Pre cache Image Media Source

I am not sure if these functions provide that what I am looking for. The *MediaPlayer *loads a source and starts with caching. I need to know when caching is done.
Like in the image below (which shows the time bar of the MediaPlayer): If I load a image source, the green line starts to fill the time bar. I need to know when the bar it is fully green. In other words, if caching is in progress or not.

I tested with the blueprint functions is Buffering and is Preparing. Seems both do not tell if caching is in progress.

Any idea how to get the state of the caching progress?