在Xaml中，说到绑定，我们用的最多的应该就是ICommand了，通过Command实现ViewModel到View之间的命令处理，例如Button默认就提供了Command支持，如下
Xaml：
<Button Content="TestWithCommand" Command="{Binding TestCommand}" />
ViewModel
/// <summary>Provides a base implementation of the <see cref="ICommand"/> interface. </summary>
public abstract class CommandBase : ICommand
{
/// <summary>Gets a value indicating whether the command can execute in its current state. </summary>
public abstract bool CanExecute { get; }
/// <summary>Defines the method to be called when the command is invoked. </summary>
protected abstract void Execute();
/// <summary>Tries to execute the command by checking the <see cref="CanExecute"/> property
/// and executes the command only when it can be executed. </summary>
/// <returns>True if command has been executed; false otherwise. </returns>
public bool TryExecute()
{
if (!CanExecute)
return false;
Execute();
return true;
}
/// <summary>Occurs when changes occur that affect whether or not the command should execute. </summary>
public event EventHandler CanExecuteChanged;
void ICommand.Execute(object parameter)
{
Execute();
}
bool ICommand.CanExecute(object parameter)
{
return CanExecute;
}
}
/// <summary>Provides an implementation of the <see cref="ICommand"/> interface. </summary>
public class RelayCommand : CommandBase
{
private readonly Action _execute;
private readonly Func<bool> _canExecute;
/// <summary>Initializes a new instance of the <see cref="RelayCommand"/> class. </summary>
/// <param name="execute">The action to execute. </param>
public RelayCommand(Action execute)
: this(execute, null)
{ }
/// <summary>Initializes a new instance of the <see cref="RelayCommand"/> class. </summary>
/// <param name="execute">The action to execute. </param>
/// <param name="canExecute">The predicate to check whether the function can be executed. </param>
public RelayCommand(Action execute, Func<bool> canExecute)
{
if (execute == null)
throw new ArgumentNullException(nameof(execute));
_execute = execute;
_canExecute = canExecute;
}
/// <summary>Defines the method to be called when the command is invoked. </summary>
protected override void Execute()
{
_execute();
}
/// <summary>Gets a value indicating whether the command can execute in its current state. </summary>
public override bool CanExecute => _canExecute == null || _canExecute();
}
RelayCommand
public class MainPageViewModel
{
public ICommand TestCommand { get; private set; }
public MainPageViewModel()
{
TestCommand = new RelayCommand(TestCmd);
}
public void TestCmd()
{
Debug.WriteLine("TestCmd");
}
}
上面只是一个最简单的例子，但是如果需要绑定的方法很多的时候，就会有一大堆的ICommand属性定义，并且也需要初始化，代码看起来特别臃肿
下面我们使用Behavior代替Command完成方法的绑定
在WinRT中，Behavior是以组件的方法安装到VS上的，而在UWP上，官方并没有提供对应的组件，我们可以通过Nuget添加UWP版本的Behavior组件：
http://www.nuget.org/packages/Microsoft.Xaml.Behaviors.Uwp.Managed/
使用如下
Xaml
<Button Content="TestWithAction">
<interactivity:Interaction.Behaviors>
<core:EventTriggerBehavior EventName="Click">
<core:CallMethodAction TargetObject="{Binding}" MethodName="Test"/>
</core:EventTriggerBehavior>
</interactivity:Interaction.Behaviors>
</Button>
ViewModel
public class MainPageViewModel
{
public void Test()
{
Debug.WriteLine("test");
}
}
官方提供的Behavior更加灵活，可以自己配置事件名，和对应的方法名称，并且我们在ViewModel中不需要写ICommand等代码了，看起来更简洁明了，但是还有个问题，
有时候我们需要用到事件的参数，有时候我们需要用到触发事件的控件，有时候我们还需要控件对应的DataContext，而官方提供的库中并不提供带参数的方法，下面我们对其进行修改一下，让其支持参数传递，并且支持多参数
自定义一个支持参数Action
public class Parameter : DependencyObject
{
public static readonly DependencyProperty ValueProperty = DependencyProperty.Register(
"Value", typeof (object), typeof (Parameter), new PropertyMetadata(default(object)));
public object Value
{
get { return (object) GetValue(ValueProperty); }
set { SetValue(ValueProperty, value); }
}
}
Parameter
/// <summary>
/// 带参数的Action
/// </summary>
[ContentProperty(Name = "Parameters")]
public sealed class WdCallMethodAction : DependencyObject, IAction
{
public static readonly DependencyProperty MethodNameProperty = DependencyProperty.Register("MethodName",
typeof (string), typeof (WdCallMethodAction), new PropertyMetadata(null));
public static readonly DependencyProperty TargetObjectProperty = DependencyProperty.Register("TargetObject",
typeof (object), typeof (WdCallMethodAction), new PropertyMetadata(null));
public static readonly DependencyProperty ParametersProperty = DependencyProperty.Register(
"Parameters", typeof (ICollection<Parameter>), typeof (WdCallMethodAction),
new PropertyMetadata(new List<Parameter>()));
/// <summary>
/// 方法名：参数有?,eventArgs,sender,dataContext
/// eg：Test
/// eg：Test(?,?)
