Lollipop: making my activity stay in the task that

问题:

“My First App” has an activity that handles a “share” intent. Its activity in AndroidManifest.xml looks like this:

    <activity
        android:name="com.example.foo.myfirstapp.MainActivity"
        android:label="@string/app_name">
        <intent-filter>
          <action android:name="android.intent.action.SEND"/>
          <category android:name="android.intent.category.DEFAULT"/>
          <data android:mimeType="image/jpeg"/>
        </intent-filter>

    </activity>

In KitKat, sharing an image from the album to “My First App” causes MainActivity to be part of the album’s task. This is the desired behavior.

In Lollipop, sharing an image from the album to “My First App” causes a new instance of “My First App” to be launched. If I look at the overview screen, the album task is there...and then there's a separate entry for "My First App". If I share another image, I wind up with two instances of "My First App"...etc.

Question: How do I make Lollipop process the share intent in the same way as KitKat?

Here's what I've done: I notice that the intents sent from the Album have different flags set depending on the OS. (I got these using getIntent() and looking at mFlags.)

Kitkat: 0x80001 (524289): FLAG_GRANT_READ_URI_PERMISSION, FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET

Lollipop: 0x18080001 (403177473): FLAG_GRANT_READ_URI_PERMISSION, FLAG_ACTIVITY_MULTIPLE_TASK, FLAG_ACTIVITY_NEW_DOCUMENT, FLAG_ACTIVITY_NEW_TASK

From reading http://developer.android.com/reference/android/content/Intent.html, it seems that these last three flags are causing the problem. Specifically

When paired with FLAG_ACTIVITY_MULTIPLE_TASK both of these behaviors (FLAG_ACTIVITY_NEW_DOCUMENT or FLAG_ACTIVITY_NEW_TASK) are modified to skip the search for a matching task and unconditionally start a new task.

I’ve been attempting to “override” these flags by specifying android:launchMode and android:documentLaunchMode in the activity in AndroidManifest.xml without success.

From http://developer.android.com/reference/android/R.attr.html#documentLaunchMode, using documentLaunchMode “never” seems promising, since

This activity will not be launched into a new document even if the Intent contains Intent.FLAG_ACTIVITY_NEW_DOCUMENT. This gives the activity writer ultimate control over how their activity is used. but this didn't work.

I also considered android:taskAffinity, but there doesn’t seem to be a way to say “please prefer whatever task launched you”.

回答1:

Afraid you can't do anything about this. It isn't under your control. This is a change in the way the "Album" app is launching its "share" Intent. If it doesn't want your Activity in its task, you can't force it in there.

If you have issues with having multiple instances of your "share" activity, you could declare your "share" activity as launchMode="singleTask" or launchMode="singleInstance" (depending on your needs. This may, however, break other things.