Question

所以，我有一个元素，它有一个带2个参数的命令。

我之前使用我发现的代码片段做了这件事，但是在我的生活中不能记住如何做或者再次找到它。

所以，这是我之前创建的多值转换器：

public class MultiValueConverter : IMultiValueConverter
{

    public object Convert(object[] values, Type targetType,
    object parameter, CultureInfo culture)
    {
        return values.Clone();
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
    {
        return (value as string).Split(' ');
    }

}

现在，我需要在ICommand中分配我想要调用的函数。我通常使用类似于：

的行

enemyPopupTooltip = new RelayCommand(param => this.EnemyPopupTooltipEx(param),null);

然而，当它的多值时，这不会起作用。如何使用我的relay命令将2个参数（使用多值转换器）传递到我的函数中？

作为参考，这里是relaycommand类中的所有内容：

public class RelayCommand : ICommand
{
    /// <summary>
    /// Initializes a new instance of the <see cref="RelayCommand"/> class.
    /// </summary>
    /// <param name="execute">The execute.</param>
    public RelayCommand(Action<object> execute)
        : this(execute, null)
    {
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="RelayCommand"/> class.
    /// </summary>
    /// <param name="execute">The execute.</param>
    /// <param name="canExecute">The can execute.</param>
    public RelayCommand(Action<object> execute, Predicate<object> canExecute)
    {
        if (execute == null)
            throw new ArgumentNullException("execute");
        _execute = execute;
        _canExecute = canExecute;
    }

    /// <summary>
    /// Defines the method that determines whether the command can execute in its current state.
    /// </summary>
    /// <param name="parameter">Data used by the command.  If the command does not require data to be passed, this object can be set to null.</param>
    /// <returns>
    /// true if this command can be executed; otherwise, false.
    /// </returns>
    public bool CanExecute(object parameter)
    {
        return _canExecute == null ? true : _canExecute(parameter);
    }

    /// <summary>
    /// Occurs when changes occur that affect whether or not the command should execute.
    /// </summary>
    public event EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }

    /// <summary>
    /// Defines the method to be called when the command is invoked.
    /// </summary>
    /// <param name="parameter">Data used by the command.  If the command does not require data to be passed, this object can be set to null.</param>
    public void Execute(object parameter)
    {
        _execute(parameter);
    }

    /// <summary>
    /// Action
    /// </summary>
    private readonly Action<object> _execute;


    /// <summary>
    /// Predicate
    /// </summary>
    private readonly Predicate<object> _canExecute;

Answer 1

你说：

然而，当它的多值
时，这不会起作用

这个假设是错误的。它确实有效！

当您的多转换器返回值数组时，此数组将作为参数传递给Command.Execute方法。

- (UICollectionReusableView *)collectionView: (UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {
    _headerView= [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"RequestHeaderView" forIndexPath:indexPath];
    [self.searchController.searchBar removeFromSuperview];
    self.searchController = [[UISearchController alloc] initWithSearchResultsController:nil];
    self.searchController.searchResultsUpdater = self;
    self.searchController.dimsBackgroundDuringPresentation = NO;
    self.searchController.searchBar.delegate = self;
    self.definesPresentationContext = YES;
    [self.searchController.searchBar sizeToFit];
    [_headerView.searchView addSubview:self.searchController.searchBar];
    return _headerView;
}

然而，这是非常肮脏的方法。我猜你正在将一些UIElement传递给command参数。这违反了viewmodel的责任。考虑将需要引用UIElement的代码移动到代码隐藏。

Answer 2

只需将两个参数放入一个对象即可。您可以使用任何类型的集合或数组，但也许最简单的选择是使用IMultiValueConverter中的Tuple<T1, T2> Class：

if (values != null && values.Length >= 2)
{
    Tuple<Type1, Type2> yourTwoValues = new Tuple<Type1, Type2>(values[0], values[1]);
    return yourTwoValues;
}

然后，您可以将Tuple作为参数传递给ICommand，并在另一端提取单个值。

Answer 3

尝试使用新属性，在CommandParameter中进行多重操作并在ExecuteEnterCommand中进行处理。比如object[] arr = (object[])obj;

 public ICommand EnemyPopupTooltip
        {
            get
            {
                if (this.enemyPopupTooltip == null)
                {
                    this.enemyPopupTooltip = new RelayCommand<object>(this.ExecuteEnterCommand, this.CanExecuteEnterCommand);
                }

                return this.enemyPopupTooltip;
            }
        }


        private ICommand enemyPopupTooltip;

WPF Multibinding - 需要使用Relaycommand

3 个答案: