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Fixes internal bug b/303652511 and includes a regression test. The TL;DR of the bug is that when re-launching a singleton-cached-engine Flutter activity using FLAG_ACTIVITY_CLEAR_TASK, the teardown of the previous Flutter activity interleaves with the creation of the new Flutter activity, resulting in the Flutter engine ending up incorrectly in the AppLifecycleState.detached state. This then results in the app being completely unresponsive because Flutter doesn't draw frames in this state. I don't know if the issue is reproducible in production under normal user operation, but I'm concerned it very easily could be. There's also nothing stopping other apps or Android system code from launching an app using this flag.
Unit testing Java code
All Java code in the engine should now be able to be tested with Robolectric 4.10.3 and JUnit 4. The test suite has been added after the bulk of the Java code was first written, so most of these classes do not have existing tests. Ideally code after this point should be tested, either with unit tests here or with integration tests in other repos.
Adding a new test
- Create a file under
test/matching the path and name of the class under test. For example,shell/platform/android/io/flutter/util/Preconditions.java->shell/platform/android/**test**/io/flutter/util/Preconditions**Test**.java. - Add your file to the
sourcesof therobolectric_testsbuild target in/shell/platform/android/BUILD.gn. This compiles the test class into the test jar. - Import your test class and add it to the
@SuiteClassesannotation inFlutterTestSuite.java. This makes sure the test is actually executed at run time. - Write your test.
- Build and run with
testing/run_tests.py [--type=java] [--java-filter=<test_class_name>].
Note that testing/run_tests.py does not build the engine binaries; instead they
should be built prior to running this command and also when the source files
change. See Compiling the engine
for details on how to do so.
Q&A
My new test won't run. There's a "ClassNotFoundException".
See Updating Embedding Dependencies.