title: MVVMCross Downloadcache - ProgressView during loading
body: <p>I'm currently testing the downloadcache and this really looks great.</p>
  
  <p>I have some questions regarding this plugin (I'm pretty new to C# and don't understand the full source code of the plugin):</p>
  
  <p><strong>1) ProgressView</strong> </p>
  
  <p>I would like to show a progressview on the image until it has been loaded.
  To do that, I need to be notified when the image is loaded. </p>
  
  <p>In the "MvxImageViewLoader" I see there is an Action "afterImageChangeAction" (null by default).
  However, I don't understand if and how I can access that Action from "MvxImageView"?
  (how to set it)</p>
  
  <p><strong>2) Don't load old image</strong></p>
  
  <p>When using Tables or Cellectionviews in iOS, it's important to check if the URL has been changed before setting the image (because iOS reuses the objects). I looked at the source code of the downloadcache and I don't see this check. </p>
  
  <p>However, in the "MvxDynamicImageHelper.cs" class, I see that when a new URL is set, it calls "ClearCurrentHttpImageRequest();" which removes the "update" Events.</p>
  
  <p>So I assume this is enough to prevent that an image is set to the wrong UIImageView?</p>
  
  <p><strong>3) ImageCache size in (mega)bytes</strong></p>
  
  <p>The ImageCache does not have a property to define the mamiximum size (megabytes for example) of the persistent image store (on the HD). I prefer to use a maximum size in (mega)bytes instead of a maximum amount of files because the user will care more how much space an app takes instead of how many files are stored by the app.</p>
  
  <p>I assume the easiest for me is to define a "TimeSpan PeriodSaveInterval" independent from the one in MvxFileDownloadCache to just check the size of the folder defined for the Image Cache or any other recommendations?</p>
  
  <p>Is it dangerous for performance to scan the folder and calculate the size of all the images in a folder?</p>
  
  <p>Regards,
  Matt</p>