question: private void startNewTransition ( ) { if ( ! hasBounds ( ) ) { throw new UnsupportedOperationException ( "Can't start transition if the " + "drawable has no bounds!" ) ; } mCurrentTrans = mTransGen . generateNextTransition ( mDrawableRect , mViewportRect ) ; mElapsedTime = 0 ; mLastFrameTime = System . currentTimeMillis ( ) ; fireTransitionStart ( mCurrentTrans ) ; }
target:  Generates and starts a transition.