library/src/main/java/com/bumptech/glide/load/engine/Resource.java

package com.bumptech.glide.load.engine;


/**
 * A resource interface that wraps a particular type so that it can be pooled and reused.
 *
 * @param <Z> The type of resource wrapped by this class.
 */
public interface Resource<Z> {

    /**
     * Returns an instance of the wrapped resource.
     * <p>
     *     Note - This does not have to be the same instance of the wrapped resource class and in fact it is often
     *     appropriate to return a new instance for each call. For example,
     *     {@link android.graphics.drawable.Drawable Drawable}s should only be used by a single
     *     {@link android.view.View View} at a time so each call to this method for Resources that wrap
     *     {@link android.graphics.drawable.Drawable Drawable}s should always return a new
     *     {@link android.graphics.drawable.Drawable Drawable}.
     * </p>
     */
    Z get();

    /**
     * Returns the size in bytes of the wrapped resource to use to determine how much of the memory cache this resource
     * uses.
     */
    int getSize();

     /**
     * Cleans up and recycles internal resources.
     *
     * <p>
     *     It is only safe to call this method if there are no current resource consumers and if this method has not
     *     yet been called. Typically this occurs at one of two times:
     *     <ul>
     *         <li>During a resource load when the resource is transformed or transcoded before any consumer have
     *         ever had access to this resource</li>
     *         <li>After all consumers have released this resource and it has been evicted from the cache</li>
     *     </ul>
     *
     *     For most users of this class, the only time this method should ever be called is during transformations or
     *     transcoders, the framework will call this method when all consumers have released this resource and it has
     *     been evicted from the cache.
     * </p>
     */
    void recycle();
}