编写自定义注释和.java文件创建

Question

我想制作自己的Annotation，我希望它能创建.java文件。为此，我使用

@Retention(RetentionPolicy.CLASS)

但是，我无法理解如何在处理器中触发处理器和init方法？我想它必须在编译时创建.java文件。但它没有。如何触发Annotation创建.java文件？

我在Android工作室做了一切，我改变了gradle来编译这个像java。

这是处理器代码：

@Override
public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {

    for (Element annotatedElement : roundEnv.getElementsAnnotatedWith(Factory.class)) {

        if (annotatedElement.getKind() != ElementKind.CLASS) {
            error(annotatedElement, "Only classes can be annotated with @%s", Factory.class.getSimpleName());
            return true;
        }

        TypeElement typeElement = (TypeElement) annotatedElement;

        try {

            FactoryAnnotatedClass annotatedClass = new FactoryAnnotatedClass(typeElement);

            if (!isValidClass(annotatedClass)) {
                return true;
            }

            FactoryGroupedClasses factoryClass = factoryClasses.get(annotatedClass.getQualifiedFactoryGroupName());

            if (factoryClass == null) {
                String qualifiedGroupName = annotatedClass.getQualifiedFactoryGroupName();
                factoryClass = new FactoryGroupedClasses(qualifiedGroupName);
                factoryClasses.put(qualifiedGroupName, factoryClass);
            }

            factoryClass.add(annotatedClass);

        } catch (IllegalArgumentException e) {
            error(typeElement, e.getMessage());
            return true;
        } catch (IdAlreadyUsedException e) {
            FactoryAnnotatedClass existing = e.getExisting();
            // Already existing
            error(annotatedElement,
                    "Conflict: The class %s is annotated with @%s with id ='%s' but %s already uses the same id",
                    typeElement.getQualifiedName().toString(), Factory.class.getSimpleName(),
                    existing.getTypeElement().getQualifiedName().toString());
            return true;
        }




    }

    try {

        for (FactoryGroupedClasses factoryClass : factoryClasses.values()) {
            factoryClass.generateCode(elementUtils, filer);
        }

        factoryClasses.clear();

    } catch (IOException e) {
        error(null, e.getMessage());
    }

    return true;
}



  @Override
public synchronized void init(ProcessingEnvironment processingEnv) {
    super.init(processingEnv);

    typeUtils = processingEnv.getTypeUtils();
    elementUtils = processingEnv.getElementUtils();
    filer = processingEnv.getFiler();
    messager = processingEnv.getMessager();

}