Android Studio 0.5.0 -升级后没有自动代码完成和语法错误识别

I upgraded Android Studio to 0.5.0 without any issues until I started writing code. It's so weird. Auto code completion didn't work any more. No drop-down list got showed up. Even worse, I intentionally wrote wrong syntax but the IDE failed to warn automatically as it still does at the scrolling line (on the right).I upgraded Android Studio to 0.5.0 without any