Please help me! i can't get correct mouse position when touch screen

first, forgive my bad english, this is the issue:when button press event called, i get mouse position from playercontroller by mouse click is correct, but when i touch the button(still called button press) on our device which have touch screen, i got mouse position that is last time mouse hovered before i touch, the position update until touch over, looks like mouse was captured when touch,i don’t know what happed! please help me figure it out, it’s drive me crazy. hope i make my question clear.=)