如何在Preference屏幕中使用数据输入？ （android蜂窝）

In my app, I have used the two-pane preference screen as given in the API Demo. Now, in edit text preference, I have an option to login into Picasa. After the user inputs his username and password, how do I link that data to my activity? How can I get that data and write it in the preference file? In my app, I have used the two-pane preference