Stop accessing non-public fields in Fragment

After updating the support library of my project to the new AndroidX scheme, the app started crashing after calling this method: BackstackAccessor.isFragmentOnBackStack(Fragment()) Crash: java.lang.IllegalAccessError: Method 'boolean androidx.fragment.app.Fragment.isInBackStack()' is inaccessible to class 'androidx.core.app.BackstackAccessor'

After some investigation, I found that the issue is this file: https://github.com/sockeqwe/mosby/blob/master/utils-fragment/src/main/java/android/support/v4/app/BackstackAccessor.java which is accessing a non-public field by “faking” the package.

As well as being a bad practice, this stops working after migrating to AndroidX due to the change of package names.

Ideally this should be reverted to the commented-out version of the code still existing in the linked file.

[tommus]

AndroidX is now stable 1.0.0. Even more, Google wrote that the Support 28.0.0 is the last version that supports android.support package. It is time to move on.

[drampelt]

As a temporary workaround until then for those who want to continue using AndroidX, you can exclude the utils-fragment module dependency in your build.gradle:

compile 'com.hannesdorfmann.mosby3:mvi:3.1.0' {
    exclude group: 'com.hannesdorfmann.mosby3', module: 'utils-fragment'
}

and then define your own androidx.core.app.BackstackAccessor class:

package androidx.core.app;

import androidx.fragment.app.Fragment;

public class BackstackAccessor {
    public static boolean isFragmentOnBackStack(Fragment fragment) {
        return false;
    }
}