距离上一篇Android MVP从懵逼到入门：登陆业务实践已经有一段时间了，这段时间忙着公司的项目，都没找时间写写文章，今天就把这段时间整理的MVP知识再总结一下，这篇文章主要介绍我是如何使用MVP模式来实现主页多个Tab切换的场景的。
说是复杂，其实只是多了一些Fragment而已，在上一篇文章中，我们说Activity的主要作用是创建view和presenter，并把view实例传入到presenter中，那么，对于多个Tab切换的主页面（现在的大多数app都是这样的主页），Activity的作用就又多了一个，也是大家都知道的：管理Fragment。其实这没什么想不到的，在没说MVP的时候，大家也都是这么做的。
这里我参考网上网友收集的知乎日报的相关api，使用mvp模式简单的实现了知乎日报主页的内容。先看一下效果：
主页效果图
presenter
先看看presenter怎么写，应该说跟上一篇的实现是一样的，那就得先写好契约类--MainContact.java：
public interface MainContract {
interface Presenter extends BasePresenter {
RootEntity getLatestNews();
RootEntity getSafety();
RootEntity getInterest();
RootEntity getSport();
}
interface View extends BaseView<Presenter> {
void setTitle();
void refresh(List<StoriesEntity> list);
}
}
写好契约类，那么这个模块有哪些主要功能基本都清楚了，看view接口，可以知道，页面可以实现的功能有：
- 1.设置页面标题--setTitle
- 2.刷新页面内容--refresh
看presenter接口，可以知道，model提供了那些数据访问接口：- 1.获取今日日报模块内容- 2.获取网络安全模块内容- 3.获取不许无聊模块内容- 4.获取体育日报模块内容契约类写好后，就可以实现presenter接口了，看看MainPresenter.java类：
public class MainPresenter implements MainContract.Presenter {
private String baseUrl = "http://news-at.zhihu.com";
private MainContract.View mMainView;
private Context mContext;
protected ZhiHuService service;
public MainPresenter(Context context) {
this.mContext = context;
}
public void setView(MainContract.View view) {
this.mMainView = view;
mMainView.setPresenter(this);
mMainView.setTitle();
service = getService();
}
public ZhiHuService getService() {
Retrofit retrofit = new Retrofit.Builder()
.baseUrl(baseUrl)
.addConverterFactory(GsonConverterFactory.create())
.addCallAdapterFactory(RxJavaCallAdapterFactory.create())
.build();
service = retrofit.create(ZhiHuService.class);
return service;
}
@Override
public RootEntity getLatestNews() {
return loadData(service.getLatestNews());
}
@Override
public RootEntity getSafety() {
return loadData(service.getSafety());
}
@Override
public RootEntity getInterest() {
return loadData(service.getInterest());
}
@Override
public RootEntity getSport() {
return loadData(service.getSport());
}
@Override
public void start() {
}
public RootEntity loadData(Observable<RootEntity> observable) {
final RootEntity rootEntity = new RootEntity();
observable.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(Schedulers.io())
.map(new Func1<RootEntity, ArrayList<StoriesEntity>>() {
@Override
public ArrayList<StoriesEntity> call(RootEntity rootEntity) {
return rootEntity.getStories();
}
})
.subscribe(new Subscriber<ArrayList<StoriesEntity>>() {
@Override
public void onCompleted() {
}
@Override
public void onError(Throwable e) {
}
@Override
public void onNext(ArrayList<StoriesEntity> storiesEntities) {
rootEntity.setStories(storiesEntities);
mMainView.refresh(storiesEntities);
}
});
return rootEntity;
}
}
view
view其实才是这篇文章的主题，契约类里面定义的一些接口其实是所有的view实现类的集合，比如这里有4个Fragment页面，每个页面展示的内容是不一样的，需要的接口也不一样，这些接口都需要在契约类里面定义，然后每个Fragment都去实现这个接口，完成对应接口中的内容。
比如这4个Fragment都去实现MainContract.View，各自都实现setTitle和refresh内容，如何还有其他需要实现的接口，同样定义在契约类里面，谁关心这个接口，谁就去实现这个接口，view不必关心接口的调用，只需要实现内容就行了，这在MVP中体现的比较明显：面向接口编程。（我所接触的面向接口编程的另一种场景就是模块化编程，感觉有些类似。）
既然有4个Fragment，那么他们肯定有共同之处，至少他们都是Fragment，何不提取基类呢？这相比大家都能想到--Java语言的三大特性即：封装、继承、多态。
来看看BaseFragment的内容：
public class BaseFragment extends Fragment implements MainContract.View {
@BindView(R.id.lv_news)
ListView mListView;
protected MainContract.Presenter mPresenter;
protected ActionBar mActionBar;
private ZhiHuNewsAdapter mAdapter;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
@Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_main_0, container, false);
ButterKnife.bind(this, view);
return view;
}
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
mAdapter = new ZhiHuNewsAdapter(getContext());
mListView.setAdapter(mAdapter);
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
if (isAdded()) {
mActionBar = ((AppCompatActivity)getActivity()).getSupportActionBar();
setTitle();
}
}
@Override
public void setPresenter(MainContract.Presenter presenter) {
this.mPresenter = presenter;
}
@Override
public void refresh(final List<StoriesEntity> list) {
mAdapter.setNewsList(list);
mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent intent = new Intent(getActivity(), StoryDetailActivity.class);
intent.putExtra(StoryDetailFragment.STORY_ID, list.get(position).getId());
intent.putExtra(StoryDetailFragment.STORY_TITLE, list.get(position).getTitle());
startActivity(intent);
}
});
}
@Override
public void setTitle() {
if (mActionBar != null) {
mActionBar.setTitle(R.string.app_name);
}
}
}
model
因为这里没有考虑到数据的持久化，没有创建本地数据库，所以，model的实现其实就是一个service，因为是用reftrofit2来完成网络请求的，所以，model就是ZhiHuService.java：
public interface ZhiHuService {
//今日头条
@GET("/api/4/news/latest")
Observable<RootEntity> getLatestNews();
//互联网安全
@GET("/api/4/theme/10")
Observable<RootEntity> getSafety();
//不准无聊
@GET("/api/4/theme/11")
Observable<RootEntity> getInterest();
//体育日报
@GET("/api/4/theme/8")
Observable<RootEntity> getSport();
}
avtivity
最后看看activity，作用有三个：创建view（这里是views）、创建presenter、管理fragemnt：
public class MainActivity extends AppCompatActivity {
@BindView(R.id.tab_item_main_0)
TabItem tabItemMain0;
@BindView(R.id.tab_item_main_1)
TabItem tabItemMain1;
@BindView(R.id.tab_item_main_2)
TabItem tabItemMain2;
@BindView(R.id.tab_item_main_3)
TabItem tabItemMain3;
@BindView(R.id.tab_item_main_4)
TabItem tabItemMain4;
@BindView(R.id.toolbar)
Toolbar toolbar;
@BindView(R.id.fab)
FloatingActionButton floatingBar;
private FragmentManager mFragmentManager;
private TodayFragment mTodayFragment;
private InterestFragment mInterestFragment;
private SafetyFragment mSafetyFragment;
private SportFragment mSportFragment;
private OtherFragment mOtherFragment;
private MainPresenter mPresenter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ButterKnife.bind(this);
mFragmentManager = getSupportFragmentManager();
setSupportActionBar(toolbar);
mPresenter = new MainPresenter(getApplicationContext());
tabItemMain0.performClick();
}
public void showFragment(int tag) {
if (mFragmentManager != null) {
FragmentTransaction transaction = mFragmentManager.beginTransaction();
hideFragments();
switch (tag) {
case TagStatic.TAG_FRAGMENT_TODAY:
mTodayFragment = (TodayFragment) mFragmentManager.findFragmentByTag(TagStatic.TAG_FRAGMENT_TODAY + "");
if (mTodayFragment == null) {
mTodayFragment = new TodayFragment();
transaction.add(R.id.fragment_content, mTodayFragment, tag + "");
} else {
transaction.show(mTodayFragment);
}
mPresenter.setView(mTodayFragment);
break;
case TagStatic.TAG_FRAGMENT_INTEREST:
mInterestFragment = (InterestFragment) mFragmentManager.findFragmentByTag(TagStatic.TAG_FRAGMENT_INTEREST + "");
if (mInterestFragment == null) {
mInterestFragment = new InterestFragment();
transaction.add(R.id.fragment_content, mInterestFragment, tag + "");
} else {
transaction.show(mInterestFragment);
}
mPresenter.setView(mInterestFragment);
break;
case TagStatic.TAG_FRAGMENT_SAFETY:
mSafetyFragment = (SafetyFragment) mFragmentManager.findFragmentByTag(TagStatic.TAG_FRAGMENT_SAFETY + "");
