防止XAML图像的本地副本

Question

我在XAML中设置了两个图像元素的来源.如何使它们指向同一个对象,这样如果其中一个图像的源更改,则第二个图像会自动更改.目前,通过设置XAML图像的源,它们都保持自己的本地副本.例如,我有两个图像元素

<Image x:Name="abc" /> and <Image x:name="def"/>

我设置了abc.Source ="xyz"和def.Source ="xyz".现在两个(abc和def)都有自己的图像副本"xyz".如何让它们指向同一个图像对象.因此没有必要保留2份"xyz".

Answer 1

我不太确定我是否理解正确.我想你可能希望能够一次更改ImageSource并自动更新两个图像,而不是在每次更改时明确设置每张图片的Source.这将是绑定的描述.

这是该案例的实现:

视图模型:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Windows.Input;
namespace WpfApplication1
{
    public class MyViewModel : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        protected void OnPropertyChanged(string propertyName)
        {
            if (this.PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }

        private string _source;
        public string Source { get { return _source; } set { _source = value; OnPropertyChanged("Source"); } }

        public ICommand ChangeImageCommand { get; private set; }

        private List<string> _pics = new List<string>()
        {
            "/Themes/Evernote.png",
            "/Themes/Skype.png", 
            "/Themes/Twitter.png"
        };

        private int i = 0;

        public MyViewModel()
        {
            this.Source = _pics[i++];
            this.ChangeImageCommand = new ActionCommand(ChangeImage);
        }

        private void ChangeImage()
        {
            this.Source = _pics[i++ % _pics.Count];
        }
    }

    public class ActionCommand : ICommand
    {
        public event EventHandler CanExecuteChanged;
        private Action _action;
        public ActionCommand(Action action) { _action = action; }
        public bool CanExecute(object parameter) { return true; }
        public void Execute(object parameter) { if (_action != null) _action(); }
    }
}

XAML:

<Window x:Class="WpfApplication1.MainWindow"
            xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
            xmlns:local="clr-namespace:WpfApplication1"            
            Title="MainWindow" Height="350" Width="500">

    <Window.DataContext>
        <local:MyViewModel />
    </Window.DataContext>
    <StackPanel Background="Maroon">
        <Image x:Name="Image1" Source="{Binding Source}" Margin="20" Width="100" />
        <Image x:Name="Image2" Source="{Binding Source}" Margin="20" Width="100" />
        <Button Command="{Binding ChangeImageCommand}" Content="Change Image" HorizontalAlignment="Center" />
    </StackPanel>
</Window>