Soft keyboard moves application up

Hi!

   i am now developing a game using flash builder 4.6 and air 3.3 sdk. i use TextField and the type is set TextFieldType.INPUT .

   When I click a textfield at the bottom of the screen, the soft keybord appears and my application is moved upwards in order to keep the textfield visible.

   If i set the multiline of textfield "false", when i click outside of the textfield ,or click the OK button on the soft keyboard, the keyboard disappear , and my application still stays on top, and can not move down again.

    but if i set the multiline to true, if i click outside of the textfield, the keyboard disappear ant my application goes down.

   why this happens, and how can i let the textfield down automatically with my textfield multiline set to false.

  Thanks for any reply