onActivityResult do not fire if launch mode of activity is singleInstance

Question

I have an Activity which is basically my main activity and its launch mode is single instance. But because of singleInstance, the onActivityResult() callback do

Answer 1

Android Source Code

Check "ActivityStarter.computeLaunchingTaskFlags()" method:

            } else if (mSourceRecord.launchMode == LAUNCH_SINGLE_INSTANCE) {
            // The original activity who is starting us is running as a single
            // instance...  this new activity it is starting must go on its
            // own task.
            mLaunchFlags |= FLAG_ACTIVITY_NEW_TASK;

That's the reason why NEW_TASK flag is added when your original activity with single instance launch mode.

More Source Code

Check "ActivityStarter.sendNewTaskResultRequestIfNeeded()" method:

        if (sourceStack != null && (mLaunchFlags & FLAG_ACTIVITY_NEW_TASK) != 0) {
        // For whatever reason this activity is being launched into a new task...
        // yet the caller has requested a result back.  Well, that is pretty messed up,
        // so instead immediately send back a cancel and let the new task continue launched
        // as normal without a dependency on its originator.
        Slog.w(TAG, "Activity is launching as a new task, so cancelling activity result.");
        sourceStack.sendActivityResultLocked(-1 /* callingUid */, mStartActivity.resultTo,
                mStartActivity.resultWho, mStartActivity.requestCode, RESULT_CANCELED,
                null /* data */);

That's the reason why FLAG_ACTIVITY_NEW_TASK always immediately return RESULT_CANCELED.