏透明背景在中心位置新增矩形黑色區域
        //新增圈圈
        let indicatorLength: CGFloat = 50  //黑色矩形區域裡的旋轉
        let indicatorView = UIActivityIndicatorView(activityIndicatorStyle: .white)
        indicatorView.frame = CGRect(x: (rootRect?.width)!/2 - indicatorLength/2,
                                     y: (rootRect?.height)!/2 - indicatorLength/2 - 10,
                                     width: indicatorLength,
                                     height: indicatorLength)
        indicatorView.startAnimating()   //動畫
        container.addSubview(indicatorView)  //新增旋轉動畫view
        //新增文字
        let lableX = (rootRect?.width)!/2 - CGFloat(bgLength/2) + 5
        let lableY = (rootRect?.height)!/2 + indicatorLength/2 - 10
        let lableView = UILabel(frame: CGRect(x: Int(lableX),
                                              y: Int(lableY),
                                              width: bgLength-10,
                                              height: bgLength/2-Int(indicatorLength)/2-5))
        lableView.font = UIFont.systemFont(ofSize: 15)    //設定系統字型和字號
        lableView.textColor = UIColor.white
        lableView.text = "載入中"
        lableView.textAlignment = .center
        container.addSubview(lableView)
        //-------------測試程式碼-------------
        //let size = lableView.getLableSize(text: "網路異常，請稍候再試", maxWidth: 100)
        //-------------測試程式碼-------------
        let window = UIWindow()
        window.backgroundColor = UIColor.clear
        window.frame = rootRect!    //全屏大小
        window.center = CGPoint(x: (rootRect?.width)!/2, y: (rootRect?.height)!/2)
        window.windowLevel = UIWindowLevelAlert
        window.isHidden = false
        window.addSubview(container)
        //新增點選事件
        container.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(tapGesture(sender:))))
        bufWindows.append(window)
        perform(#selector(showFinished(sender:)), with: window, afterDelay: delay)
    }

4、toast和loading框都是window， 可以動態關閉， 就像gif圖裡演示的那樣點選window所在區域就可以關閉。

    //新增點選事件
    func tapGesture(sender: UITapGestureRecognizer) {
        print("點選uiview")
        //移除最後一個
        if bufWindows.count > 0 {
            bufWindows.removeLast()
        }
        NSObject.cancelPreviousPerformRequests(withTarget: self)  //可以關閉window， 如果註釋該語句則相當於蓋住了一層透明介面
    }