如何在单击取消按钮上的日期选择器对话框时完成活动

I have implemented the date picker dialog on my activity and it works fine. When i click cancel the ate picker is dismissed so the buttons work. However i would like to capture the cancel button event and add more code to it to finish the activity but i cannot seem to be able to handle that. This is my code:I have implemented the date picker dialog on my