1.BasicSample - Shows how to persist data using a SQLite database and Room. Also uses ViewModels and LiveData.

此 sample 需求非常简单, 使用 list 展示(持久化)数据库中的数据, 点击每个 item 可以进入到详情页(展示详情信息)

1.1MainActivity.java -- main_activity.xml

作为一个 fragment 的载体, 仅仅包括一个 fragment: 1.2ProductListFragment.java
还有个 public method 展示ProductFragment.java(一会再来看)

1.2ProductListFragment.java -- list_fragment.xml

此界面中有2个 view, 一个是加载完成前的 loading 提示view, 一个是加载完成后的 recyclerView

1.2ProductListFragment 中使用了android.databinding 进行 fragment, xml 和数据的绑定
onCreateView() 中 init:

private ListFragmentBinding mBinding;
mBinding = DataBindingUtil.inflate(inflater, R.layout.list_fragment, container, false);

在 list_fragment.xml 中,
--1.使用<data> 标签,声明 var
--2.使用 app:visibleGone="@{isLoading}" 对 view 进行动态控制

<layout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>
        <variable
            name="isLoading"
            type="boolean" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/cardview_light_background"
        android:orientation="vertical">

        <TextView
            android:id="@+id/loading_tv"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:gravity="center_vertical|center_horizontal"
            android:text="@string/loading_products"
            android:textAlignment="center"
            app:visibleGone="@{isLoading}"
            />

        <android.support.v7.widget.RecyclerView
            android:id="@+id/products_list"
            android:contentDescription="@string/cd_products_list"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layoutManager="LinearLayoutManager"
            app:visibleGone="@{!isLoading}"/>

    </LinearLayout>
</layout>

--3.${visibleGone} 关键字在 BindingAdapters.java 中被自定义, 然后 showHide() 方法对 view 进行动态控制

public class BindingAdapters {
    @BindingAdapter("visibleGone")
    public static void showHide(View view, boolean show) {
        view.setVisibility(show ? View.VISIBLE : View.GONE);
    }
}

--4. 而 showHide() 是在ListFragmentBinding.java 中被调用, 是自动生成的

public class ListFragmentBinding extends android.databinding.ViewDataBinding  {
...
 com.example.android.persistence.ui.BindingAdapters.showHide(this.loadingTv, isLoading);
 com.example.android.persistence.ui.BindingAdapters.showHide(this.productsList, IsLoading1);
...
}

--5.适配器 ProductAdapter.java 对数据和 fragment 进行关联

 mProductAdapter = new ProductAdapter(mProductClickCallback);

--6.获取数据
在onActivityCreated() 中, 获取数据:

 final ProductListViewModel viewModel = ViewModelProviders.of(this).get(ProductListViewModel.class);
    
 // Update the list when the data changes        
 viewModel.getProducts().observe(this, new Observer<List<ProductEntity>>() {
            @Override
            public void onChanged(@Nullable List<ProductEntity> myProducts) {
                if (myProducts != null) {
                    mBinding.setIsLoading(false);
                    mProductAdapter.setProductList(myProducts);
                } else {
                    mBinding.setIsLoading(true);
                }
            }
        });

这段代码使用了新的方式获取数据库中的数据:ViewModelProviders.of(this).get(ProductListViewModel.class);
--7.ProductListViewModel.java
ViewModelProviders为arch 中的方法;
此处我们需要实现如下: 在 apply() 中有 loadAllProducts()的方法, 此方法实现在 Dao 中

public class ProductListViewModel extends AndroidViewModel {

    private static final MutableLiveData ABSENT = new MutableLiveData();
    {
        //noinspection unchecked
        ABSENT.setValue(null);
    }

    private final LiveData<List<ProductEntity>> mObservableProducts;

    public ProductListViewModel(Application application) {
        super(application);

        final DatabaseCreator databaseCreator = DatabaseCreator.getInstance(this.getApplication());

        LiveData<Boolean> databaseCreated = databaseCreator.isDatabaseCreated();
        mObservableProducts = Transformations.switchMap(databaseCreated,
                new Function<Boolean, LiveData<List<ProductEntity>>>() {
            @Override
            public LiveData<List<ProductEntity>> apply(Boolean isDbCreated) {
                if (!Boolean.TRUE.equals(isDbCreated)) { // Not needed here, but watch out for null
                    //noinspection unchecked
                    return ABSENT;
                } else {
                    //noinspection ConstantConditions
                    return databaseCreator.getDatabase().productDao().loadAllProducts();
                }
            }
        });

        databaseCreator.createDb(this.getApplication());
    }

    /**
     * Expose the LiveData Products query so the UI can observe it.
     */
    public LiveData<List<ProductEntity>> getProducts() {
        return mObservableProducts;
    }
}

--8.ProductEntity.java
@Entity 是 新的包 arch.room 中的
此类是Product 的实体类:
@Entity(tableName = "products"): 表名为"products"
@PrimaryKey private int id; : primary key 为 id

@Entity(tableName = "products")
public class ProductEntity implements Product {
    @PrimaryKey
    private int id;
    private String name;
    private String description;
    private int price;

    @Override
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    @Override
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    @Override
    public int getPrice() {
        return price;
    }

    public void setPrice(int price) {
        this.price = price;
    }

    public ProductEntity() {
    }

    public ProductEntity(Product product) {
        this.id = product.getId();
        this.name = product.getName();
        this.description = product.getDescription();
        this.price = product.getPrice();
    }
}

--9.ProductDao.java
@Dao 是新的包 arch.room 中的
形如 retrofit2的接口请求, 实现起来的方式和retrofit 很像

@Dao
public interface ProductDao {
    @Query("SELECT * FROM products") 
    LiveData<List<ProductEntity>> loadAllProducts();

