mosby Mvp框架分析

A Model-View-Presenter / Model-View-Intent library for modern Android apps。
github项目地址：https://github.com/sockeqwe/mosby
集成：

 dependencies {
  compile 'com.hannesdorfmann.mosby3:mvi:3.1.0' // Model-View-Intent
  // or
  compile 'com.hannesdorfmann.mosby3:mvp:3.1.0' // Plain MVP
  / / or
  compile 'com.hannesdorfmann.mosby3:viewstate:3.1.0' // MVP + ViewState support
}

此篇文章只分析mvp这套框架，便于理解mvp结构。

MvpActivity<V, P>：Activity基类。V和P分别代表V模块与P模块。

public abstract class MvpActivity<V extends MvpView, P extends MvpPresenter<V>>
extends AppCompatActivity implements MvpView,
com.hannesdorfmann.mosby3.mvp.delegate.MvpDelegateCallback<V,P> {

 protected ActivityMvpDelegate mvpDelegate;
 protected P presenter;
 protected boolean retainInstance;

@Override protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getMvpDelegate().onCreate(savedInstanceState);
}

@Override protected void onDestroy() {
  super.onDestroy();
  getMvpDelegate().onDestroy();
}

@Override protected void onSaveInstanceState(Bundle outState) {
  super.onSaveInstanceState(outState);
  getMvpDelegate().onSaveInstanceState(outState);
}

@Override protected void onPause() {
  super.onPause();
  getMvpDelegate().onPause();
}

@Override protected void onResume() {
  super.onResume();
  getMvpDelegate().onResume();
}

@Override protected void onStart() {
  super.onStart();
  getMvpDelegate().onStart();
}

@Override protected void onStop() {
  super.onStop();
  getMvpDelegate().onStop();

主要是借助Activity生命周期通过getMvpDelegate代理类对mvp结构进行调度。
看下getMvpDelegate（）的实现：

 @NonNull protected ActivityMvpDelegate<V, P> getMvpDelegate() {
if (mvpDelegate == null) {
  mvpDelegate = new ActivityMvpDelegateImpl(this, this, true);
}
  return mvpDelegate;
}  

可以看出具体的操作是在ActivityMvpDelegateImpl实现的。
再看oncreate()初始化： getMvpDelegate().onCreate(savedInstanceState);里面的重要方法是createViewIdAndCreatePresenter（）。

private P createViewIdAndCreatePresenter() {

P presenter = delegateCallback.createPresenter();
if (presenter == null) {
  throw new NullPointerException(
      "Presenter returned from createPresenter() is null. Activity is " + activity);
}
if (keepPresenterInstance) {
  mosbyViewId = UUID.randomUUID().toString();
  PresenterManager.putPresenter(activity, mosbyViewId, presenter);
}
return presenter;
}

主要实了Presenter的创建，以及是否因为Activity的意外销毁保留Presenter模块。默认为true为保存Presenter。

P presenter = delegateCallback.createPresenter();

在我们自己的Activity里重写createPresenter方法，创建自己的Presenter。

然后将Presenter 传递到基类Activity,调用方法为：delegateCallback.setPresenter(presenter); getPresenter().attachView(getMvpView());

@UiThread
@Override public void attachView(V view) {
viewRef = new WeakReference<V>(view);
}

将View层保存到WeakReference中，以上Presenter，View层的初始化工作完成。

你也可以重写ActivityMvpDelegateImpl中定义的生命周期实现自己的特殊逻辑。

onDestroy框架中有自己的实现：

@Override public void onDestroy() {
boolean retainPresenterInstance = retainPresenterInstance(keepPresenterInstance, activity);
getPresenter().detachView(retainPresenterInstance);
if (!retainPresenterInstance && mosbyViewId != null) {
  PresenterManager.remove(activity, mosbyViewId);
}

if (DEBUG) {
  if (retainPresenterInstance) {
    Log.d(DEBUG_TAG, "View"
        + getMvpView()
        + " destroyed temporarily. View detached from presenter "
        + getPresenter());
  } else {
    Log.d(DEBUG_TAG, "View"
        + getMvpView()
        + " destroyed permanently. View detached permanently from presenter "
        + getPresenter());
  }
 }
}


@UiThread
@Override public void detachView(boolean retainInstance) {
if (viewRef != null) {
  viewRef.clear();
  viewRef = null;
  }
}  

主要是对View层的销毁释放，相信通过源码的分析，使用起来会很简单。