code: public void restart() {
          int width = getWidth();
          int height = getHeight();
  
          if (width == 0 || height == 0) {
              return; // Can't call restart() when view area is zero.
          }
  
          updateViewport(width, height);
          updateDrawableBounds();
  
          startNewTransition();
      }
docs: Creates a new transition and starts over.