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Sample 简介
一个简单的结合 Retrofit 和 RxJava 框架实现 MVVM 架构的例子。
最近在研究 Kotlin for Android，做了一个基于 Clean 架构以及 Retrofit ， RxKotlin ， Dagger 框架实现的 Kotlin for Android App ，更多详情请戳这里。
效果预览
sample.gif
准备知识
MVC
MVC
- 视图（View）：用户界面。
- 控制器（Controller）：业务逻辑
- 模型（Model）：数据保存
- View 传送指令到 Controller
- Controller 完成业务逻辑后，要求 Model 改变状态
- Model 将新的数据发送到 View，使用户得到反馈
缺陷:View 和 Model 是相互可知，耦合性大，像 Activity 或者 Fragment 既是 Controller 层，又是 View 层，造成工程的可扩展性可维护性非常差。
MVP
mvp.png
在 MVP 设计架构中，Controller 变成了 Presenter。
- 各层之间的通信，都是双向的。
- View 与 Model 不直接发生联系，都通过 Presenter 进行间接通信。
- Model 层与 Presenter 层，Presenter 层与 View 层之间通过接口建立联系。
采用 MVP 设计架构，Activity 与 Fragment 只位于 View 层。
MVP 的缺陷在于:由于我们使用了接口的方式去连接 View 层和 Presenter 层，这样就导致了一个问题，当你的页面逻辑很复杂的时候，你的接口会有很多，如果你的 app 中有很多个这样复杂的页面，维护接口的成本就会变的非常的大。
MVVM
MVVM
MVVM 模式将 Presenter 改名为 ViewModel，基本上与 MVP 模式完全一致。
区别在于: View 层与 ViewModel 层通过DataBinding相互绑定，View的变动，自动反映在 ViewModel，反之亦然。
RxJava
RxJava 在 GitHub 主页上的自我介绍是 "a library for composing asynchronous and event-based programs using observable sequences for the Java VM"（一个在 Java VM 上使用可观测的序列来组成异步的、基于事件的程序的库）。
RxJava 本质上是一个异步操作库，是一个能让你用极其简洁的逻辑去处理繁琐复杂任务的异步事件库。
简而言之，RxJava 可以用几个关键字概括：简洁，队列化，异步。
Retrofit
Retrofit
一个 Android 和 Java 上 HTTP 库（利用注解和 okhttp 来实现和服务器的数据交互）。
Retrofit 官方文档:http://square.github.io/retrofit/
DataBinding
DataBinding
在今年的 Google IO 2015 中，Google 在 support-v7 中新增了 Data Binding，使用 Data Binding 可以直接在布局的 xml 中绑定布局与数据，从而简化代码，Android Data Binding 是Android 的 MVVM 框架。因为 Data Binding 是包含在 support-v7 包里面的，所以可以向下兼容到最低 Android 2.1 (API level 7+).
实践
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直接上代码。
依赖的第三方类库
compile 'io.reactivex:rxjava:1.1.0'
compile 'io.reactivex:rxandroid:1.1.0'
compile 'com.squareup.retrofit2:retrofit:2.0.0-beta4'
compile 'com.squareup.retrofit2:converter-gson:2.0.0-beta4'
compile 'com.squareup.retrofit2:adapter-rxjava:2.0.0-beta4'
compile 'com.github.bumptech.glide:glide:3.7.0'
API
https://api.douban.com/v2/movie/top250?start=0&count=20
引入DataBinding
android {
......
