问题
I am calling the ZXing scanner from Screen-A using Intents. Once the scan is done, control returns, of course, to the code behind Screen-A and I do some other work before calling Screen-B.
Problem is: the screen is black during this work period and I cannot determine the proper context to use to display a "working..." Toast/msgbox. Any help or suggestions?
回答1:
Execute your "work period" in it's own thread, while that thread works in the background Android will pass control to Screen-A which will can display a ProgressBar. The "work period" thread will pass Messages to Screen-A updating the value of a variable that measures progress. Here's a good place to start with Android threads:
http://developer.android.com/guide/appendix/faq/commontasks.html#threading
回答2:
Can't you display a ProgressDialog before your call to ZXing and then dismiss it in onActivityResult() ?
来源：https://stackoverflow.com/questions/774545/android-determining-the-current-context-to-display-an-alert