我是Android和MVP的新手,在过去的一年半里我一直在做iOS编程,所以我发现委托模式很容易消化。我以这样一种方式实现了MVP,视图符合演示者的协议,这让演示者忽略视图的特定类型,但让它知道某些方法是给定的,因此可以在"视图"上调用。我一直在阅读各种MVP指南,以及所有的Mosby教程,我不确定我是否同意其中的一些。我所实现的模式是犹太的吗?我想要一些反馈,这样我就不会一直朝着不好的方向前进,如果这确实是我正在做的…
例如,基地推荐者:
public abstract class Presenter<V, S> implements BasePresenterInterface<V, S> {
public interface PresenterProtocol extends BasePresenterProtocol {
}
private WeakReference<V> mAttachedView = null;
private S mService = null;
/**
* Interface Overrides
*/
@Override
public void attachView(V view) {
boolean viewDoesNotConform = !viewDoesConform(view);
if (viewDoesNotConform) {
Log.d("DEBUG", "Cannot attach View that does not conform to PresenterProtocol");
return;
}
mAttachedView = new WeakReference<>(view);
((BasePresenterProtocol) getAttachedView()).onViewAttached();
}
@Override
public void detachView() {
mAttachedView = null;
}
@Override
public boolean viewDoesConform(V view) {
Class<?> klass = view.getClass();
boolean conforms = BasePresenterInterface.BasePresenterProtocol.class.isAssignableFrom(klass);
return conforms;
}
@Override
public boolean viewIsAttached() {
return mAttachedView != null;
}
@Override
public V getAttachedView() {
return mAttachedView.get();
}
@Override
public S getService() {
return mService;
}
@Override
public void setService(S service) {
mService = service;
}
}
然后将其子类化为如下:
PhotoRecyclerPresenter:
public class PhotoRecyclerPresenter extends Presenter<PhotoRecyclerPresenter.PhotoRecyclerPresenterProtocol, PhotoService> {
public interface PhotoRecyclerPresenterProtocol extends Presenter.PresenterProtocol {
void onPhotosLoaded(List<TestPhoto> photoList);
void onItemSelected(TestPhoto photo);
void onShowDetail(TestPhoto photo);
}
private static PhotoRecyclerPresenter mSharedInstance;
private PhotoRecyclerPresenter() {
setService(new PhotoService());
}
/**
* External Methods
*/
public void getPhotos() {
boolean noAttachedView = !viewIsAttached();
if (noAttachedView) {
Log.d("DEBUG", "No view attached");
return;
}
getService().getAPI()
.getPhotos()
.observeOn(AndroidSchedulers.mainThread())
.subscribe(photoList -> getAttachedView().onPhotosLoaded(photoList));
}
/**
* Internal Methods
*/
public static PhotoRecyclerPresenter getSharedInstance() {
boolean firstInstance = mSharedInstance == null;
if (firstInstance) {
setSharedInstance(new PhotoRecyclerPresenter());
}
return mSharedInstance;
}
public static void setSharedInstance(PhotoRecyclerPresenter instance) {
mSharedInstance = instance;
}
public void didSelectItem(TestPhoto photo) {
getAttachedView().showDetail(photo);
}
}
它与视图通信: PhotoRecyclerFragment:
public class PhotoRecyclerFragment extends Fragment implements PhotoRecyclerPresenter.PhotoRecyclerPresenterProtocol {
private RecyclerView mRecyclerView;
private RecyclerView.LayoutManager mLayoutManager;
private Activity mParentActivity;
private PhotoRecyclerPresenter mPresenter;
private PhotoRecyclerAdapter mAdapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_recycler, container, false);
mParentActivity = getActivity();
mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recyclerView);
mLayoutManager = new LinearLayoutManager(mParentActivity);
mAdapter = new PhotoRecyclerAdapter(this);
mRecyclerView.setLayoutManager(mLayoutManager);
mRecyclerView.setAdapter(mAdapter);
mPresenter = PhotoRecyclerPresenter.getSharedInstance();
mPresenter.attachView(this);
return rootView;
}
@Override
public void onDestroyView() {
super.onDestroyView();
mPresenter.detachView();
mAdapter.clear();
}
/**
* PhotoRecyclerPresenterProtocol Methods
*/
@Override
public void onItemSelected(TestPhoto photo) {
mPresenter.didSelectItem(photo);
}
@Override
public void onPhotosLoaded(List<TestPhoto> photoList) {
mAdapter.loadPhotos(photoList);
}
@Override
public void onViewAttached() {
mPresenter.getPhotos();
}
@Override
public void onViewDetached() {
}
@Override
public void onShowDetail(TestPhoto photo) {
Intent detailIntent = new Intent(mParentActivity, PhotoDetailActivity.class);
mParentActivity.startActivity(detailIntent.putExtra(Intent.EXTRA_UID, photo.getPhotoId()));
}
}
这让我定义了一组视图需要遵守的要求,以便使用单例呈现器,同时保持呈现器不知道哪些视图使用它,只要它们符合它的协议。到目前为止,在我的实践项目中,它似乎工作得很好,但我似乎找不到任何资源,在那里我正在做的事情被推荐为MVP,我有足够的自我怀疑,我想我会问我的第一个StackOverflow问题。有MVP经验的人能解释一下吗?
另外,如果我问错了地方,请告诉我正确的地方。
谢谢:)
在我看来,你正在做和Mosby做的一样的事情。唯一的区别是接口(或objective-c中的协议)的名称。你叫它PresenterProtocol
,而莫斯比叫它MvpView
。两者都在做同样的工作:为Presenter
提供演示者可以调用的方法Api来操作视图。
唯一没有意义的是有一个方法viewDoesConform()
。在Java中有类型安全。你可以使用你的演示器的泛型类型V
来确保你的片段正在实现演示器的协议。把它改成V extends BasePresentersProtocol
此外,我认为拥有演示者的"共享实例"(也称为单例模式)是没有意义的。我认为拥有PhotoService的"共享实例"会更有意义。但也请注意,这样做你的代码是不可测试的(单元测试)了。你应该谷歌一下"依赖注入"或"控制逆",了解如何编写模块化、可重用和可测试的代码。我说的不是像Dagger、spring或guice这样的依赖注入框架。您只需要理解依赖注入背后的思想。你可以完全按照这个原则编写类,而不需要依赖注入框架(即使用构造函数参数)。
旁注:你永远不能从PhotoService取消订阅你的演示者。根据PhotoService的实现方式,你可能会有内存泄漏,因为PhotoService的可观察对象有一个对演示者的引用,这会阻止演示者和PhotoService(取决于你的具体实现)被垃圾收集。
编辑:Mosby定义了View的协议。请查看项目网站上的入门部分。HelloWorldView
定义了两个方法:showHello()
和showGoodbye()
(由HelloWorldActivity
实现),HelloWorldPresenter
调用这两个方法来操作视图。HelloWorldPresenter
还取消异步请求以避免内存泄漏。你也应该这样做。否则,你的演示器只能在改造httpcall完成后被垃圾收集。