c# - 在 Xamarin Forms 中获取缓存图像源的原始高度和宽度

Question

除了按如下方式检查加载是否成功之外，还有其他方法可以访问 CachedImage 的 ImageInformation 中的 OriginalHeight 和 OriginalWidth 吗？

CachedImage img = new CachedImage() 
{ 
    CacheType = FFImageLoading.Cache.CacheType.Memory 
};
img.Source = GetNextImage();
img.Success += (sender, e) =>
{
    h = e.ImageInformation.OriginalHeight;
    w = e.ImageInformation.OriginalWidth;

    if (Device.Idiom == TargetIdiom.Phone)
    {
        if (h > w)
        {
            img.HeightRequest = 400;
        }
    }
    if (Device.Idiom == TargetIdiom.Tablet)
    {
        if (h > w)
        {
            img.HeightRequest = 800;
        }
     }            
 };

Answer 1

使用 FFImageLoading 库，你的方法是正确的 w/Success，但是如果你的 Resource 文件夹下有图像，也许可以使用下面的方法/想法:

PLC/标准:

using Xamarin.Forms;

namespace YourProject.Utils
{
    public interface IImageResource
    {
        Size GetSize(string fileName);
    }
}

安卓:

using Android.Graphics;
using YourProject.Droid.Utils;
using YourProject.Utils;
using System;
using Xamarin.Forms;

[assembly: Dependency(typeof(ImageResource))]
namespace YourProject.Droid.Utils
{
    public class ImageResource : Java.Lang.Object, IImageResource
    {
        public Size GetSize(string fileName)
        {
            var options = new BitmapFactory.Options
            {
                InJustDecodeBounds = true
            };

            fileName = fileName.Replace('-', '_').Replace(".png", "").Replace(".jpg", "");
            var resId = Forms.Context.Resources.GetIdentifier(fileName, "drawable", Forms.Context.PackageName);
            BitmapFactory.DecodeResource(Forms.Context.Resources, resId, options);

            return new Size((double)options.OutWidth, (double)options.OutHeight);
        }
    }
}

iOS:

using YourProject.iOS.Utils;
using YourProject.Utils;
using System;
using UIKit;
using Xamarin.Forms;

[assembly: Dependency(typeof(ImageResource))]
namespace YourProject.iOS.Utils
{
    public class ImageResource : IImageResource
    {
        public Size GetSize(string fileName)
        {
            UIImage image = UIImage.FromFile(fileName);
            return new Size((double)image.Size.Width, (double)image.Size.Height);
        }
    }
}

使用 Xamarin.Forms.DependencyService:

var imageSize = DependencyService.Get<IImageResource>().GetSize("ic_launcher.png");
System.Diagnostics.Debug.WriteLine(imageSize);

通过 XAML 的另一个选项:

<ContentView.Resources>
    <ResourceDictionary>
        <Style x:Key="CachedImageStyle" TargetType="{x:Type ffimageloading:CachedImage}">
           <Setter Property="HorizontalOptions" Value="Center" />
           <Setter Property="VerticalOptions" Value="Center" />
           <Setter Property="HeightRequest">
             <Setter.Value>
               <OnIdiom x:TypeArguments="x:Double" Tablet="800" Phone="400" />
             </Setter.Value>
           </Setter>
         </Style>
    </ResourceDictionary>
</ContentView.Resources>

<ContentView.Content>
    <!-- ... -->
    <ffimageloading:CachedImage
        x:Name="cachedImg"
        Style="{StaticResource CachedImageStyle}">
      </ffimageloading:CachedImage>
    <!-- ... -->
</ContentView.Content>

然后，您可以创建一个转换器来设置平板电脑/手机的尺寸，也许可行。

希望对您有所帮助。