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    void insertAll(List<ProductEntity> products);

    @Query("select * from products where id = :productId")
    LiveData<ProductEntity> loadProduct(int productId);

    @Query("select * from products where id = :productId")
    ProductEntity loadProductSync(int productId);
}

--10.上一张图简单理解下 View ViewModel model 的关系

final-architecture.png

2.GithubBrowserSample - An advanced sample that uses the Architecture components, Dagger and the Github API. Requires Android Studio 3.0 canary 1

--1.MainActivity.java
implements LifecycleRegistryOwner

    @Override
    public LifecycleRegistry getLifecycle() {
        return lifecycleRegistry;
    }

implements HasSupportFragmentInjector

 @Override
    public DispatchingAndroidInjector<Fragment> supportFragmentInjector() {
        return dispatchingAndroidInjector;
    }

通过注入NavigationController 控制 fragment

@Inject
    NavigationController navigationController;
    @Inject
    public NavigationController(MainActivity mainActivity) {
        this.containerId = R.id.container;
        this.fragmentManager = mainActivity.getSupportFragmentManager();
    }

    public void navigateToSearch() {
        SearchFragment searchFragment = new SearchFragment();
        fragmentManager.beginTransaction()
                .replace(containerId, searchFragment)
                .commitAllowingStateLoss();
    }

--2.SearchFragment.java
dataBinding

 <data>
        <import type="com.android.example.github.vo.Repo"/>
        <import type="java.util.List"/>
        <import type="com.android.example.github.vo.Status"/>
        <import type="com.android.example.github.vo.Resource"/>
        <variable name="resultCount" type="int"/>
        <variable name="query" type="String"/>
        <variable name="loadingMore" type="boolean"/>
        <variable name="searchResource" type="Resource"/>
        <variable name="callback" type="com.android.example.github.ui.common.RetryCallback"/>
    </data>

SearchFragmentBinding dataBinding = DataBindingUtil
                .inflate(inflater, R.layout.search_fragment, container, false,
                        dataBindingComponent);

extends LifecycleFragment

功能1:searching function:

    private void doSearch(View v) {
        //get query key word
        String query = binding.get().input.getText().toString();
        // Dismiss keyboard
        dismissKeyboard(v.getWindowToken());
        binding.get().setQuery(query);
        searchViewModel.setQuery(query);
    }

--3.SearchViewModel.java
extends ViewModel
功能1:refresh()

    void refresh() {
        if (query.getValue() != null) {
            query.setValue(query.getValue());
        }
    }

功能2:loadNextPage()

    void loadNextPage() {
        String value = query.getValue();
        if (value == null || value.trim().length() == 0) {
            return;
        }
        nextPageHandler.queryNextPage(value);
    }

--4.DAO @Dao
RepoDao.java
UserDao.java
--5.Entity @Entity
RepoEntity.java
UserEntity.java
RepoSearchResultEntity.java
ContributorEntity.java
--6.GithubService.java

    @GET("users/{login}")
    LiveData<ApiResponse<User>> getUser(@Path("login") String login);

    @GET("users/{login}/repos")
    LiveData<ApiResponse<List<Repo>>> getRepos(@Path("login") String login);

    @GET("repos/{owner}/{name}")
    LiveData<ApiResponse<Repo>> getRepo(@Path("owner") String owner, @Path("name") String name);

    @GET("repos/{owner}/{name}/contributors")
    LiveData<ApiResponse<List<Contributor>>> getContributors(@Path("owner") String owner, @Path("name") String name);

    @GET("search/repositories")
    LiveData<ApiResponse<RepoSearchResponse>> searchRepos(@Query("q") String query);

    @GET("search/repositories")
    Call<RepoSearchResponse> searchRepos(@Query("q") String query, @Query("page") int page);

--7.repository
RepoRepository.java

GithubDb db;
//操作数据库
RepoDao repoDao;
//网络操作
GithubService githubService;
AppExecutors appExecutors;

UserRepository.java

//操作数据库
UserDao userDao;
//网络操作
GithubService githubService;
AppExecutors appExecutors;

--8.AppComponent.java

@Singleton
@Component(modules = {
        AndroidInjectionModule.class,
        AppModule.class,
        MainActivityModule.class
})
public interface AppComponent {
    @Component.Builder
    interface Builder {
        @BindsInstance Builder application(Application application);
        AppComponent build();
    }
    void inject(GithubApp githubApp);
}

--9.AppModule.java

@Module(includes = ViewModelModule.class)

 @Singleton @Provides
    GithubService provideGithubService() {
        return new Retrofit.Builder()
                .baseUrl("https://api.github.com/")
                .addConverterFactory(GsonConverterFactory.create())
                .addCallAdapterFactory(new LiveDataCallAdapterFactory())
                .build()
                .create(GithubService.class);
    }

    @Singleton @Provides
    GithubDb provideDb(Application app) {
        return Room.databaseBuilder(app, GithubDb.class,"github.db").build();
    }

    @Singleton @Provides
    UserDao provideUserDao(GithubDb db) {
        return db.userDao();
    }

    @Singleton @Provides
    RepoDao provideRepoDao(GithubDb db) {
        return db.repoDao();
    }

--10.MainActivityModule.java

@ContributesAndroidInjector(modules = FragmentBuildersModule.class)
    abstract MainActivity contributeMainActivity();

--11.FragmentBuildersModule.java

    @ContributesAndroidInjector
    abstract RepoFragment contributeRepoFragment();

    @ContributesAndroidInjector
    abstract UserFragment contributeUserFragment();

    @ContributesAndroidInjector
    abstract SearchFragment contributeSearchFragment();