android screenshot problem

Ask you a question, when achieved with android screenshot, screenshot I found that sometimes the picture is normal, and sometimes actually did not produce a screenshot pictures, or pictures too less than 1k, ask someone you met before? Oh, how to solve?

Screenshot code used here
http://www.2cto.com/kf/201208/146876.html <-! Main posts under Banner (D4) -><-! Posts under the main text (D5) ->
Reply:
You figure this intercept is the application layer, should be no problem, is not without emptying device data