当我初始化UiDevice时，我得到了一个NullPointerExecption，下面是我的错误信息：
java.lang.NullPointerException:尝试对空对象引用调用虚拟方法“void android.app.UiAutomation.setOnAccessibilityEventListener（android.app.UiAutomation$OnAccessibilityEventListener）”以下是我的代码

代码：

@RunWith(AndroidJUnit4.class)
public class DailyTest  { 

    @Rule
        public ActivityTestRule<MainActivity> activityTestRule = new ActivityTestRule(MainActivity.class, false, true);
    @Before
     public  void  setUp(){
            Instrumentation instrumentation =InstrumentationRegistry.getInstrumentation();
            Log.d(TAG,"instrumentation="+instrumentation);
            UiDevice uiDevice = UiDevice.getInstance(instrumentation);
            Log.d(TAG,"uiDevice="+uiDevice);
    }
}