将通用类和对象传递给Java方法

Question

I want to replace the following with generics:

• for (Post post : postResponse.getResults()) { , where Post can be any POJO.
• List<Post> posts = postResponse.getResults(); where List<Post> can be a list of anything I pass into it.

What would my method call and method body look like?

Different examples of method calls:

retrieveData(mCardAdapter, new Post(), Post.class);
retrieveData(mCardAdapter, new Contact(), Contact.class);
retrieveData(mCardAdapter, new Product(), Product.class);
retrieveData(mCardAdapter, new Booking(), Booking.class);

Method:

private void retrieveData(final CardAdapter mCardAdapter, final Object<T> postObject, Class<T> postClass) {
        RetrofitService service = ServiceFactory.createRetrofitService(RetrofitService.class, RetrofitService.SERVICE_ENDPOINT);
        service.getPosts()
                .subscribeOn(Schedulers.newThread())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Subscriber<PostResponse>() {
                    @Override
                    public final void onCompleted() {
                        setRefreshingFalse();
                        Log.e("RetrofitService", "Retrofit Request Completed!");
                    }

                    @Override
                    public final void onError(Throwable e) {
                        setRefreshingFalse();
                        Log.e("RetrofitService", e.getMessage());
                    }

                    @Override
                    public final void onNext(PostResponse postResponse) {
                        if (postResponse != null) {

                            Log.e("RetrofitService", "Returned objects: " + postResponse.getResults());

                            for (postObject post : postResponse.getResults()) {
                                Log.e("RetrofitService", post.getObjectId() + ": " + post.getText());
                            }

                            setRefreshingFalse();

                            mCardAdapter.clear();
                            List<postClass> posts = postResponse.getResults();
                            mCardAdapter.addData(posts);

                        } else {
                            Log.e("RetrofitService", "Object returned is null.");
                        }

                    }

                });
    }

I'm getting Unknown class: 'tClass' and Unknown class: 'postClass' . Obviously this is not the way to do it so perhaps treat what I've shown above as pseduo-code. Does it makes sense what I'm trying to? I really want to generify this retrieveData method so that I can be used to query differences classes.

To help with understanding. What I want to avoid:

retrievePosts(mCardAdapter);
retrieveUsers(mCardAdapter);

private void retrievePosts(final CardAdapter mCardAdapter) {
        RetrofitService service = ServiceFactory.createRetrofitService(RetrofitService.class, RetrofitService.SERVICE_ENDPOINT);
        service.getPosts()
                .subscribeOn(Schedulers.newThread())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Subscriber<PostResponse>() {
                    @Override
                    public final void onCompleted() {
                        setRefreshingFalse();
                        Log.e("RetrofitService", "Retrofit Request Completed!");
                    }

                    @Override
                    public final void onError(Throwable e) {
                        setRefreshingFalse();
                        Log.e("RetrofitService", e.getMessage());
                    }

                    @Override
                    public final void onNext(PostResponse postResponse) {
                        if (postResponse != null) {
                            Log.e("RetrofitService", "Returned objects: " + postResponse.getResults());

                            for (Post post : postResponse.getResults()) {
                                Log.e("RetrofitService", post.getObjectId() + ": " + post.getText());
                            }

                            /*for (Post post : postResponse.getResults()) {
                                mCardAdapter.addData(post);
                            }*/

                            setRefreshingFalse();

                            mCardAdapter.clear();
                            List<Post> posts = postResponse.getResults();
                            mCardAdapter.addData(posts);

                        } else {
                            Log.e("RetrofitService", "Object returned is null.");
                        }

                    }

                });
    }

    private void retrieveUsers(final CardAdapter mCardAdapter) {
        RetrofitService service = ServiceFactory.createRetrofitService(RetrofitService.class, RetrofitService.SERVICE_ENDPOINT);
        service.getUsers()
                .subscribeOn(Schedulers.newThread())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Subscriber<PostResponse>() {
                    @Override
                    public final void onCompleted() {
                        setRefreshingFalse();
                        Log.e("RetrofitService", "Retrofit Request Completed!");
                    }

                    @Override
                    public final void onError(Throwable e) {
                        setRefreshingFalse();
                        Log.e("RetrofitService", e.getMessage());
                    }

                    @Override
                    public final void onNext(PostResponse postResponse) {
                        if (postResponse != null) {
                            Log.e("RetrofitService", "Returned objects: " + postResponse.getResults());

                            for (User user : userResponse.getResults()) {
                                Log.e("RetrofitService", user.getObjectId() + ": " + user.getText());
                            }

                            /*for (Post post : postResponse.getResults()) {
                                mCardAdapter.addData(post);
                            }*/

                            setRefreshingFalse();

                            mCardAdapter.clear();
                            List<User> users = userResponse.getResults();
                            mCardAdapter.addData(users);

                        } else {
                            Log.e("RetrofitService", "Object returned is null.");
                        }

                    }

                });
    }

Answer 1

If I understood your question correctly you want to have a generic method for different classes. I did not see that you are adding something to the List so this might work for you.

private <clazz> void retrieveData(final Class<?> clazz) {
 for (clazz post : postResponse.getResults()) {
    // you can't do anything here since clazz can be anything
  }
  List<clazz> posts = postResponse.getResults();
}