1.int ...pointToPosition(int x, int y)：将坐标映射成list位置序号!!    2014.08.08

Maps a point to a position in the list.

Parameters:

x X in local coordinate

y Y in local coordinate

Returns:

The position of the item which contains the specified point, or

INVALID_POSITION if the point does not intersect an item.

2.int ...getFirstVisiblePosition()：得到屏幕上list第一个可见的item  2014.08.08

Returns the position within the adapter's data set for the first item displayed on screen.

Returns:

The position within the adapter's data set