04. WPF MVVM(3) RelayCommand

2020/08/21 - [WPF] - 02. WPF MVVM(1) View-ViewModel 연결

2020/08/21 - [WPF] - 03. WPF MVVM(2) INotifyPropertyChanged

 

View에서 일어나는 이벤트 가져오기

 

메뉴가 선택하면 다음과 같은 이벤트가 실행된다 해보자.

<Menu Background="Transparent" FontSize="16pt">
	<MenuItem Header="기본 정보" Command="{Binding BasicsButtonCommand}" />
</Menu>

 

ViewModel에 다음과 같이 설정한다. BasicsButtonCommand 이름에 주목하자.

public AllotmentView ViewWindow { get; set; } 

public DataTable Grade1Grid { get { return grade1Grid; } set { grade1Grid = value; OnPropertyChanged(); } } 
public DataRowView GradeRowView { set { GradeGrideClick(value); OnPropertyChanged(); } }

public ICommand BasicsButtonCommand { get; set; }

public AllotmentViewModel(AllotmentView viewWindow)
{
	this.ViewWindow = viewWindow;

	BasicsButtonCommand = new RelayCommand<Button>(BasicsClick, CanExcuteMethod);
}

private void BasicsClick(Button sender)
{
	//이벤트
}

 private bool CanExcuteMethod(object arg) 
 { 
   //활성화 
   return true; 
 }

 

public class RelayCommand<T> : ICommand
    {
        private Action<T> execute;

        private Predicate<object> canExecute;

        private event EventHandler CanExecuteChangedInternal;

        public RelayCommand(Action<T> execute)
            : this(execute, DefaultCanExecute)
        {
        }

        public RelayCommand(Action<T> execute, Predicate<object> canExecute)
        {
            this.execute = execute ?? throw new ArgumentNullException("execute");
            this.canExecute = canExecute ?? throw new ArgumentNullException("canExecute");
        }

        public event EventHandler CanExecuteChanged
        {
            add
            {
                CommandManager.RequerySuggested += value;
                this.CanExecuteChangedInternal += value;
            }

            remove
            {
                CommandManager.RequerySuggested -= value;
                this.CanExecuteChangedInternal -= value;
            }
        }

        public bool CanExecute(object parameter)
        {
            return this.canExecute != null && this.canExecute(parameter);
        }

        public void Execute(object parameter)
        {
            this.execute((T)parameter);
        }

        public void OnCanExecuteChanged()
        {
            CanExecuteChangedInternal?.Invoke(this, EventArgs.Empty);
        }

        public void Destroy()
        {
            this.canExecute = _ => false;
            this.execute = _ => { return; };
        }

        private static bool DefaultCanExecute(object parameter)
        {
            return true;
        }
    }

    public class RelayCommand : ICommand
    {
        private Action execute;

        private Func<bool> canExecute;

        private event EventHandler CanExecuteChangedInternal;

        public RelayCommand(Action execute)
            : this(execute, DefaultCanExecute)
        {
        }

        public RelayCommand(Action execute, Func<bool> defaultCanExecute)
        {
            this.execute = execute;
            this.canExecute = defaultCanExecute;
        }

        public event EventHandler CanExecuteChanged
        {
            add
            {
                CommandManager.RequerySuggested += value;
                this.CanExecuteChangedInternal += value;
            }

            remove
            {
                CommandManager.RequerySuggested -= value;
                this.CanExecuteChangedInternal -= value;
            }
        }

        public bool CanExecute(object parameter)
        {
            return this.canExecute != null && this.canExecute();
        }

        public void Execute(object parameter)
        {
            this.execute();
        }

        public void OnCanExecuteChanged()
        {
            CanExecuteChangedInternal?.Invoke(this, EventArgs.Empty);
        }

        private static bool DefaultCanExecute()
        {
            return true;
        }
    }