Rotate an Imagewith Animation

If I were you I'd use ViewPropertyAnimator (available from API 12). Its syntax is more straight forward IMO.
Usage would be:

toggle.animate().rotation(0.5f);

First of all, what is you minimum SDK requirement? In case it's at least Android 3.0, you can use the newer animation framework, and animate your Image with something like this:

imageView.animate().rotation(180).start();

About the flicker: I wouldn't reset the source image of the ImageView after the rotation, I'd just leave in the original and make sure that the rotation animation fills after the animation, leaving the image rotated. The flicker is most likely caused by the View's relayout/redraw upon changing the source image.

Further visual artifacts (flicker?) may be caused because the original-rotated image and the rotated static image might differ in a few pixels.