以下两个元素在我的 ICommand 实现中以不同方式触发并导致问题。当实现为TextBox输入CanExecuteChanged(object parameter)时,parameter的值为null。当它为Button 进入同样的方法时,parameter 的值等于CommandParameter。
理想情况下,在这两种情况下,我都希望 CommandParameter 值不发送到 CanExecuteChanged,而只发送到 Execute。
ICommand 的实现
public event EventHandler CanExecuteChanged
{
add
{
canExecuteChanged += value;
CommandManager.RequerySuggested += value;
}
remove
{
canExecuteChanged -= value;
CommandManager.RequerySuggested -= value;
}
}
public bool CanExecute(object parameter)
{
if (parameter is bool)
{
this.canExecute = (bool)parameter;
}
return this.canExecute;
}
public void Execute(object parameter)
{
this.executeAction((T)parameter);
}
internal void RaiseCanExecuteChanged()
{
this.OnCanExecuteChanged();
}
private void OnCanExecuteChanged()
{
if (this.canExecuteChanged != null)
{
this.canExecuteChanged(this, EventArgs.Empty);
}
}
文本框
<TextBox Width="80" Margin="2,2,2,2" Text="{Binding LastName, UpdateSourceTrigger=PropertyChanged}" MaxLength="25">
<TextBox.InputBindings>
<KeyBinding Key="Enter" Command="{Binding SearchCommand}">
<KeyBinding.CommandParameter>
<s:Boolean>True</s:Boolean>
</KeyBinding.CommandParameter>
</KeyBinding>
</TextBox.InputBindings>
</TextBox>
按钮
<Button Margin="2,2,2,2" Padding="10,0,10,0" Content="Search">
<Button.InputBindings>
<MouseBinding Command="{Binding SearchCommand }" MouseAction="LeftClick">
<MouseBinding.CommandParameter>
<s:Boolean>True</s:Boolean>
</MouseBinding.CommandParameter>
</MouseBinding>
</Button.InputBindings>
</Button>
最佳答案
在这种情况下,尝试@JoshSmith
的ICommand
实现,对我来说这两个选项都很好:
中继命令
public class RelayCommand : ICommand
{
private readonly Action<object> _execute;
private readonly Predicate<object> _canExecute;
public RelayCommand(Action<object> execute)
: this(execute, null)
{
}
public RelayCommand(Action<object> execute, Predicate<object> canExecute)
{
if (execute == null)
{
throw new ArgumentNullException("execute");
}
_execute = execute;
_canExecute = canExecute;
}
public bool CanExecute(object parameter)
{
return _canExecute == null ? true : _canExecute(parameter);
}
public event EventHandler CanExecuteChanged
{
add
{
CommandManager.RequerySuggested += value;
}
remove
{
CommandManager.RequerySuggested -= value;
}
}
public void Execute(object parameter)
{
_execute(parameter);
}
}
搜索命令
private RelayCommand _searchCommand = null;
public ICommand SearchCommand
{
get
{
if (_searchCommand == null)
{
_searchCommand = new RelayCommand(param => this.Search(param), param => true);
}
return _searchCommand;
}
}
private void Search(object param)
{
bool parameter = (bool)param;
if (parameter)
{
MessageBox.Show("Pressed the Enter Key");
}
}
关于c# - Key Input Bindings 与 CommandParameter 用法伯顿绑定(bind),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/22262986/