WPF图像控制中的初始图像 [英] initial image in WPF Image Control

问题描述

我有一个WPF图像控件在我的项目中加载从互联网（懒加载），我想要显示初始图像在图像控制，直到主图像加载。 plz帮助我

 < DataTemplate DataType ={x：Type local：MyData}> 
 ... 
< Image Width =50Height =50Source ={Binding Path = profile_image_url_https，FallbackValue = profile_image_url_https}Horizo​​ntalAlignment =Left> 
 ... 
< / DataTemplate> 
  

解决方案

您可能可以使用 TargetNullValue 绑定，只有在加载时才设置image属性。

例如

 < BitmapImage x：Key =DefaultImageUriSource =Images / Error.ico/> 
  

 < Image Source = {Binding TestBitmapImage，
 TargetNullValue = {StaticResource DefaultImage}}/> 
  

  private BitmapImage _TestBitmapImage = null ; 
 public BitmapImage TestBitmapImage 
 {
 get {return _TestBitmapImage; 
 set 
 {
 if（_TestBitmapImage！= value）
 {
 _TestBitmapImage = value; 
 PropertyChanged.Notify（（）=> this.TestBitmapImage）; 
} 
} 
} 
  

  private void Button_Click（object sender，RoutedEventArgs e）
 {
 var img = new BitmapImage（）; 
 img.DownloadCompleted + =（s，dcea）=> 
 {
 TestBitmapImage = img; 
}; 
 img.BeginInit（）; 
 img.UriSource = new Uri（http://www.gravatar.com/avatar/c35af79e54306caedad37141f13de30c?s=128&d=identicon&r=PG）; 
 img.EndInit（）; 
} 
  

I have a WPF Image Control in my project that loads from internet (lazy loading), i want to show a initial image in Image Control until main image load. plz help me

<DataTemplate DataType="{x:Type local:MyData}">
...
 <Image Width="50" Height="50" Source="{Binding Path=profile_image_url_https, FallbackValue=profile_image_url_https}"  HorizontalAlignment="Left">
...
</DataTemplate>

解决方案

You might be able to make it work using TargetNullValue on the binding, only set the image property when it is loaded.

e.g.

<BitmapImage x:Key="DefaultImage" UriSource="Images/Error.ico" />

<Image Source="{Binding TestBitmapImage,
                        TargetNullValue={StaticResource DefaultImage}}" />

private BitmapImage _TestBitmapImage = null;
public BitmapImage TestBitmapImage
{
    get { return _TestBitmapImage; }
    set
    {
        if (_TestBitmapImage != value)
        {
            _TestBitmapImage = value;
            PropertyChanged.Notify(() => this.TestBitmapImage);
        }
    }
}

private void Button_Click(object sender, RoutedEventArgs e)
{
    var img = new BitmapImage();
    img.DownloadCompleted += (s, dcea) =>
        {
            TestBitmapImage = img;
        };
    img.BeginInit();
    img.UriSource = new Uri("http://www.gravatar.com/avatar/c35af79e54306caedad37141f13de30c?s=128&d=identicon&r=PG");
    img.EndInit();
}

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