onActivityResult being called instantly

Question

I'm launching an activity using startActivityForResult() from a button handler, and my onActivityResult() is being called instantly, even before the onCreate() for the target activity is being hit.

public void onGraphNext (View target) {
    Intent i = new Intent(this, AddCommentActivity.class);
    startActivityForResult(i,6);    // 6 is arbitrary request code               
}    

. . .

protected void onActivityResult(int requestCode, int resultCode,
        Intent returnData) {
   if  ( (resultCode == RESULT_OK) && (requestCode == 6) ) {
   Bundle extras = returnData.getExtras();
   comment = extras.getString("comment");
     }
} 

The result code returned is 0 and the request code is 6. Elsewhere on StackOverflow I've seen people report this problem and the solution was to not use singeInstance for the launchMode in the manifest. But I'm using standard . . .

<activity android:name="AddCommentActivity"
          android:configChanges="orientation"
          android:screenOrientation="portrait"
          android:launchMode="standard"></activity>  

Thanks in advance for any insights!

EDIT: I made a simple test program and I can reproduce the problem reliably when the caller ("launcher") - the activity with the onActivityResult - is a singleInstance and the Activity being invoked ("launchee") is standard. i.e.,

<activity android:name="Launcher"
          android:screenOrientation="portrait"
          android:launchMode="singleInstance"></activity> 

<activity android:name="Launchee"
          android:screenOrientation="portrait"
          android:launchMode="standard"></activity>  

This is a problem for me because in the real app, the called must be a singleInstance for other reasons, but it wants to have buttons to start up other activities to request user input. How else to do this if I can't use startActivityForResult?

Answer 1

You cannot use startActivityForResult() if the activity being started is not running in the same task as the activity that starts it. This means that neither of the activities can have launchMode="singleInstance". If you require that these 2 activities run in different tasks, then you need to use a different mechanism. The documentation for startActivityForResult() sorta-kinda hints at this:

"For example, if the activity you are launching uses the singleTask launch mode, it will not run in your task and thus you will immediately receive a cancel result."

What you can do is to simply start the activity using startActivity() and have the called activity call startActivity() to return to your activity, sending back data as necessary as extras in the Intent it uses.

However, you might consider whether you really need these special launchModes. In general they are only necessary for HOME-screen replacements and other very special applications. Most developers who use singleInstance or singleTask launch modes are using them incorrectly.