Why java.lang.NoSuchMethodError when dynamically load a dex jar?

Question

There is a interface IA class in APK file. I create a jar containing IA's implementation MA. The jar has a Global class and B class. The jar is loaded dynamically with Dexclassloader from data directory.

interface IA {
  test();
}

class Global {
   IA instance;  //refer to  MA instance.
}

class B {
  ....
  instance.test() ; // throw NoSuchMethodError
....
}

But it's OK to call instance's test method through reflection.

Why? Surely I am not familiar with some principals of Classloader or DexClassloader. Could someone give explanation for me? Thanks

you have not implemented the method. Interface just has declaration of the method. And you are not using reflection by the way. — codingenious, May 05 '16 at 12:30
@Batty Instance is MA instance which implements the interface IA in apk class — Victor Choy, May 06 '16 at 02:51

score 0 · Answer 1 · answered Jan 27 '18 at 16:28

I too got a NoSuchMethod error, after doing some testing I found out that the problem was that the DEX file inside the JAR wasn't named classes.dex as it's supposed to be. The fact that the app was able to create a new instance of your class doesn't necessarily mean that the DEX was loaded properly, I tested it with an empty JAR (i. e. removed all internal files via 7-ZIP) and was still able to instantiate my class (although I guess it would work only with a default constructor that gets zero parameters).

Why java.lang.NoSuchMethodError when dynamically load a dex jar?

1 Answers1