Android Architecture Componets

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Android Architecture Componets(Google官方提供的架构组件)

官网

https://developer.android.google.cn/topic/libraries/architecture/index.html

前言

Google 一直没有给Android 创建属于自己的官方架构方案，也没有官方确切的说支持MVP或者MVVM，反正什么样的架构代码的方式，Google一直都是包容的态度，在Github上也一直都有一个Android架构方案的开源项目。

https://github.com/googlesamples/android-architecture

2017 Google IO 虽然没有刻意去讨论Android，但是在Android Developer 网站上悄然出现了关于Android Architecture的东西，但并不是官方的架构方案，而是给出了一个可选的架构方案。

架构方案

Android Architecture Componets 组件

组件说明 url Lifecycle 有点像RxLifecycler的处理方式，监听生命周期中的事件 https://developer.android.google.cn/topic/libraries/architecture/lifecycle.html LiveData 使用观察者模式，用于观察数据返回，用过RxJava的都会觉得眼熟，可以替代部分RxJava的功能 https://developer.android.google.cn/topic/libraries/architecture/livedata.html ViewModel 在架构方案中，用于实现ViewModel层，同时默认绑定Lifecycle，生命周期可以使用Lifcycle中的生命回调来控制，可以脱离Activity或Fragment，在ViewModel中处理响应UI生命周期函数。 https://developer.android.google.cn/topic/libraries/architecture/viewmodel.html Room 官方 Sqlite ORM库 https://developer.android.google.cn/topic/libraries/architecture/room.html

架构方案代码演示

ViewModel demo

//继承ViewModel 在新推荐的架构方案中与Ui层进行逻辑分离public class UserProfileViewModel extends ViewModel {    private String userId;    private LiveData<User> user;    public void init(String userId) {        this.userId = userId;    }  //使用 LiveData 包装 真实的Model对象    public LiveData<User> getUser() {        return user;    }}

UI 层使用 ViewModel

//需要继承新的LifecycleFragment类，该类是Fragment的子类，但是该类实现了LifecycleOwner接口public class UserProfileFragment extends LifecycleFragment {    private static final String UID_KEY = "uid";    private UserProfileViewModel viewModel;    @Override    public void onActivityCreated(@Nullable Bundle savedInstanceState) {        super.onActivityCreated(savedInstanceState);        String userId = getArguments().getString(UID_KEY);      //获取ViweModel        viewModel = ViewModelProviders.of(this).get(UserProfileViewModel.class);      //滴啊用ViewModel中的业务方法        viewModel.init(userId);      //使用LiveData方式获取User信息        viewModel.getUser().observe(this, user -> {      // update UI        });    }    @Override    public View onCreateView(LayoutInflater inflater,                @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {        return inflater.inflate(R.layout.user_profile, container, false);    }}

Repository

//User Dagger2 DI@Singletonpublic class UserRepository {    private final Webservice webservice;    private final UserDao userDao;    private final Executor executor;    @Inject    public UserRepository(Webservice webservice, UserDao userDao, Executor executor) {        this.webservice = webservice;        this.userDao = userDao;        this.executor = executor;    }    public LiveData<User> getUser(String userId) {        refreshUser(userId);        // return a LiveData directly from the database.        return userDao.load(userId);    }    private void refreshUser(final String userId) {        executor.execute(() -> {            // running in a background thread            // check if user was fetched recently            boolean userExists = userDao.hasUser(FRESH_TIMEOUT);            if (!userExists) {                // refresh the data                Response response = webservice.getUser(userId).execute();                // TODO check for error etc.                // Update the database.The LiveData will automatically refresh so                // we don't need to do anything else here besides updating the database                userDao.save(response.body());            }        });    }}

WebService

//Retrofit 2 网络请求public interface Webservice {    /**     * @GET declares an HTTP GET request     * @Path("user") annotation on the userId parameter marks it as a     * replacement for the {user} placeholder in the @GET path     */    @GET("/users/{user}")    Call<User> getUser(@Path("user") String userId);}

Room 持久化数据

Entity

@Entityclass User {  @PrimaryKey  private int id;  private String name;  private String lastName;  // getters and setters for fields}

Dao

@Daopublic interface UserDao {    @Insert(onConflict = REPLACE)    void save(User user);    @Query("SELECT * FROM user WHERE id = :userId")    LiveData<User> load(String userId);}

RoomDatabase

@Database(entities = {User.class}, version = 1)public abstract class MyDatabase extends RoomDatabase {    public abstract UserDao userDao();}

依赖

项目根路径下的build.gradle 新增一下仓库

allprojects {    repositories {        jcenter()        maven { url 'https://maven.google.com' }    }}

依赖

//For Lifecycles, LiveData, and ViewModel, add:compile "android.arch.lifecycle:runtime:1.0.0-alpha1"compile "android.arch.lifecycle:extensions:1.0.0-alpha1"annotationProcessor "android.arch.lifecycle:compiler:1.0.0-alpha1"//For Room, add:compile "android.arch.persistence.room:runtime:1.0.0-alpha1"annotationProcessor "android.arch.persistence.room:compiler:1.0.0-alpha1"

已知限制和问题

测试版本的 Lifecycle Fragment 和ActivityCompat 在Support Library 中并没有实现LifecycleOwner 接口，在正式版1.0.0发布时，将正确实现。

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