如何使用DI

@Inject

用来标记使用Dagger 实例化的类以及成员

@Component(modules = [])

用来绑定使用者与被使用者

@Module @Provides/@Binds

用来提供一些@Inject 不能自动创建实例的对象

普通的实例创建

public class Application{
    Car car = new Car();
}

DI 的声明

public class Application{
    @Inject Car car;
}
public class Car{
    @Inject
    public Car(){
    }
}
@Component
public interface CarComponent{
    void inject(Application app);
}

DI 使用：

public class Application{
public Application() {
        DaggerMainComponent.create().inject(this);
    }
}

Dagger.jpg

在使用Module的情况下类似
但是由于三方的依赖类无法在构造函数上添加@Inject注解
所以只能通过手动创建实例

@Component(modules = LiveDataModule.class)
public abstract class LiveDataComponent {
    void inject(DataViewModel dataViewModel){
        DataViewModel_MembersInjector.injectData(dataViewModel,new MutableLiveData<>());
    }
}

这一步与Dagger自动生成的类似

  @Override
  public void inject(Application app) {
    injectApplication(app);}
  
  private MainActivity injectMainActivity(MainActivity instance) {
    MainActivity_MembersInjector.injectCar(instance, new Car());
    MainActivity_MembersInjector.injectBlankFragment(instance, new BlankFragment());
    return instance;
  }

对于@Providers 与@Binds

//使用Binds 注解来提供方法
@Module 
public interface CarModule {
    @Binds public IEngine bindEngine(EngineImpl impl);
}
//使用Provides 注解来提供方法
@Module
public abstract class CarModule {
    @Provides
    public static IEngine provideEngine(EngineImpl impl){
        return impl;
    }
}

public class EngineImpl implements IEngine{
    @Inject public EngineImpl(){}
}

@Provides 注解生成的inject流程

  private IEngine getIEngine() {
    return CarModule_ProvideEngineFactory.provideEngine(new EngineImpl());}

  @Override
  public void inject(MainActivity activity) {
    injectMainActivity(activity);}

  private MainActivity injectMainActivity(MainActivity instance) {
    MainActivity_MembersInjector.injectEngine(instance, getIEngine());
    return instance;
  }

  public static IEngine provideEngine(EngineImpl impl) {
    return Preconditions.checkNotNull(CarModule.provideEngine(impl), "Cannot return null from a non-@Nullable @Provides method");
  }

@Binds 注解生成的inject流程

  @Override
  public void inject(MainActivity activity) {
    injectMainActivity(activity);}

  private MainActivity injectMainActivity(MainActivity instance) {
    MainActivity_MembersInjector.injectEngine(instance, new EngineImpl());
    return instance;
  }