Preload multiple images with Glide

Use the following code to cache images without displaying them

1. using the downloadOnly method if you are looking to download images from the web and store them in the diskCache:

   FutureTarget<File> future = Glide.with(applicationContext)
       .load(yourUrl)
       .downloadOnly(500, 500);
   

2. using preload method if you want to load them into the Memory Cache.

   Glide.with(context)
           .load(url)
           .preload(500, 500);
   

You can later use the cached images using

Glide.with(yourFragment)
    .load(yourUrl)
    .into(yourView);

---

The best option is to handle caching yourself, it gives you more control & should be easy as you already know what bitmaps are to be loaded.

First: Setup a LruCache

LruCache<String, Bitmap> memCache = new LruCache<>(size) {
    @Override
    protected int sizeOf(String key, Bitmap image) {
        return image.getByteCount()/1024;
    }
};

Second: Load the bitmaps to the LruCache

Display display = getWindowManager().getDefaultDisplay();
Point size = new Point();
display.getSize(size);
int width = size.x; //width of screen in pixels
int height = size.y;//height of screen in pixels
Glide.with(context)
    .load(Uri.parse("file:///android_asset/imagefile"))
    .asBitmap()
    .fitCenter() //fits given dimensions maintaining ratio
    .into(new SimpleTarget(width,height) {
        // the constructor SimpleTarget() without (width, height) can also be used.
        // as suggested by, An-droid in the comments
        @Override
        public void onResourceReady(Bitmap resource, GlideAnimation glideAnimation) {
            memCache.put("imagefile", resource);
        }
    });

Third: Use the cached bitmaps

Bitmap image = memCache.get("imagefile");
if (image != null) {
    //Bitmap exists in cache.
    imageView.setImageBitmap(image); 
} else {
    //Bitmap not found in cache reload it 
    Glide.with(context)
         .load(Uri.parse("file:///android_asset/imagefile"))
         .into(imageView);
}