Crash when removing a controller on onAttach() (When it has nested Controllers)

[sgc-code]

You can reproduce the issue if you try to pop a Controller from the backstack in the onAttach method. It's also needed that the Controller you are popping has a nested controller.

java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.ViewParent android.view.View.getParent()' on a null object reference
        at com.bluelinelabs.conductor.Controller.attach(Controller.java:885)
        at com.bluelinelabs.conductor.Controller$7.onAttached(Controller.java:1029)
        at com.bluelinelabs.conductor.internal.ViewAttachHandler.reportAttached(ViewAttachHandler.java:87)
        at com.bluelinelabs.conductor.internal.ViewAttachHandler$1.onAttached(ViewAttachHandler.java:47)
        at com.bluelinelabs.conductor.internal.ViewAttachHandler$2.onViewAttachedToWindow(ViewAttachHandler.java:126)
        at android.view.View.dispatchAttachedToWindow(View.java:13536)
        at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:2688)
        at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:2695)
        at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:2695)
        at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:2695)
        at android.view.ViewGroup.addViewInner(ViewGroup.java:3975)
        at android.view.ViewGroup.addView(ViewGroup.java:3786)
        at android.view.ViewGroup.addView(ViewGroup.java:3727)
        at android.view.ViewGroup.addView(ViewGroup.java:3700)
        at com.bluelinelabs.conductor.changehandler.SimpleSwapChangeHandler.performChange(SimpleSwapChangeHandler.java:73)
        at com.bluelinelabs.conductor.ControllerChangeHandler.executeChange(ControllerChangeHandler.java:204)
        at com.bluelinelabs.conductor.ControllerChangeHandler.executeChange(ControllerChangeHandler.java:154)
        at com.bluelinelabs.conductor.Router.performControllerChange(Router.java:816)
        at com.bluelinelabs.conductor.Router.performControllerChange(Router.java:786)
        at com.bluelinelabs.conductor.Router.performControllerChange(Router.java:768)
        at com.bluelinelabs.conductor.Router.popController(Router.java:137)
        at com.bluelinelabs.conductor.Router.popCurrentController(Router.java:119)
        at com.bluelinelabs.conductor.Router.handleBack(Router.java:97)
        at com.example.cnvci.conductornestedissue.MainActivity.onBackPressed(MainActivity.kt:23)

I did some debugging and I suspect it can be related to the the ViewAttachHandler, and a horrible workaround is to add an empty view as the deepest child of the parent Controller.

The ViewAttachHandler handler was written to fix a similar issue (#201), and I've also found these two issues that can be related: #407, #426

Here there's a minimal project demonstrating the issue. https://github.com/sgc-code/ConductorNestedIssue

[Wrywulf]

There doesn't seem to be much activity here. Does anyone have any updates?

I believe I am seeing the same issue using conductor 3.0.0-rc6. At least the same NPE. Cannot say for sure that the preconditions are the same (crashlytics issue).

In any case, the View is annotated with @Nonnull in Controller.attach() so I assume that it needs to be fixed in Conductor - or that the nullability contract is wrong?

[DaniilKharin32]

Can you please tell me if there is any workaround to solve this problem for version 2.1.5?