if (mSafetyFragment == null) {
mSafetyFragment = new SafetyFragment();
transaction.add(R.id.fragment_content, mSafetyFragment, tag + "");
} else {
transaction.show(mSafetyFragment);
}
mPresenter.setView(mSafetyFragment);
break;
case TagStatic.TAG_FRAGMENT_SPORT:
mSportFragment = (SportFragment) mFragmentManager.findFragmentByTag(TagStatic.TAG_FRAGMENT_SPORT + "");
if (mSportFragment == null) {
mSportFragment = new SportFragment();
transaction.add(R.id.fragment_content, mSportFragment, tag + "");
} else {
transaction.show(mSportFragment);
}
mPresenter.setView(mSportFragment);
break;
case TagStatic.TAG_FRAGMENT_OTHER:
mOtherFragment = (OtherFragment) mFragmentManager.findFragmentByTag(TagStatic.TAG_FRAGMENT_OTHER + "");
if (mOtherFragment == null) {
mOtherFragment = new OtherFragment();
transaction.add(R.id.fragment_content, mOtherFragment, tag + "");
} else {
transaction.show(mOtherFragment);
}
mPresenter.setView(mOtherFragment);
break;
}
transaction.commitAllowingStateLoss();
}
}
private void hideFragments() {
FragmentTransaction transaction = mFragmentManager.beginTransaction();
mTodayFragment = (TodayFragment) mFragmentManager.findFragmentByTag(TagStatic.TAG_FRAGMENT_TODAY + "");
if (mTodayFragment != null) {
transaction.hide(mTodayFragment);
}
mInterestFragment = (InterestFragment) mFragmentManager.findFragmentByTag(TagStatic.TAG_FRAGMENT_INTEREST + "");
if (mInterestFragment != null) {
transaction.hide(mInterestFragment);
}
mSafetyFragment = (SafetyFragment) mFragmentManager.findFragmentByTag(TagStatic.TAG_FRAGMENT_SAFETY + "");
if (mSafetyFragment != null) {
transaction.hide(mSafetyFragment);
}
mSportFragment = (SportFragment) mFragmentManager.findFragmentByTag(TagStatic.TAG_FRAGMENT_SPORT + "");
if (mSportFragment != null) {
transaction.hide(mSportFragment);
}
mOtherFragment = (OtherFragment) mFragmentManager.findFragmentByTag(TagStatic.TAG_FRAGMENT_OTHER + "");
if (mOtherFragment != null) {
transaction.hide(mOtherFragment);
}
transaction.commitAllowingStateLoss();
}
@OnClick({R.id.tab_item_main_0, R.id.tab_item_main_1, R.id.tab_item_main_2,
R.id.tab_item_main_3, R.id.tab_item_main_4, R.id.fab})
public void onClick(View view) {
clearChecked();
switch (view.getId()) {
case R.id.tab_item_main_0:
tabItemMain0.setChecked(true);
showFragment(TagStatic.TAG_FRAGMENT_TODAY);
break;
case R.id.tab_item_main_1:
tabItemMain1.setChecked(true);
showFragment(TagStatic.TAG_FRAGMENT_INTEREST);
break;
case R.id.tab_item_main_2:
tabItemMain2.setChecked(true);
showFragment(TagStatic.TAG_FRAGMENT_SAFETY);
break;
case R.id.tab_item_main_3:
tabItemMain3.setChecked(true);
showFragment(TagStatic.TAG_FRAGMENT_SPORT);
break;
case R.id.tab_item_main_4:
tabItemMain4.setChecked(true);
showFragment(TagStatic.TAG_FRAGMENT_OTHER);
break;
case R.id.fab:
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_SHORT)
.setAction("Action", null).show();
break;
}
}
private void clearChecked() {
tabItemMain0.setChecked(false);
tabItemMain1.setChecked(false);
tabItemMain2.setChecked(false);
tabItemMain3.setChecked(false);
tabItemMain4.setChecked(false);
}
}
avtivity里的内容还是比较少的，只是多了Fragment的显示和隐藏，没有变得复杂和职责不清，对于管理和维护也很简单。因为有多个view实现类，所以，我没有在presenter的初始化时传入view实例，而是通过在presenter中的setView方法设置不同的view。
跟retrofit2相关的内容这里不展开说，不知道的、想了解的可以自行搜索，这里是GitHub地址：retrofit，以及本文的项目源码：Login-MVP-Architecture ，希望对MVP感兴趣以及任何想要一起提高Android开发技能的小伙伴能star一下，以后会继续在这个项目上添加新的内容，包括一些有用的工具类、各种控件、效果实现、设计模式的使用等等。
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