dataBinding {
enabled = true
}
}
工程目录结构
工程目录结构
MVVM 之 View
MainActivity.java
getFragmentManager().beginTransaction().add(R.id.movie_fragment, MovieFragment.getInstance()).commit();
MovieFragment.java
public class MovieFragment extends Fragment implements CompletedListener,SwipeRefreshLayout.OnRefreshListener{
private static String TAG = MovieFragment.class.getSimpleName();
private MainViewModel viewModel;
private MovieFragmentBinding movieFragmentBinding;
private MovieAdapter movieAdapter;
public static MovieFragment getInstance() {
return new MovieFragment();
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View contentView = inflater.inflate(R.layout.movie_fragment, container, false);
movieFragmentBinding = MovieFragmentBinding.bind(contentView);
initData();
return contentView;
}
private void initData() {
movieAdapter = new MovieAdapter();
movieFragmentBinding.recyclerView.setLayoutManager(new LinearLayoutManager(getActivity(), LinearLayoutManager.VERTICAL, false));
movieFragmentBinding.recyclerView.setItemAnimator(new DefaultItemAnimator());
movieFragmentBinding.recyclerView.setAdapter(movieAdapter);
movieFragmentBinding.swipeRefreshLayout.setColorSchemeResources(R.color.colorAccent, R.color.colorPrimary, R.color.colorPrimaryDark);
movieFragmentBinding.swipeRefreshLayout.setOnRefreshListener(this);
viewModel = new MainViewModel(movieAdapter,this);
movieFragmentBinding.setViewModel(viewModel);
}
@Override
public void onRefresh() {
movieAdapter.clearItems();
viewModel.refreshData();
}
@Override
public void onCompleted() {
if (movieFragmentBinding.swipeRefreshLayout.isRefreshing()) {
movieFragmentBinding.swipeRefreshLayout.setRefreshing(false);
}
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context=".view.MainActivity">
<!-- ... -->
<FrameLayout
android:layout_marginTop="?attr/actionBarSize"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/movie_fragment"/>
<!-- ... -->
</android.support.design.widget.CoordinatorLayout>
movie_fragment.xml
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<data>
<variable
name="viewModel"
type="com.jc.mvvmrxjavaretrofitsample.viewModel.MainViewModel"/>
</data>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v4.widget.SwipeRefreshLayout
android:visibility="@{viewModel.contentViewVisibility}"
android:id="@+id/swipe_refresh_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_view"
android:background="#ddd"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="8dp">
</android.support.v7.widget.RecyclerView>
</android.support.v4.widget.SwipeRefreshLayout>
<ProgressBar
style="?android:attr/progressBarStyleLarge"
android:id="@+id/progress_bar"
android:visibility="@{viewModel.progressBarVisibility}"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"/>
<LinearLayout
android:layout_width="match_parent"
android:id="@+id/error_info_layout"
android:visibility="@{viewModel.errorInfoLayoutVisibility}"
android:orientation="vertical"
android:layout_height="match_parent">
<TextView
android:layout_gravity="center"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@{viewModel.exception}"/>
</LinearLayout>
</RelativeLayout>
</layout>
movie_item.xml
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/tools">
<data>
<variable
name="viewModel"
type="com.jc.mvvmrxjavaretrofitsample.viewModel.MovieViewModel"/>
</data>
<android.support.v7.widget.CardView
xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:id="@+id/card_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
card_view:cardCornerRadius="4dp"
card_view:cardBackgroundColor="@color/background"
card_view:cardUseCompatPadding="true">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<ImageView
android:layout_margin="8dp"
android:layout_width="60dp"
android:layout_height="100dp"
android:src="@drawable/cover"
app:imageUrl="@{viewModel.imageUrl}"
android:id="@+id/cover"/>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_margin="8dp"
android:orientation="vertical">
<TextView
android:textColor="@android:color/black"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@{viewModel.title}"
android:textSize="12sp"/>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="4dp"
android:orientation="horizontal">
<android.support.v7.widget.AppCompatRatingBar
android:id="@+id/ratingBar"
style="?android:attr/ratingBarStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_vertical"
android:isIndicator="true"
android:max="10"
android:numStars="5"
android:rating="@{viewModel.rating}" />
<TextView
android:id="@+id/rating_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_vertical"
android:layout_marginLeft="6dp"
android:text="@{viewModel.ratingText}"
android:textColor="?android:attr/textColorSecondary"
android:textSize="10sp" />
</LinearLayout>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="?android:attr/textColorSecondary"
android:textSize="10sp"
android:text="@{viewModel.movieType}"
android:id="@+id/movie_type_text"
android:layout_marginTop="6dp"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="?android:attr/textColorSecondary"
android:textSize="10sp"
android:text="@{viewModel.year}"
android:id="@+id/year_text"
android:layout_marginTop="6dp"
/>
</LinearLayout>
</LinearLayout>
</android.support.v7.widget.CardView>
</layout>
MovieAdapter.java
public class MovieAdapter extends RecyclerView.Adapter<MovieAdapter.BindingHolder> {
