Force instrumented activity run in multi-window mode

Issue

As you know, android provided Multi-Window support mode in android N. Our application has multi-window support.
But how to test it? How to force test run the app in that mode? I haven't founded any such method in Instrumentation class or anywhere else in documentation. Maybe it is somehow possible with Espresso?

Solution

Unfortunately the way provided by azizbekian requires an app which has been loaded in multi-window mode previously, so I want to provide own solution. At the answer I have found how to enter multi-window mode programmatically. Using it I built the complete solution:

    UiAutomation uiAutomation = InstrumentationRegistry.getInstrumentation().getUiAutomation();
    //enter multi-window mode
    uiAutomation.performGlobalAction(AccessibilityService.GLOBAL_ACTION_TOGGLE_SPLIT_SCREEN);
    //wait for completion, unfortunately waitForIdle doesn't applicable here
    Thread.sleep(1000);
    //simulate selection of our activity
    MotionEvent motionDown = MotionEvent.obtain(SystemClock.uptimeMillis(), SystemClock.uptimeMillis(), KeyEvent.ACTION_DOWN,
            150, 200, 0);
    motionDown.setSource(InputDevice.SOURCE_TOUCHSCREEN);
    uiAutomation.injectInputEvent(motionDown, true);
    motionDown.recycle();
    MotionEvent motionUp = MotionEvent.obtain(SystemClock.uptimeMillis(), SystemClock.uptimeMillis(), KeyEvent.ACTION_UP,
            150, 200, 0);
    motionUp.setSource(InputDevice.SOURCE_TOUCHSCREEN);
    uiAutomation.injectInputEvent(motionUp, true);
    motionUp.recycle();
    //perform test actions below

As you can see, there are two workarounds:

1. We can't use uiAutomation.waitForIdle to wait entering multi-mode completion
2. I haven't found a way to select an application in task manager to request focus to our activity. So I just perform some touch event on the possible location of our activity.

After implementing it you'll be able to test the activity as usual with Espresso etc.

Answered By - Beloo