Java – How to discover the intent of another application

I’m trying to build an app to receive shares from the StumbleUpon app.
At this point, I can receive a “share URL” from my browser, but when sharing from StumbleUpon my app doesn’t appear in the list.

I

was thinking I might not have registered the correct intents in the list.
Is there any way to find out what the app is doing?

Thank you.

You can get some information about intents from logcat. I noticed this in the log when I shared it in StumbleUpon :

12-08 19:01:18.915: I/ActivityManager(139): Starting activity: Intent { act=android.intent.action.SEND typ=text/plain flg=0x3000000 cmp=com.google.android.gm/. ComposeActivityGmail (has extras) } from pid 4213

This allows me to use the following filter to have the app appear in the StumbleUpon shared list:

<intent-filter>
   <action android:name="android.intent.action.SEND" />
   <category android:name="android.intent.category.DEFAULT" />
   <data android:mimeType="text/plain"/>
</intent-filter>