The specified child already has a parent. You must call removeView() on the child's parent first.

Thread Name: 'main' Back traces starts. java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first. at android.view.ViewGroup.addViewInner(ViewGroup.java:5264) at android.view.ViewGroup.addView(ViewGroup.java:5093) at androidx.viewpager.widget.ViewPager.addView(ViewPager.java:1485) at android.view.ViewGroup.addView(ViewGroup.java:5030) at androidx.fragment.app.FragmentStateManager.addViewToContainer(FragmentStateManager.java:833) at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:523) at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:282) at androidx.fragment.app.FragmentStore.moveToExpectedState(FragmentStore.java:112) at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1647) at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:3128) at androidx.fragment.app.FragmentManager.dispatchActivityCreated(FragmentManager.java:3072) at androidx.fragment.app.FragmentController.dispatchActivityCreated(FragmentController.java:251) at androidx.fragment.app.FragmentActivity.onStart(FragmentActivity.java:502) at androidx.appcompat.app.AppCompatActivity.onStart(AppCompatActivity.java:246) at com.trello.rxlifecycle4.components.support.RxAppCompatActivity.onStart(RxAppCompatActivity.java:80) at cn.droidlover.xdroidmvp.mvp.XActivity.onStart(XActivity.java:89) at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1468) at android.app.Activity.performStart(Activity.java:8224) at android.app.ActivityThread.handleStartActivity(ActivityThread.java:3799) at android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:221) at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:201) at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:173) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2291) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loopOnce(Looper.java:211) at android.os.Looper.loop(Looper.java:300) at android.app.ActivityThread.main(ActivityThread.java:8322) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:556) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1038) Back traces ends.