How to open a native PDF file in Android using AIR?

Hello.I have created a flex mobile project to open and show a native PDF file in Android. I have tried three different methods below , but  I failed.

1. I created a stagewebview and used "stageWebView.loadURL". I can see the PDF View in emulator but it didn't work in Android Pad (SAMSUNG Galaxy Tab 10.1). It showed blank screen.

Note that I have installed AIR 3.3.

stageWebView1.loadURL(new File(new File("app:/assets/ZUGH-2P.pdf").nativePath).url);

2. I created a stagewebview and used stagewebview to load javascript. The javascript could run in emulator, but it didn't work in Android Pad. I failed again.

stageWebView1.loadURL(new File(new File("app:/assets/JavaScripthtml.html").nativePath).url);

3.  I imported stagewebviewbridge, which is the extended version of stagewebviewbridge. I created a stagewebviewbridge , but it could not run in emulator. I failed again.

stageWebViewbridge1.loadLocalURL( "appfile:/assets/pdf.html");

could any one give me some suggestions? Many thanks.