Preload multiple images with Glide

We are trying to preload images into cache memory to load them later (the images are located in the Asset folder of the application)

What we tried:

Glide.with(this)
    .load(pictureUri)
    .diskCacheStrategy(DiskCacheStrategy.ALL);

Glide.with(this)
    .load(picture_uri)
    .diskCacheStrategy(DiskCacheStrategy.ALL)
    .preload();

The issue: Images are cached only when we are trying to load/display them: They have to be loaded in memory before so that they appear faster.

Glide.with(this)
    .load(picture_uri)
    .into(imageView);

We also tried to use a GlideModule to increase the CacheMemory size:

public class GlideModule implements com.bumptech.glide.module.GlideModule {
    @Override
    public void applyOptions(Context context, GlideBuilder
        builder.setMemoryCache(new LruResourceCache(100000));
    }

    @Override
    public void registerComponents(Context context, Glide glide) {
    }
}

In the manifest:

 <meta-data android:name=".GlideModule" android:value="GlideModule"/>

Nothing is working so far. Any idea?

---

We trying to use an invisible 1 dp imageView, but the result is the same:

for(Drawing drawing: getDrawingsForTab(tab)){

    Glide.with(this)
            .load(drawing.getImage().toUri())
            .dontAnimate()
            .diskCacheStrategy(DiskCacheStrategy.ALL)
            .into(mPreloadCacheIv);

    for(Picture picture : getPictures()){

        Glide.with(this)
                .load(picture.getPicture().toUri())
                .dontAnimate()
                .diskCacheStrategy(DiskCacheStrategy.ALL)
                .into(mPreloadCacheIv);
    }
}

Answer

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);
}