Workers cannot be instantiated with NoSuchMethodException in minified variant

Question

I am using Android's WorkManager for background tasks and everything works great until I am trying to use it in a minified build. When the service should be initialized I am getting the following exception:

Could not instantiate *REDACTED*Worker
                                                                                                    java.lang.NoSuchMethodException: *REDACTED*Worker.<init> [class android.content.Context, class androidx.work.WorkerParameters]
                                                                                                        at java.lang.Class.getConstructor0(Class.java:2328)
                                                                                                        at java.lang.Class.getDeclaredConstructor(Class.java:2167)
                                                                                                        at e1.y.b(SourceFile:65)
                                                                                                        at f1.j.k(SourceFile:358)
                                                                                                        at f1.j.run(SourceFile:17)
                                                                                                        at n1.i$a.run(SourceFile:3)

• I have followed the required steps for Custom WorkManager Configuration and Initialization, but still getting this issue for minified build.

• I am using Dagger2 (not Hilt) and RxWorker

• I am providing a custom WorkerFactory implementation.

• Gradle:

...
// workVersion is 2.7.1
implementation "androidx.work:work-rxjava2:$workVersion"
implementation "androidx.work:work-runtime-ktx:$workVersion"

• Manifest:

<application
>
 ...
 <provider
      android:name="androidx.startup.InitializationProvider"
      android:authorities="${applicationId}.androidx-startup"
      android:exported="false"
      tools:node="remove" />

I found a similar question which refers to older version and suggests to add the following to the proguard file:

-keepclassmembers class * extends androidx.work.Worker {
    public <init>(android.content.Context,androidx.work.WorkerParameters);
}

But that doesn't solve the issue.

Answer 1

After debugging this issue I found out that my custom factory was invoked, but it threw an exception that I caught inside a try-catch block (thus I didn't see it in the logs) and returned null. When the custom factory returns null, it falls back to use reflection.