android-widget-task-issue

The problem

When launching a startActivityForResult or ActivityCallback.StartActivityForResult from an activity that was launched by a widget configuration activity, the task management is not the same as when launched from a regular activity.

Forewords

I discovered this issue while working with widgets.

Users of these widgets must authenticate through an OAuth flow as part of the configuration process.

Everything was fine while I was opening the widget's configuration activity from a call to PendingIntent.getActivity(...).

Then I've been trying to implement the widget configuration mechanism, where the configuration activity is launched by the system, and from what I understand, a different task / process.

(This is done by the framework method com.android.server.appwidget.AppWidgetServiceImpl.createAppWidgetConfigIntentSender)

That's where the trouble began: If launched from the system, the activities task management does not work the same as from my own task / app process.

I've reproduced schematically the OAuth / Activity flow in a sandbox that you can check out in this github repository.

And here is some ASCII art to illustrate this flow:

                          Back Stack Towards Top
                +------------------------------------------>

 +------------+            +---------------+            +----------------+     
 |            |     (1)    |               |     (2)    |                | 
 | Widget     +----------->|    OAuth      +----------->| OAuthCallback  +
 | Config     |            |    Activity   |            |   Activity     |
 | Activity   |<-----------+               |<-----------+                |
 |  (SI)      |     (4)    |      (ST)     |     (3)    |     (SI)       | 
 +------------+            +-+---+---------+            +----------------+

Legend:
(1): startActivityForResult to `OAuthActivity`
(2): startActivity to `OAuthCallBackActivity`
(3): startActivity with flags: CLEAR_TOP | SINGLE_TOP to `OAuthActivity`
(4): finish() (with setResult(OK/CANCEL)
(SI): launchMode="singleInstance"
(ST): launchMode="singleTask"

Steps to reproduce:

Step 1

Clone this sandbox: https://github.com/Datadog/android-widget-task-issue

Step 2

Build & Install the application WidgetTaskIssue

Android 12

Step 3

Open your widget picker for the WidgetTaskIssue application, and set up the widget named Widget on your home screen.

Step 4

• Tap Open configuration button on the widget.
• Tap Start OAuth button
• Tap Get callback button

In your logcat, filter by System.out, you should see the proper output

Step 5

Long press your widget and tap the configuration icon (The little pen) or use drag & drop to configure.

• Tap Start OAuth button
• Tap Get callback button

In your logcat, filter by System.out, you should see the faulty output

<= Android 11

Step 3

Open your widget picker for the WidgetTaskIssue application, and set up the widget named Widget on your home screen.

Step 4

The configuration activity should open automatically.

• Tap Start OAuth button
• Tap Get callback button
• Tap the close button to close the activity

In your logcat, filter by System.out, you should see the faulty output

Step 5

Now that you have a widget installed and configured.

• Tap Open configuration button on the widget.
• Tap Start OAuth button
• Tap Get callback button

In your logcat, filter by System.out, you should see the proper output

Tested on

• Pixel 4 / Android 12
• Pixel 3a / Android 12
• Xiaomi 10 / Android 11

Why it is problematic

Whether my activity is launched from my app process vs a background service process, the task management should remain identical, otherwise I can't trust the Android documentation about activities and launch flags.

It also breaks any OAuth implementing the aforementioned activity flow, which relies on previously created activity resuming through onNewIntent / onResume, instead of a new activity being recreated in a different task.

What the correct behavior should be

When I use startActivityForResult from a background service such as the widget configuration mechanism, or from any other method, I should always get the same task management than if I launch from an app process, which is the one described in the proper output.

Additional question

• startActivity produces the expected task management, while startActivityForResult does not. Why is that ?
• Is there any workaround in the meantime ? Ideally one that would allow to keep the startActivityForResult call.

Appendix

Faulty logcat output

com.qlitzler.sandbox I/System.out: [Configuration]: A
com.qlitzler.sandbox I/System.out: [Oauth] Create: A
com.qlitzler.sandbox I/System.out: [Oauth] Resume: A
com.qlitzler.sandbox I/System.out: [Callback]: B
com.qlitzler.sandbox I/System.out: [Oauth] Create: C
com.qlitzler.sandbox I/System.out: [Oauth] Resume: C
com.qlitzler.sandbox I/System.out: [Oauth] Resume: A

A, B, C and D are integers representing an activity.taskId. In this case, several OAuth activity exists, and it runs in two different taskIds: A and C.

Proper logcat output

com.qlitzler.sandbox I/System.out: [Configuration]: X
com.qlitzler.sandbox I/System.out: [Oauth] Create: X
com.qlitzler.sandbox I/System.out: [Oauth] Resume: X
com.qlitzler.sandbox I/System.out: [Callback]: Y
com.qlitzler.sandbox I/System.out: [Oauth] Resume: X

X and Y are integers representing an activity.taskId. In this case, a single OAuth activity exists, and it runs in the same taskId.