创建一个含有方块的面板，用户可以通过鼠标抓取方块，但是，无论用户怎样努力，方块总是朝着与鼠标运动相反的方向运动，这就是抓不住的方块。 -Create a panel containing a box, the user can grab the mouse box, but no matter how hard the user, always moving boxes moving in the opposite direction with the mouse movement, and this is the box not catch.