// 在視圖控制器Controller中
    // iPad OS鍵盤事件
    // 重寫系統方法return true
    override var canBecomeFirstResponder: Bool {
        return true
    }
    
    // 在控制器的viewDidAppear方法中讓當前控制器成為焦點
    override func viewDidAppear(_ animated: Bool) {
        becomeFirstResponder()
    }
    
    // =============================
    // 鍵盤的按下
    override func pressesBegan(_ presses: Set<UIPress>, with event: UIPressesEvent?) {
        for press in presses {
            guard let key = press.key?.characters else {
                continue
            }
            switch key {
            case "w":
                DebugLog("w")
            case "a":
                DebugLog("a")
            case "s":
                DebugLog("s")
            case "d":
                DebugLog("d")
            default:
                DebugLog("do nothing")
            }
        }
    }
    
    // 鍵盤的彈起
    override func pressesEnded(_ presses: Set<UIPress>, with event: UIPressesEvent?) {
        for press in presses {
            guard let key = press.key?.characters else {
                continue
            }
            switch key {
            case "w":
                DebugLog("w")
            case "a":
                DebugLog("a")
            case "s":
                DebugLog("s")
            case "d":
                DebugLog("d")
            default:
                DebugLog("do nothing")
            }
        }
    }
    
    // =============================
    // 重寫一些系統級快捷鍵的方法，例如此方法為 command + a 全選
    override func selectAll(_ sender: Any?) {
        DebugLog("點擊了全選")
    }
    
    // =============================
    // return方法為按鍵組合
    override var keyCommands: [UIKeyCommand]? {
        // 此方法設置按鈕組合，會一直調用方法
        let keyCommand = UIKeyCommand(input: "a", modifierFlags: .control, action: #selector(test))
        // 設置此鍵值，按鍵組合只響應一次方法
        keyCommand.setValue(NSNumber.init(value: false), forKey: "repeatable")
        return [
            keyCommand
        ]
    }
    
    // 測試方法
    @objc func test () {
        DebugLog("111哈哈哈")
    }