IssueTracker

We are developing an SDK and want to obfuscate it with minifyEnabled=true.

However, when an application is launched with the obfuscated SDK, it crashes with the following error:

java.lang.LinkageError: Method int com.example.mylibrary.NavBarScrollingBehaviour.getOverlayTop() overrides final method in class Lcom/google/android/material/appbar/HeaderScrollingViewBehavior; (declaration of 'com.example.mylibrary.NavBarScrollingBehaviour' appears in /data/data/com.example.bugexample/code_cache/.overlay/base.apk/classes2.dex)

To simplify the issue, we have provided BugExample.zip in attachments, which contains a minimal reproducible example.

• The project consists of two modules: :app and :mylibrary.
  • :mylibrary is an SDK that we want to obfuscate;
  • :app is demo application that integrates this SDK;
• In :mylibrary module, we have two classes: NavBarScrollingBehaviour and NavBarUsage;
• NavBarScrollingBehaviour extends AppBarLayout.ScrollingViewBehavior which itself extends HeaderScrollingViewBehavior;
• HeaderScrollingViewBehavior has two final methods setOverlayTop and getOverlayTop;
• In NavBarUsage class these two methods are used;
• After building :mylibrary, the generated mapping.txt file contains two suspicious lines:

int getOverlayTop() -> getOverlayTop
      # {"id":"com.android.tools.r8.synthesized"}
void setOverlayTop(int) -> setOverlayTop
      # {"id":"com.android.tools.r8.synthesized"}

Looks like R8 adds these two synthetic methods during obfuscation and optimization which conflict with the original final methods from HeaderScrollingViewBehavior.

If we slightly modify NavBarScrollingBehaviour code as follows, the crash disappears:

internal class NavBarScrollingBehaviour : AppBarLayout.ScrollingViewBehavior() {

    @get:JvmName("getInternalOverlayTop")
    @set:JvmName("setInternalOverlayTop")
    var overlayTop: Int
        set(value) {
            (this as AppBarLayout.ScrollingViewBehavior).setOverlayTop(value)
        }
        get() {
            return (this as AppBarLayout.ScrollingViewBehavior).getOverlayTop()
        }
}

Is there a way to prevent R8 from adding these synthetic methods during obfuscation adn optimization?