question: private void pullEvent ( ) { final int newScrollValue ; final int itemDimension ; final float initialMotionValue , lastMotionValue ; switch ( getPullToRefreshScrollDirection ( ) ) { case HORIZONTAL : initialMotionValue = mInitialMotionX ; lastMotionValue = mLastMotionX ; break ; case VERTICAL : default : initialMotionValue = mInitialMotionY ; lastMotionValue = mLastMotionY ; break ; } switch ( mCurrentMode ) { case PULL_FROM_END : newScrollValue = Math . round ( Math . max ( initialMotionValue - lastMotionValue , 0 ) / FRICTION ) ; itemDimension = getFooterSize ( ) ; break ; case PULL_FROM_START : default : newScrollValue = Math . round ( Math . min ( initialMotionValue - lastMotionValue , 0 ) / FRICTION ) ; itemDimension = getHeaderSize ( ) ; break ; } setHeaderScroll ( newScrollValue ) ; if ( newScrollValue != 0 && ! isRefreshing ( ) ) { float scale = Math . abs ( newScrollValue ) / ( float ) itemDimension ; switch ( mCurrentMode ) { case PULL_FROM_END : mFooterLayout . onPull ( scale ) ; break ; case PULL_FROM_START : default : mHeaderLayout . onPull ( scale ) ; break ; } if ( mState != State . PULL_TO_REFRESH && itemDimension >= Math . abs ( newScrollValue ) ) { setState ( State . PULL_TO_REFRESH ) ; } else if ( mState == State . PULL_TO_REFRESH && itemDimension < Math . abs ( newScrollValue ) ) { setState ( State . RELEASE_TO_REFRESH ) ; } } }
target:  Actions a Pull Event