title: How to save images from server and reuse later
body: <p>I have an Application and that is live on google, but Now we have plan to change its little working to make it less in size. At the time now its about 60mb and its just due to number of images we have packaged in. Now We have decided to send less embed images in the app built and later let the user download these manually from the server. But I have confusion in couple of things. and these are as following. </p>
  
  <ul>
  <li>How to download the images from server and save them in the device to reuse purpose. I mean let say we have uploaded 10 images on server, user download all of them , now next time if our server has no new images the last 10 images which are saved in devices should be able to reuse and should not be download by the app again.</li>
  </ul>
  
  <p>so this point has three more point </p>
  
  <ul>
  <li>1) How to download and where to download the images </li>
  <li>2) If the user has deleted some images downloaded then how to check which images are deleted and to re download them. </li>
  <li>3) Is there any way to save the images in a place where user can not see them out side app and not be able to delete them (to eliminate my second point)</li>
  </ul>
  
  <p>Also I have an grid view I am using them to show the image in grid , user click on the image and the real images open in new activity with some info now I have confusion in this also and that is </p>
  
  <ol>
  <li>As we are planning to embed at least 10 images in apk , so we need to show them in the grid (its easy as I am showing them from the app resource folder into the grid view ). But now as we have to download the images from server also , so now How do we populate the images into that grid view and how do we keep track that which image is coming from where either from the resource (as in previous version ,I have just to get it from drawable. but now the things are changed and complicated) </li>
  </ol>
  
  <p>so in short the grid view is mix up of the local app images and the images from the server. </p>
  
  <ol start="2">
  <li>would  not it be time consuming to search the last downloaded images from the device and them to display them into a grid view ?</li>
  </ol>
  
  <p>Thanks for reading so long question.</p>