Windows Phone 7 MVVM模式通訊方式之實現Command

l_serein發表於2013-04-11
WindowsMVVM模式

MVVM模式的View與ViewModel的三大通訊方式：Binding Data（實現資料的傳遞）、Command（實現操作的呼叫）和Attached Behavior（實現控制元件載入過程中的操作）。

（1）MainPage.xaml檔案的程式碼,實現View層
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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">
    <!--設定整個頁面的上下文資料DataContext為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檔案的程式碼,實現ViewModel層
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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類，實現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);
            }
        }
    }
}

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