title: Creating a default viewer / receiver for Android email attachments
body: <p>I'm trying to create a default handler for .p7s/.p7b files in Android.</p>
  
  <p>I figured the best start would be to create a BroadcastReceiver that will capture the intent from the Android email application (or K-9 if that's a need) for opening of certain attachments (filtered by mime type). Specifically I'm trying to handle s/mime email so looking for the "application/x-pkcs7-certificates" and "application/x-pkcs7-certificates" mime types.</p>
  
  <p>Just as a basic test I've been trying something like this:</p>
  
  <p>Manifest.xml</p>
  
  <pre><code>&lt;receiver android:name=".IntentReceiver" android:enabled="true"&gt;
       &lt;intent-filter&gt;
              &lt;action android:name="android.intent.action.VIEW" /&gt;
              &lt;category android:name="android.intent.category.DEFAULT" /&gt;
              &lt;category android:name="android.intent.category.BROWSABLE" /&gt;
              &lt;data android:mimeType="application/x-pki-signature"/&gt;
       &lt;/intent-filter&gt;
  &lt;/receiver&gt;
  </code></pre>
  
  <p>Class file.</p>
  
  <pre><code>public class IntentReceiver extends BroadcastReceiver {
      @Override
      public void onReceive(Context context, Intent intent) {
          Log.d("TEST", "Intent was caught");
          //Do something here
      }
  }
  </code></pre>
  
  <p>I've tried using the following mimeType filters as well (testing signatures first):</p>
  
  <pre><code>application/pkcs7-signature
  application/x-pkcs7-signature
  application/keychain_access
  </code></pre>
  
  <p>I can't seem to get the IntentReceiver class to capture the intent no matter what filtering I use though. Am I going about this the wrong way?</p>