WPF MVVMToolkit框架學習-ObservableRecipient

ObservableRecipient 就是用來在VM之間相互傳值的

比ObservableObject多了一個屬性 IsActive（用來激活VM，使它能夠接受到消息） 和一個Messenger 用來注冊和發送消息

有兩種機制可以使用 

第一種繼承 ObservableRecipient  

后台代碼

using Microsoft.Toolkit.Mvvm.ComponentModel;
using Microsoft.Toolkit.Mvvm.Input;
using Microsoft.Toolkit.Mvvm.Messaging;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Input;

namespace MVVMToolkit框架學習
{
    public class SendVM : ObservableObject
    {
        private string _showMsg;

        public string ShowMsg
        {
            get => _showMsg;
            set => SetProperty(ref _showMsg, value);
        }

        public ICommand SendCmd { get; set; }

        public SendVM()
        {
            SendCmd = new RelayCommand(() =>
            {
                //如果沒有繼承至ObservableRecipient，使用WeakReferenceMessenger發送和注冊消息
                WeakReferenceMessenger.Default.Send(this);
            });
        }
    }
}

using Microsoft.Toolkit.Mvvm.ComponentModel;
using Microsoft.Toolkit.Mvvm.Messaging;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MVVMToolkit框架學習
{
    public class RecipientA1VM : ObservableRecipient
    {
        private string _displayMsg = "我是接收者";

        public string DisplayMsg
        {
            get => _displayMsg;
            set => SetProperty(ref _displayMsg, value);
        }

        public RecipientA1VM()
        {
            //VM需要是激活的才能接受到消息
            IsActive = true;
        }

        protected override void OnActivated()
        {
            //注冊消息，有多個重載方法，按需使用 如果使用多個相同類型注冊，可以使用Token來進行區分
            Messenger.Register<RecipientA1VM, SendVM>(this, (r, s) => r.Receive(s));
        }

        private void Receive(SendVM msg)
        {
            //對收到的消息處理
            DisplayMsg = "接收到了" + msg.GetType().Name + "的消息:" + msg.ShowMsg;
        }
    }
}

界面代碼

<Window
    x:Class="MVVMToolkit框架學習.SendView"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:local="clr-namespace:MVVMToolkit框架學習"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    Title="SendView"
    Width="800"
    Height="450"
    d:DataContext="{d:DesignInstance Type={x:Type local:SendVM}}"

    mc:Ignorable="d">
    <Window.DataContext>
        <local:SendVM />
    </Window.DataContext>
    <Grid>
        <StackPanel
            MinWidth="200"
            HorizontalAlignment="Center"
            VerticalAlignment="Center"
            Orientation="Vertical">
            <Button Click="OpenRecipientView" Content="打開接受窗口" />

            <StackPanel Orientation="Horizontal">
                <TextBlock Text="要發送的消息:" />
                <TextBox MinWidth="150" Text="{Binding ShowMsg}" />
            </StackPanel>
            <Button Command="{Binding SendCmd}" Content="發送消息" />
        </StackPanel>
    </Grid>
</Window>

<Window
    x:Class="MVVMToolkit框架學習.RecipientView"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:local="clr-namespace:MVVMToolkit框架學習"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    Title="RecipientView"
    Width="800"
    Height="450"
    d:DataContext="{d:DesignInstance Type={x:Type local:RecipientA1VM}}"
    mc:Ignorable="d">
    <Window.DataContext>
        <local:RecipientA1VM />
    </Window.DataContext>
    <Grid>
        <TextBlock
            MinWidth="75"
            HorizontalAlignment="Center"
            VerticalAlignment="Center"
            FontSize="30"
            Text="{Binding DisplayMsg}" />
    </Grid>
</Window>

另外一種是繼承IRecipient<T>接口，同樣也能實現同樣的目的

 接受VM的代碼

using Microsoft.Toolkit.Mvvm.ComponentModel;
using Microsoft.Toolkit.Mvvm.Messaging;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MVVMToolkit框架學習
{
    public class RecipientA2VM : ObservableObject, IRecipient<string>
    {
        private string _displayMsg = "我是接收者";

        public string DisplayMsg
        {
            get => _displayMsg;
            set => SetProperty(ref _displayMsg, value);
        }

        public RecipientA2VM()
        {
            WeakReferenceMessenger.Default.Register(this);
        }

        public void Receive(string message)
        {
            DisplayMsg = message;
        }
    }
}