内容简介:Android Architecture Componets
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 @Singleton public 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
@Entity class User { @PrimaryKey private int id; private String name; private String lastName; // getters and setters for fields }
Dao
@Dao public 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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