android: how do i open another app from my app?

I understand how to use intents and startActivity() when opening another activity within my own app, but how do you start a different app? specifically:

• How do you determine if the user has the needed app installed on their device?
• How do you start that app?
• How do you pass parameters to that app?
• How do you find all this info out for a specific app (say Adobe reader, or google maps)?

How to see if Intent is available:

1. Try calling Intent and deal with ActivityNotFoundException if it isn't available

   Intent intent = new Intent(Intent.ACTION_VIEW);
   intent.setDataAndType(path, "application/pdf");
   intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
   
   try {
       startActivity(intent);
   } 
   catch (ActivityNotFoundException e) {
       Toast.makeText(OpenPdf.this, 
           "No Application Available to View PDF", 
           Toast.LENGTH_SHORT).show();
   }
   

   or

2. Query the Package Manager to see if it is ahead of time:

   PackageManager packageManager = getPackageManager();
   Intent intent = new Intent(Intent.ACTION_VIEW);
   intent.setType("application/pdf");
   
   List list = packageManager.queryIntentActivities(intent,
       PackageManager.MATCH_DEFAULT_ONLY);
   
   if (list.size() > 0) {
       intent.setDataAndType(path, "application/pdf");
       startActivity(intent);
   }
   

How to pass parameters to an application or know its capabilities:

1. List of Available Intents for Google Applications
2. List of Intents by 3rd parties @ OpenIntents

What you are looking for are intents and intent filters.

Everything you want to know is detailed on the Android developer guide.

http://developer.android.com/guide/topics/intents/intents-filters.html