Generate Kotlin extension code and not working... X(

MyProcessor.java

package com.example;

import com.google.auto.service.AutoService;
import com.google.common.collect.Sets;

import java.io.IOException;
import java.io.OutputStream;
import java.io.Writer;
import java.util.Set;

import javax.annotation.processing.AbstractProcessor;
import javax.annotation.processing.ProcessingEnvironment;
import javax.annotation.processing.Processor;
import javax.annotation.processing.RoundEnvironment;
import javax.lang.model.element.Element;
import javax.lang.model.element.TypeElement;
import javax.annotation.processing.Filer;
import javax.tools.FileObject;
import javax.tools.JavaFileObject;
import javax.tools.StandardLocation;

@AutoService(Processor.class)
public class MyProcessor extends AbstractProcessor {
    private Filer filer;
    @Override
    public Set<String> getSupportedAnnotationTypes() {
        return Sets.newHashSet(MyAnnotation.class.getCanonicalName());
    }

    @Override
    public synchronized void init(ProcessingEnvironment processingEnv) {
        super.init(processingEnv);
        filer = processingEnv.getFiler();
    }

    @Override
    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
        try {
            FileObject file = filer.createResource(StandardLocation.SOURCE_OUTPUT, "net.kikuchy.kaptapttest", "MainActivityExtension.kt", new Element[0]);
            Writer writer = file.openWriter();
            writer.append("package net.kikuchy.kaptapttest\n\nfun MainActivity.doSomething() = intent");
            writer.flush();
            writer.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return false;
    }
}