How to stop and restart an activity in an android instrumentation test?

Question

I'm trying to write an Android activity instrumentation test that stops (onPause(), then onStop()) and restarts the current activity. I tried

activity.finish();
activity = getActivity();

...but that doesn't seem to work properly.

The goal of the test is to assert that form data is stored during the onPause() method and re-read during the onStart() method. It works when doing it manually, but the test fails, from which I draw the conclusion that activity.finish() seems to be the wrong way to stop and restart an activity.

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Edit: My main problem seems to have been a synchronization issue. After restarting the activity, the test runner didn't wait for all event handlers to finish. The following line halts the test execution until the activity is idle:

getInstrumentation().waitForIdleSync()

Besides that, take a look at the accepted answer for more valuable information about the lifecycle.

Answer 1

By calling (or trigger a screen orientation change):

activity.finish(); // old activity instance is destroyed and shut down.
activity = getActivity(); // new activity instance is launched and created.

Causing the activity go through the complete recreation life cycle:

onPause() -> onStop() -> onDestroy() -> onCreate()

What you need is:

onPause() -> onStop() -> onRestart()

I exposed the Instrumentation API recently and found plenty of interesting activity life cycle trigger method callActivityOnXXX(), the following single line of code should do the tricky:

MyActivity myActivity = getActivity();
// make activity falling into restart phase:
getInstrumentation().callActivityOnRestart(myActivity);

Activity life cycle diagram quoting from official dev guide: