Class no longer obfuscated after upgrading to Android Gradle plugin 3.4.0

Question

After upgrading to Android Gradle plugin 3.4.0, a basic class no longer gets obfuscated.

The following basic steps can reproduce the problem:

1. In Androi

Answer 1

The solution from @shizhen is what I accepted as the solution to the problem. But I wanted to document an alternative in case anyone else runs into this problem.

I was able to make R8 obfuscate the class by actually instantiating the class. Notice how my original code for ProguardTestClass contained no constructor and I used it in a fairly static way. But when I added a constructor and instantiated it from MainActivity.java, that gave R8 a reason to obfuscate it I guess.

Revised ProguardTestClass that made R8 perform the obfuscation:

public class ProguardTestClass {

    //
    // NEW CODE: BEGIN
    //
    private int avar;

    public ProguardTestClass(int avar) {
        this.avar = avar;
    }

    public int incrementValue() {
        return ++avar;
    }
    //
    // NEW CODE: END
    //

    public interface ProguardTestInnerInterface {
        void proguardTestCallback(String message);
    }

    public static void proguardTestMethod(String input, ProguardTestInnerInterface impl) {
        impl.proguardTestCallback("proguardTestMethod received input=[" + input + "]");
    }
}

Then in MainActivity.java I instantiated and called the ProguardTestClass on onCreate():

    proguardTestClass = new ProguardTestClass(3);
    Log.d(TAG, "Proguard test: " + proguardTestClass.incrementValue());