NullReferenceException: 未将对象引用设置到对象的实例。
StackTrace:
   在 System.Windows.Interop.HwndKeyboardInputProvider.System.Windows.Input.IKeyboardInputProvider.AcquireFocus(Boolean checkOnly)
   在 System.Windows.Input.KeyboardDevice.TryChangeFocus(DependencyObject newFocus, IKeyboardInputProvider keyboardInputProvider, Boolean askOld, Boolean askNew, Boolean forceToNullIfFailed)
   在 System.Windows.Input.KeyboardDevice.Focus(DependencyObject focus, Boolean askOld, Boolean askNew, Boolean forceToNullIfFailed)
   在 System.Windows.Input.KeyboardDevice.Focus(IInputElement element)
   在 System.Windows.UIElement.Focus()
   在 Quicker.View.TextWindow.<OnLoaded>d__104.VIlZOu5M5Yo1NZl8ZAZl(Object )
   在 Quicker.View.TextWindow.<OnLoaded>d__104.MoveNext()
--- 引发异常的上一位置中堆栈跟踪的末尾 ---
   在 System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   在 System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   在 System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)