比较 BasicSample 和 BasicRxJavaSample和PersistenceContentProviderSample

1.表格

	实现方式	BasicSample	BasicSample	PersistenceContentProviderSample
对应某个表的增删改查	Dao	@Dao 使用注解的方式实现 CRUD(接口类似 retrofit)	ProductDao	UserDao	CheeseDao
对应某个表的字段实体	Entity	@Entity(tableName = "${tbName}")	ProductEntity	UserEntity	CheeseEntity
绑定数据库和表	Database	@Database(entities = {${*Entity.class}}, version = 1) ~ extends RoomDatabase	AppDatabase	UsersDatabase	SampleDatabase
对数据库初始化,绑定关系	ViewModel	extends ViewModel(AndroidViewModel)	ProductListViewModel	UserViewModel
得到 ViewModel 的实例	Provider.Factory~extends ViewModelProvider.NewInstanceFactory	implements ViewModelProvider.Factory	ProductViewModel.Factory	ViewModelFactory
ContentProvider	extends ContentProvider	无	无	SampleContentProvider
主 View	Activity	extends LifecycleActivity	MainActivity	UserActivity
Injection	provideViewModelFactory	无	Injection
RxJava	使用mDisposable对数据库进行操作	无	UserActivity
绑定数据	DataBinding	在 xml 使用标签绑定 model	comment_item.xml	无

view 中获取数据

final ProductListViewModel viewModel =
               ViewModelProviders.of(this).get(ProductListViewModel.class);

       viewModel.getProducts().observe(this, new Observer>() {
            @Override
            public void onChanged(@Nullable List myProducts) {
                if (myProducts != null) {
                    mBinding.setIsLoading(false);
                    mProductAdapter.setProductList(myProducts);
                } else {
                    mBinding.setIsLoading(true);
                }
            }
        });

//BasicRxJavaSample:
//得到 ViewModelFactory
public static ViewModelFactory provideViewModelFactory(Context context) {
        UserDataSource dataSource = provideUserDataSource(context);
        return new ViewModelFactory(dataSource);
}

//得到 factory 实例
mViewModelFactory = Injection.provideViewModelFactory(this);

//使用ViewModelProviders获取 viewModel 实例
mViewModel = ViewModelProviders.of(this, mViewModelFactory).get(UserViewModel.class);

//使用 RxJava 读取数据库
  mDisposable.add(mViewModel.getUserName()
        .subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe(new Consumer() {
          @Override
          public void accept(String userName) throws Exception {
            mUserName.setText(userName);
          }
        }, new Consumer() {
          @Override
          public void accept(Throwable throwable) throws Exception {
            Log.e(TAG, "Unable to update username", throwable);
          }
        }));