/// eg：Test(sender,?,?)
/// </summary>
public string MethodName
{
get { return (string) GetValue(MethodNameProperty); }
set { SetValue(MethodNameProperty, value); }
}
public ICollection<Parameter> Parameters
{
get { return (ICollection<Parameter>) GetValue(ParametersProperty); }
set { SetValue(ParametersProperty, value); }
}
public object TargetObject
{
get { return GetValue(TargetObjectProperty); }
set { SetValue(TargetObjectProperty, value); }
}
public object Execute(object sender, object parameter)
{
InvokeMethod(MethodName, sender, parameter, TargetObject, Parameters);
return true;
}
public void InvokeMethod(string methodName, object sender, object eventArgs, object dataContext,
ICollection<Parameter> parameters)
{
var start = methodName.IndexOf(‘(‘);
var end = methodName.IndexOf(‘)‘);
MethodInfo methodInfo;
if (start >= 0 && end >= 0)
{
var paras = methodName.Substring(start + 1, end - start - 1)
.Split(new[] {‘,‘, ‘ ‘}, StringSplitOptions.RemoveEmptyEntries);
methodName = MethodName.Substring(0, start);
var allParameter = new List<object>();
var enumerator = parameters.GetEnumerator();
foreach (var para in paras)
{
switch (para)
{
case "?":
enumerator.MoveNext();
allParameter.Add(enumerator.Current);
break;
case "eventArgs":
allParameter.Add(eventArgs);
break;
case "sender":
allParameter.Add(sender);
break;
case "dataContext":
allParameter.Add(dataContext);
break;
default:
throw new NotImplementedException(string.Format("没有实现该参数:{0}", para));
}
}
var paramCount = paras.Length;
methodInfo = TargetObject.GetType().GetRuntimeMethods()
.FirstOrDefault(m => Equals(m.Name, methodName) && m.GetParameters().Count() == paramCount);
methodInfo.Invoke(TargetObject, allParameter.ToArray());
}
else
{
methodInfo = TargetObject.GetType().GetRuntimeMethod(methodName, new Type[0]);
methodInfo.Invoke(TargetObject, null);
}
}
}
WdCallMethodAction
Xaml
<Button x:Name="btn" Content="TestWithActionAndParameter">
<interactivity:Interaction.Behaviors>
<core:EventTriggerBehavior EventName="Click">
<command:WdCallMethodAction TargetObject="{Binding}" MethodName="Test(eventArgs, sender, dataContext, ?,?)">
<command:Parameter Value="32"/>
<!-- 参数暂不支持绑定（下面方式为空）-->
<command:Parameter Value="{Binding ElementName=btn}"/>
</command:WdCallMethodAction>
</core:EventTriggerBehavior>
</interactivity:Interaction.Behaviors>
</Button>
ViewModel
public void Test(RoutedEventArgs eventArgs, FrameworkElement sender, MainPageViewModel dataContext, Parameter param1, object param2)
{
Debug.WriteLine("sender:{0}", sender);
Debug.WriteLine("eventArgs:{0}", eventArgs); Debug.WriteLine("dataContext:{0}", dataContext);
Debug.WriteLine("param1:{0}", param1);
Debug.WriteLine("param2:{0}", param2);
}
注：目前Parameter暂不支持绑定
demo
http://files.cnblogs.com/files/bomo/CommandInvokeDemo.zip
时间： 2024-08-10 04:17:13