我如何处理多个复选框在MVVM模式
本文关键字：复选框 MVVM 模式 何处理 处理 | 更新日期: 2023-09-27 18:09:57
WPF中的绑定复选框是常见的问题，但我仍然没有找到初学者容易遵循的示例代码。我在WPF中有一个复选框列表来选择最喜欢的运动名称。在我的例子中，复选框的数量是静态的。谁能告诉我如何实现这个问题的ViewModel ?
FavoriteSportsView.xaml:
<StackPanel Height="50" HorizontalAlignment="Left" VerticalAlignment="Top"
Width="150">
<CheckBox IsChecked="{Binding IsChecked, Mode=TwoWay}"
Command="{Binding Path=SportsResponseCommand}"
CommandParameter="Football"
Content="Football"
Margin="5" />
<CheckBox IsChecked="{Binding IsChecked, Mode=TwoWay}"
Command="{Binding Path=SportsResponseCommand}"
CommandParameter="Hockey"
Content="Hockey"
Margin="5" />
<CheckBox IsChecked="{Binding IsChecked, Mode=TwoWay}"
Command="{Binding Path=SportsResponseCommand}"
CommandParameter="Golf"
Content="Golf"
Margin="5" />
</StackPanel>
FavoriteSportsViewModel.cs
public class FavoriteSportsViewModel.cs {
//Since I am using the same IsChecked in all check box options, I found all check
//boxes gets either checked or unchecked when I just check or uncheck one option.
//How do i resolve this issue? I don't think i need seprate IsChecked for each
//check box option.
private bool _isChecked;
public bool IsChecked{
get {
return _isChecked;
}
set { if (value != _isChecked)
_isChecked = value;
this.OnPropertyChanged("IsChecked");
}
}
//How do i detect parameter in this method?
private ICommand _sportsResponseCommand;
public ICommand SportsResponseCommand
{
get
{
if (_sportsResponseCommand== null)
_sportsResponseCommand= new
RelayCommand(a => DoCollectSelectedGames(), p => true);
return _sportsResponseCommand;
}
set
{
_sportsResponseCommand= value;
}
}
private void DoCollectSelectedGames(){
//Here i push all selected games in an array
}
public abstract class ViewModelBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
我不确定如何在以上ViewModel中做以下操作:1. 我如何实现一个方法来处理我所有的选项?2. 如何检测每个复选框以查看是否选中3.我如何利用CommandParameter?4. 如何正确实现SportsResponseCommand
您的视图模型应该看起来像这样:
public class MyViewModel : INotifyPropertyChanged
{
//INotifyPropertyChanged implementation
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
//bindable property
private bool _football;
public bool Football
{
get { return _football; }
set
{
if (value != _football)
{
_football = value;
this.OnPropertyChanged("Football");
}
}
}
//... and the same for Golf and Hockey
}
然后通过设置DataContext属性将视图模型与视图关联(这很可能在后面的Window或UserControl代码中，尽管有很多方法可以实现这一点)。
最后，更新你的绑定，使它们看起来像:
<CheckBox IsChecked="{Binding Football, Mode=TwoWay}"
Content="Football"
Margin="5" />
<CheckBox IsChecked="{Binding Golf, Mode=TwoWay}"
Content="Football"
Margin="5" />
作为最后的注释，您不应该真的需要绑定Command属性—您可以编写任何您需要在视图模型的属性设置器中运行的代码。
我强烈建议你阅读这篇文章http://msdn.microsoft.com/en-us/magazine/dd419663.aspx
我在下面描述了一个解决方案，我试图不修改你的XAML代码，但这不是唯一的方法(或最好的方法)，但包含了所有必要的元素!
