Windows Phone 7 MVVM模式通讯方式之实现Command

Windows
Phone 7 MVVM模式通讯方式之实现Command

MVVM模式的View与ViewModel的三大通讯方式：Binding
Data（实现数据的传递）、Command（实现操作的调用）和Attached Behavior（实现控件加载过程中的操作）。

(1)Windows Phone 7 MVVM模式通讯方式之实现Binding Data。

(2)Windows
Phone 7 MVVM模式通讯方式之实现Command。

(3)Windows Phone 7 MVVM模式通讯方式之实现Attached Behavior。

下面通过一个实例实现MVVM模式的Command通讯

（1）MainPage.xaml文件的代码,实现View层

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<phone:PhoneApplicationPage

    x:Class="CommandDemo.MainPage"

    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

    xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"

    xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"

    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"

    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

    xmlns:my="clr-namespace:CommandDemo.ViewModel"

    xmlns:my_Interactivity="clr-namespace:CommandDemo.Command"

    xmlns:Custom="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
xmlns:ic="clr-namespace:Microsoft.Expression.Interactivity.Core;assembly=Microsoft.Expression.Interactions"

    mc:Ignorable="d" d:DesignWidth="480" d:DesignHeight="768"

    FontFamily="{StaticResource
PhoneFontFamilyNormal}"

    FontSize="{StaticResource
PhoneFontSizeNormal}"

    Foreground="{StaticResource
PhoneForegroundBrush}"

    SupportedOrientations="Portrait" Orientation="Portrait"

    shell:SystemTray.IsVisible="True">

    <!--设置整个页面的上下文数据DataContext为RadiusViewModel-->

    <phone:PhoneApplicationPage.DataContext>

        <my:RadiusViewModel/>


    </phone:PhoneApplicationPage.DataContext>

    <Grid x:Name="LayoutRoot" Background="Transparent">


        <Grid.RowDefinitions>


            <RowDefinition Height="Auto"/>

            <RowDefinition Height="*"/>

        </Grid.RowDefinitions>


        <StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,17,0,28">

            <TextBlock x:Name="ApplicationTitle" Text="MY APPLICATION" Style="{StaticResource PhoneTextNormalStyle}"/>

            <TextBlock x:Name="PageTitle" Text="Command" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>

        </StackPanel>


        <Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">

            <Ellipse Fill="Red"

                     Height="{Binding Radius}" Width="{Binding Radius}"

                     HorizontalAlignment="Left" Margin="119,84,0,0" Name="ellipse1" Stroke="Black" StrokeThickness="1" VerticalAlignment="Top" />

            <Button Content="小" Height="72" HorizontalAlignment="Left" Margin="0,385,0,0" Name="button1" VerticalAlignment="Top" Width="160">

                <Custom:Interaction.Triggers>

                    <Custom:EventTrigger EventName="Click">

                        <my_Interactivity:ExecuteCommandAction CommandName="MinRadius"/>


                    </Custom:EventTrigger>


                </Custom:Interaction.Triggers>

            </Button>

            <Button Content="中" Height="72" HorizontalAlignment="Left" Margin="149,384,0,0" Name="button2" VerticalAlignment="Top" Width="160" >

                <Custom:Interaction.Triggers>

                    <Custom:EventTrigger EventName="Click">

                        <my_Interactivity:ExecuteCommandAction CommandName="MedRadius"/>


                    </Custom:EventTrigger>


                </Custom:Interaction.Triggers>

            </Button>

            <Button Content="大" Height="72" HorizontalAlignment="Left" Margin="299,382,0,0" Name="button3" VerticalAlignment="Top" Width="160" >

                <Custom:Interaction.Triggers>

                    <Custom:EventTrigger EventName="Click">

                        <my_Interactivity:ExecuteCommandAction  CommandName="MaxRadius"/>


                    </Custom:EventTrigger>


                </Custom:Interaction.Triggers>

            </Button>

        </Grid>

    </Grid>

</phone:PhoneApplicationPage>

（2）RadiusViewModel.cs文件的代码,实现ViewModel层

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using
System;

using
System.Windows.Input;

using
System.ComponentModel;

using
Microsoft.Expression.Interactivity.Core;


namespace CommandDemo.ViewModel

{

    public
class RadiusViewModel : INotifyPropertyChanged

    {

        private
Double radius;

        public
RadiusViewModel()

        {

            Radius = 0;


            MinRadius =
new ActionCommand(p => Radius = 100);

            MedRadius =
new ActionCommand(p => Radius = 200);

            MaxRadius =
new ActionCommand(p => Radius = 300);

        }

        public
event PropertyChangedEventHandler PropertyChanged;

        public
ICommand MinRadius

        {

            get; private set;

        }

        public
ICommand MedRadius

        {

            get;

            private set;

        }

        public
ICommand MaxRadius

        {

            get;

            private set;

        }

        public
Double Radius

        {

            get

            {


                return radius;


            }


            set

            {


                radius =
value;

                OnPropertyChanged("Radius");

            }


        }

        protected virtual void
OnPropertyChanged(string propertyName)


        {

            var
propertyChanged = PropertyChanged;

            if(propertyChanged !=
null)


                propertyChanged(this, new PropertyChangedEventArgs(propertyName));

        }

    }

}

（3）ExecuteCommandAction.cs类，实现Command操作

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using
System;

using
System.Windows;

using
System.Windows.Input;

using
System.Windows.Interactivity;

using
System.Reflection;

namespace CommandDemo.Command

{

    public
class ExecuteCommandAction :
TriggerAction<FrameworkElement>

    {

        public
static readonly DependencyProperty CommandNameProperty =

             DependencyProperty.Register("CommandName",
typeof(string), typeof(ExecuteCommandAction), null);

        public
static readonly DependencyProperty CommandParameterProperty =

            DependencyProperty.Register("CommandParameter",
typeof(object), typeof(ExecuteCommandAction), null);

        protected override void
Invoke(object parameter)


        {

            if
(AssociatedObject == null)

                return;

            ICommand
command = null;

            var
dataContext = AssociatedObject.DataContext;

            foreach (var info
in dataContext.GetType().GetProperties(BindingFlags.Public |
BindingFlags.Instance))

            {


                if (IsCommandProperty(info) &&
String.Equals(info.Name, CommandName, StringComparison.Ordinal))

                {


                    command = (ICommand)info.GetValue(dataContext, null);

                    break;

                }


            }


            if
((command != null) &&
command.CanExecute(CommandParameter))

            {


                command.Execute(CommandParameter);

            }


        }

        private
static bool IsCommandProperty(PropertyInfo property)

        {

            return typeof(ICommand).IsAssignableFrom(property.PropertyType);


        }

        public
string CommandName

        {

            get

            {


                return (string)GetValue(CommandNameProperty);

            }


            set

            {


                SetValue(CommandNameProperty, value);

            }


        }

        public
object CommandParameter

        {

            get

            {


                return GetValue(CommandParameterProperty);

            }


            set

            {


                SetValue(CommandParameterProperty, value);

            }


        }

    }

}