如何使用Dagger2将演示者插入片段？

Question

我有RegisterPresenterImpl，我想注入片段。当我调用演示者的方法register（）时，我的应用程序崩溃。它说我的演示者为null。

我该如何解决这个问题？

public class RegisterAccountFragment extends Fragment implements RegisterAccountView { 


@Inject 
RegisterAccountPresenterImpl registerPresenter; 

public RegisterAccountFragment() { 
    // Required empty public constructor 
} 


@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
         Bundle savedInstanceState) { 
    // Inflate the layout for this fragment 
    View v = inflater.inflate(R.layout.fragment_register_account, container, false); 

DaggerRegisterAccountComponent.builder() 
      .netComponent(((App) getActivity().getApplicationContext()).getNetComponent()) 
      .registerAccountModule(new RegisterAccountModule(this)) 
      .build() 
      .inject(this); 

    registerPresenter.register(getName(), getEmail(), getPassword(), getConfirm()); 
    } 
} 

组件接口：

@FragmentScoped 
@Component(dependencies = NetComponent.class, modules = RegisterAccountModule.class) 
    public interface RegisterAccountComponent { 
     void inject(RegisterAccountFragment fragment); 
} 

这里是模块类：

@Module 
public class RegisterAccountModule { 

private RegisterAccountView view; 

public RegisterAccountModule(RegisterAccountView view){ 
    this.view = view; 
} 


@Provides 
@FragmentScoped 
RegisterAccountView providesRegisterAccountView(){ 
    return view; 
    } 
} 

这里是称为RegisterPresenterImpl

public class RegisterAccountPresenterImpl implements RegisterAccountPresenter{ 

private RegisterAccountView view; 
private Retrofit retrofit; 
private CompositeDisposable compositeDisposable = new CompositeDisposable(); 

@Inject 
public RegisterAccountPresenterImpl(Retrofit retrofit, RegisterAccountView view){ 
    this.retrofit = retrofit; 
    this.view = view; 
} 

@Override 
public void register(String name, String email, String password, String confirm) { 
    // CODE 
    } 
} 

类

Answer 1

提供您RegisterAccountPresenterImpl在RegisterAccountComponent

它应该是这样的：

@FragmentScoped 
@Component(dependencies = NetComponent.class, modules = 
RegisterAccountModule.class) 
public interface RegisterAccountComponent { 
    void inject(RegisterAccountFragment fragment); 

    RegisterAccountPresenterImpl getRegisterAccountPresenterImlp(); 
} 

也有一些是你实现

1. Inject Constructor/Field/Method不支持public呢。在onCreate()而不是onCreateView()删除多余的关键字
2. 初始化你DaggerRegisterAccountComponent，以确保它会使用任何依赖年前建成。
3. 考虑使用final在RegisterAccountPresenterImpl所有field被设置内部构造。因为它只会初始化一次。

private final RegisterAccountView view; 

private final Retrofit retrofit; 

我只是不明白，为什么你必须定义一个view（这是你的片段）一presenter，反之亦然内。这是一个循环依赖？

我发现这个tutorial是关于使用MVP和Dagger的超酷贴。请考虑阅读

还有一件事：如果您想有效地调试Dagger-2，请转到您的Dagger...Component类，以查看其中内置的内容。 Android Studio将帮助您在使用时发现任何问题。

希望得到这个帮助！

Answer 2

应该

public class RegisterAccountFragment extends Fragment implements RegisterAccountView {  
    @Inject 
    RegisterAccountPresenter registerPresenter; // <-- not impl, why use DI then? 

而且

@FragmentScoped // <-- scope here 
public class RegisterAccountPresenterImpl implements RegisterAccountPresenter{ 

    private final RegisterAccountView view; 
    private final Retrofit retrofit; 

    @Inject 
    public RegisterAccountPresenterImpl(Retrofit retrofit, RegisterAccountView view){ 
     this.retrofit = retrofit; 
     this.view = view; 
    } 
} 

而且

@Module 
public class RegisterAccountModule { 

    private RegisterAccountView view; 

    public RegisterAccountModule(RegisterAccountView view){ 
     this.view = view; 
    } 

    @Provides 
    // @FragmentScoped // <-- no need for scoping item in module 
    RegisterAccountView providesRegisterAccountView(){ 
     return view; 
    } 

    @Provides // <-- provide constructor injected stuff and bind to interface 
    RegisterAccountPresenter registerAccountPresenter(RegisterAccountPresenterImpl impl) { 
     return impl; 
    } 
}