android 单元测试 + robolectric 3.0 + java.lang.LinkageError：加载器约束违规

Question

Error:

java.lang.LinkageError: loader constraint violation: when resolving method "com.example.demo.utils.R.init(Landroid/content/Context;)V" the class loader (instance of org/robolectric/internal/bytecode/InstrumentingClassLoader) of the current class, com/example/test/FirstTest, and the class loader (instance of sun/misc/Launcher$AppClassLoader) for the method's defining class, com/example/demo/utils/R, have different Class objects for the type android/content/Context used in the signature

test code:

    @runwith(RobolectricGradleTestRunner.class)
    @config(constants = BuildConfig.class,sdk = 21,application = TestApplication.class)
    public class FirstTest{
            @test
            public void testCase01(){
                 MainActivity mainActivity =  Robolectric.setupActivity(MainActivity.class);
                ....
           }
        }

build.gradle:

dependencies {
    testCompile 'junit:junit:4.12'
    testCompile "org.robolectric:robolectric:3.0"
    testCompile 'org.robolectric:shadows-httpclient:3.0'
...
}

src/test/java/.../TestApplication:

    public class TestApplication extends Application {
    }

com/example/demo/MainActivity:

    public class MainActivity extends Activity {
        @override
        protected void onCreate(Bundle savedInstanceState) {
        ...
        com.example.demo.utils.R.init(getApplicationContext());
        ...
        }
    }

com/example/demo/utils/R:

    public final class R {
        public static Resources resources;
        private static String packageName;
        public static void init(Context paramContext) {
           resources = paramContext.getResources();
           packageName = paramContext.getPackageName();
        }
    ...
    }

Answer 1

I find the reason why tests run fail is using a class named com.example.demo.utils.R , which has a conflict with an R class autogenerated by the Android System. If you rename R to another name, like Ra , it works.