Detect a fragment in ViewPager - kotlin

Question

I have a viewpager and it contains a fragment. In my application there are two tabs and fragments are changing according to tab switch.
When I want to check that the correct fragment is opened in the tab change, I get the following error because code can't find the fragment inside the viewpager.
Error part is:
java.lang.RuntimeException: java.lang.NullPointerException: Cannot run onActivity since Activity has been destroyed already
at androidx.test.runner.MonitoringInstrumentation.runOnMainSync(MonitoringInstrumentation.java:450)
at androidx.test.core.app.ActivityScenario.onActivity(ActivityScenario.java:673)
at dashboard.test.DashboardNavigationTests$CheckBothTabsAreSwitchable$1$3.invoke(DashboardNavigationTests.kt:136)
at dashboard.test.DashboardNavigationTests$CheckBothTabsAreSwitchable$1$3.invoke(DashboardNavigationTests.kt:135)
at com.kaspersky.kaspresso.testcases.core.testcontext.TestContext.step(TestContext.kt:39)
at dashboard.test.DashboardNavigationTests$CheckBothTabsAreSwitchable$1.invoke(DashboardNavigationTests.kt:135)
at dashboard.test.DashboardNavigationTests$CheckBothTabsAreSwitchable$1.invoke(DashboardNavigationTests.kt:126)
at com.kaspersky.kaspresso.testcases.core.TestRunner.runMainTestSection(TestRunner.kt:144)
at com.kaspersky.kaspresso.testcases.core.TestRunner.run(TestRunner.kt:58)
at com.kaspersky.kaspresso.testcases.core.sections.MainTestSection.run(MainTestSection.kt:29)
at com.kaspersky.kaspresso.testcases.api.testcase.BaseTestCase.run(BaseTestCase.kt:90)
at com.kaspersky.kaspresso.testcases.api.testcase.BaseTestCase.run$default(BaseTestCase.kt:86)
at dashboard.test.DashboardNavigationTests.CheckBothTabsAreSwitchable(DashboardNavigationTests.kt:126)
at java.lang.reflect.Method.invoke(Native Method)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at androidx.test.internal.runner.junit4.statement.RunBefores.evaluate(RunBefores.java:80)
at androidx.test.internal.runner.junit4.statement.RunAfters.evaluate(RunAfters.java:61)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runners.Suite.runChild(Suite.java:128)
at org.junit.runners.Suite.runChild(Suite.java:27)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
at androidx.test.internal.runner.TestExecutor.execute(TestExecutor.java:56)
at androidx.test.runner.AndroidJUnitRunner.onStart(AndroidJUnitRunner.java:395)
at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:2205)
Caused by: java.lang.NullPointerException: Cannot run onActivity since Activity has been destroyed already
at androidx.test.internal.util.Checks.checkNotNull(Checks.java:41)
at androidx.test.core.app.ActivityScenario.lambda$onActivity$2$ActivityScenario(ActivityScenario.java:658)
at androidx.test.core.app.ActivityScenario$$Lambda$4.run(Unknown Source:4)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:462)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at android.app.Instrumentation$SyncRunnable.run(Instrumentation.java:2223)
at android.os.Handler.handleCallback(Handler.java:938)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
And my code block is
#Test
fun CheckBothTabsAreSwitchableAndVerifyFragments() = run {
step("Navigate to Dashboard") {
this#DashboardNavigationTests.NavigateToWelcomePageToDashboard()
}
step("click map tab") {
dashboardScreen.clickMapTab()
}
step("check current fragment is dashboard fragment ") {
activityScenario?.onActivity {
val nextFragment = it.getLastFragment()
assertTrue(nextFragment::class.java == DetectionMapFragment::class.java)
}
}
step("click detection tab") {
dashboardScreen.clickDetectionsTab()
}
step("check current fragment is dashboard fragment") {
activityScenario?.onActivity {
val nextFragment = it.getLastFragment()
assertTrue(nextFragment::class.java == DashboardFragment::class.java)
}
}
}
Could you help me to find fragment in viewpager?
Thank you for your guidance.