首先你需要你的模型我把它命名为Model_Sport
public class Model_Sport : INotifyPropertyChanged
{
#region Constructor
public Model_Sport(string name, ICommand command)
{
Name = name;
SportsResponseCommand = command;
}
#endregion
static readonly PropertyChangedEventArgs _NameEventArgs = new PropertyChangedEventArgs("Name");
private string _Name = null;
public string Name
{
get { return _Name; }
set
{
_Name = value;
OnPropertyChanged(_NameEventArgs);
}
}
static readonly PropertyChangedEventArgs _SportsResponseCommandEventArgs = new PropertyChangedEventArgs("SportsResponseCommand");
private ICommand _SportsResponseCommand = null;
public ICommand SportsResponseCommand
{
get { return _SportsResponseCommand; }
set
{
_SportsResponseCommand = value;
OnPropertyChanged(_SportsResponseCommandEventArgs);
}
}
static readonly PropertyChangedEventArgs _IsCheckedEventArgs = new PropertyChangedEventArgs("IsChecked");
private bool _IsChecked = false;
public bool IsChecked
{
get { return _IsChecked; }
set
{
_IsChecked = value;
OnPropertyChanged(_IsCheckedEventArgs);
}
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(PropertyChangedEventArgs eventArgs)
{
if (PropertyChanged != null)
{
PropertyChanged(this, eventArgs);
}
}
#endregion
}
现在你需要一种方法来委托你的命令"sportsresponseccommand"，DelegateCommand对象将帮助你做到这一点
public class DelegateCommand : ICommand
{
private readonly Action<object> _ExecuteMethod;
private readonly Func< object, bool> _CanExecuteMethod;
#region Constructors
public DelegateCommand(Action<object>executeMethod, Func<object, bool> canExecuteMethod)
{
if (null == executeMethod)
{
throw new ArgumentNullException("executeMethod", "Delegate Command Delegates Cannot Be Null");
}
_ExecuteMethod = executeMethod;
_CanExecuteMethod = canExecuteMethod;
}
public DelegateCommand(Action<object>executeMethod) : this(executeMethod, null) { }
#endregion
#region Methods
public bool CanExecute(object parameter)
{
if (_CanExecuteMethod == null) return true;
return _CanExecuteMethod(parameter);
}
public void Execute(object parameter)
{
if (_ExecuteMethod == null) return;
_ExecuteMethod(parameter);
}
bool ICommand.CanExecute(object parameter)
{
return CanExecute(parameter);
}
public event EventHandler CanExecuteChanged
{
add { CommandManager.RequerySuggested += value; }
remove { CommandManager.RequerySuggested -= value; }
}
void ICommand.Execute(object parameter)
{
Execute(parameter);
}
#endregion
}
现在是" ViewModel "
public class ViewModel
{
#region property
public Dictionary<string, Model_Sport> Sports { get; set; }
public DelegateCommand SportsResponseCommand { get; set; }
#endregion
public ViewModel()
{
Sports = new Dictionary<string, Model_Sport>();
SportsResponseCommand = new DelegateCommand(p => execute_SportsResponseCommand(p));
buildSports();
}
private void buildSports()
{
Model_Sport football = new Model_Sport("Football", SportsResponseCommand);
Model_Sport golf = new Model_Sport("Golf", SportsResponseCommand);
Model_Sport hockey = new Model_Sport("Hockey", SportsResponseCommand);
football.IsChecked = true; // just for test
Sports.Add(football.Name, football);
Sports.Add(golf.Name, golf);
Sports.Add(hockey.Name, hockey);
}
private void execute_SportsResponseCommand(object p)
{
// TODO :what ever you want
MessageBox.Show(p.ToString());
}
}
现在视图记得为你的窗口设置数据上下文公共主窗口(){
InitializeComponent();
this.DataContext = new ViewModel();
}
在XAML
中 <StackPanel HorizontalAlignment="Left" VerticalAlignment="Top" >
<CheckBox DataContext="{Binding Path=Sports[Football]}"
IsChecked="{Binding IsChecked, Mode=TwoWay}"
Command="{Binding Path=SportsResponseCommand}"
CommandParameter="Football"
Content="Football"
Margin="5" />
<CheckBox DataContext="{Binding Path=Sports[Hockey]}"
IsChecked="{Binding IsChecked, Mode=TwoWay}"
Command="{Binding Path=SportsResponseCommand}"
CommandParameter="Hockey"
Content="Hockey"
Margin="5" />
<CheckBox DataContext="{Binding Path=Sports[Golf]}" IsChecked="{Binding IsChecked, Mode=TwoWay}"
Command="{Binding Path=SportsResponseCommand}"
CommandParameter="Golf"
Content="Golf"
Margin="5" />
</StackPanel>
如果你只是想要一个属性在你的ViewModel得到更新时，IsChecked的变化，替换IsChecked绑定到一个布尔属性在你的ViewModel引发NotifyPropertyChanged的"集"
现在，如果你想在每次IsChecked更改时对3个复选框中的一个执行操作:
首先，将CommandParameter替换为"{Binding RelativeSource={RelativeSource Mode=Self}}"
在你的ViewModel(应该实现INotifyPropertyChanged)中，创建一个iccommand (SportsResponseCommand)，它接受一个CheckBox In参数。
在命令的方法中，检查复选框的内容，并检查"IsChecked"属性，然后对它们进行处理。
您可以通过使用
来分配视图模型 //for the view
partial class MainView:Window
{
InitializeComponent();
this.DataContext=new MainViewModel();
}
//ViewModel Code
public class MainViewModel: INotifyPropertyChanged
{
//INotifyPropertyChanged implementation
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
//bindable property
private bool _football;
public bool Football
{
get { return _football; }
set
{
if (value != _football)
{
_football = value;
this.OnPropertyChanged("Football");
}
}
}
//... and the same for Golf and Hockey
}`
，然后你可以在XAML中实现绑定
<CheckBox IsChecked="{Binding Football, Mode=TwoWay}"
Command="{Binding Path=SportsResponseCommand}"
CommandParameter="Football"
Content="Football"
Margin="5" />
<CheckBox IsChecked="{Binding Golf, Mode=TwoWay}"
Command="{Binding Path=SportsResponseCommand}"
CommandParameter="Football"
Content="Football"
Margin="5" />