private List<Movie> movies;
public MovieAdapter() {
movies = new ArrayList<>();
}
@Override
public BindingHolder onCreateViewHolder(ViewGroup parent, int viewType) {
MovieItemBinding itemBinding = DataBindingUtil.inflate(LayoutInflater.from(parent.getContext()), R.layout.movie_item, parent, false);
return new BindingHolder(itemBinding);
}
@Override
public void onBindViewHolder(BindingHolder holder, int position) {
MovieViewModel movieViewModel = new MovieViewModel(movies.get(position));
holder.itemBinding.setViewModel(movieViewModel);
}
@Override
public int getItemCount() {
return movies.size();
}
public void addItem(Movie movie) {
movies.add(movie);
notifyItemInserted(movies.size() - 1);
}
public void clearItems() {
movies.clear();
notifyDataSetChanged();
}
public static class BindingHolder extends RecyclerView.ViewHolder {
private MovieItemBinding itemBinding;
public BindingHolder(MovieItemBinding itemBinding) {
super(itemBinding.cardView);
this.itemBinding = itemBinding;
}
}
}
回调接口** CompletedListener.java**
public interface CompletedListener {
void onCompleted();
}
MVVM 之 ViewModel
MainViewModel.java
public class MainViewModel {
public ObservableField<Integer> contentViewVisibility;
public ObservableField<Integer> progressBarVisibility;
public ObservableField<Integer> errorInfoLayoutVisibility;
public ObservableField<String> exception;
private Subscriber<Movie> subscriber;
private MovieAdapter movieAdapter;
private CompletedListener completedListener;
public MainViewModel(MovieAdapter movieAdapter,CompletedListener completedListener) {
this.movieAdapter = movieAdapter;
this.completedListener = completedListener;
initData();
getMovies();
}
private void getMovies() {
subscriber = new Subscriber<Movie>() {
@Override
public void onCompleted() {
Log.d("[MainViewModel]", "onCompleted");
hideAll();
contentViewVisibility.set(View.VISIBLE);
completedListener.onCompleted();
}
@Override
public void onError(Throwable e) {
hideAll();
errorInfoLayoutVisibility.set(View.VISIBLE);
exception.set(e.getMessage());
}
@Override
public void onNext(Movie movie) {
movieAdapter.addItem(movie);
}
};
RetrofitHelper.getInstance().getMovies(subscriber, 0, 20);
}
public void refreshData() {
getMovies();
}
private void initData() {
contentViewVisibility = new ObservableField<>();
progressBarVisibility = new ObservableField<>();
errorInfoLayoutVisibility = new ObservableField<>();
exception = new ObservableField<>();
contentViewVisibility.set(View.GONE);
errorInfoLayoutVisibility.set(View.GONE);
progressBarVisibility.set(View.VISIBLE);
}
private void hideAll(){
contentViewVisibility.set(View.GONE);
errorInfoLayoutVisibility.set(View.GONE);
progressBarVisibility.set(View.GONE);
}
}
MovieViewModel.java
public class MovieViewModel extends BaseObservable {
private Movie movie;
public MovieViewModel(Movie movie) {
this.movie = movie;
}
public String getCoverUrl() {
return movie.getImages().getSmall();
}
public String getTitle() {
return movie.getTitle();
}
public float getRating() {
return movie.getRating().getAverage();
}
public String getRatingText(){
return String.valueOf(movie.getRating().getAverage());
}
public String getYear() {
return movie.getYear();
}
public String getMovieType() {
StringBuilder builder = new StringBuilder();
for (String s : movie.getGenres()) {
builder.append(s + " ");
}
return builder.toString();
}
public String getImageUrl() {
return movie.getImages().getSmall();
}
@BindingAdapter({"app:imageUrl"})
public static void loadImage(ImageView imageView,String url) {
Glide.with(imageView.getContext())
.load(url)
.placeholder(R.drawable.cover)
.error(R.drawable.cover)
.into(imageView);
}
}
MVVM 之 Model
DouBanMovieService.java
public interface DouBanMovieService {
String BASE_URL = "https://api.douban.com/v2/movie/";
@GET("top250")
Observable<Response<List<Movie>>> getMovies(@Query("start") int start, @Query("count") int count);
}
RetrofitHelper.java
public class RetrofitHelper {
private static final int DEFAULT_TIMEOUT = 10;
private Retrofit retrofit;
private DouBanMovieService movieService;
OkHttpClient.Builder builder;
/**
* 获取RetrofitHelper对象的单例
* */
private static class Singleton {
private static final RetrofitHelper INSTANCE = new RetrofitHelper();
}
public static RetrofitHelper getInstance() {
return Singleton.INSTANCE;
}
public RetrofitHelper() {
builder = new OkHttpClient.Builder();
builder.connectTimeout(DEFAULT_TIMEOUT, TimeUnit.SECONDS);
retrofit = new Retrofit.Builder()
.client(builder.build())
.addConverterFactory(GsonConverterFactory.create())
.addCallAdapterFactory(RxJavaCallAdapterFactory.create())
.baseUrl(DouBanMovieService.BASE_URL)
.build();
movieService = retrofit.create(DouBanMovieService.class);
}
public void getMovies(Subscriber<Movie> subscriber, int start, int count) {
movieService.getMovies(start, count)
.map(new Func1<Response<List<Movie>>, List<Movie>>() {
@Override
public List<Movie> call(Response<List<Movie>> listResponse) {
return listResponse.getSubjects();
}
})
.flatMap(new Func1<List<Movie>, Observable<Movie>>() {
@Override
public Observable<Movie> call(List<Movie> movies) {
return Observable.from(movies);
}
})
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(subscriber);
}
}
还有 entity 类，这里就不贴出来了。
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