java - 如果没有 @Inject 构造函数，则无法提供 Dagger2

Question

//模块

@Module
public class PresenterModule {

    @Provides
    @PerActivity
    public MainPresenter provideMainPresenter() {
        return new MainPresenter();
    }

    @Provides
    @PerActivity
    public PreLoginPresenter providePreLoginPresenter() {
        return new PreLoginPresenter();
    }

    @Provides
    @PerActivity
    public NotificationPresenter provideNotificationPresenter() {
        return new NotificationPresenter();
    }
}

@Module
public class UserLoginModule {

    @Provides
    @PerActivity
    public UserModel getUser(){
        return new UserModel();
    }
}

//组件

@PerActivity
@Component(modules = {UserLoginModule.class})
public interface UserLoginComponent {

    void injectSharedPreferences(SharedPreferences sharedPreferences);
    void injectPreLoginPresenter(PreLoginActivity preLoginActivity);
}

@PerActivity
@Component(modules = {PresenterModule.class})
public interface PresenterComponent {

    //void injectMainPresenter(MainActivity mainActivity);
    void injectPreLoginPresenter(PreLoginActivity preLoginActivity);
    //void injectNotificationPresenter(NotificationActivity notificationActivity);

}

` //PRELOGINPRESENTER

public class PreLoginPresenter {

@Inject
UserModel userModel;

public String onStateSelected(String state) {
        userModel.setState(state);
        return userModel.getState();
 }

 }

//登录前 Activity `

//ONCREATE内部

//Instantiate dagger 2
                 PresenterComponent presenterComponent =                        DaggerPresenterComponent.builder()
                .build();
              presenterComponent.injectPreLoginPresenter(PreLoginActivity.this);//passar o contexto para o componente

    //Instantiate dagger 2
        UserLoginComponent userLoginComponent = DaggerUserLoginComponent.builder()
            .build();
        userLoginComponent.injectPreLoginPresenter(PreLoginActivity.this);//passar o contexto para o componente``

//错误日志

Error:(18, 53) error: cannot find symbol class DaggerPresenterComponent Error:(19, 53) error: cannot find symbol class DaggerUserLoginComponent Error:(19, 10) error: gorick.gradesprojectandroid.MVP.Presenter.Presenters.PreLoginPresenter cannot be provided without an @Inject constructor or from an @Provides- or @Produces-annotated method. This type supports members injection but cannot be implicitly provided. gorick.gradesprojectandroid.MVP.Presenter.Presenters.PreLoginPresenter is injected at gorick.gradesprojectandroid.MVP.View.PreLoginActivity.preLoginPresenter gorick.gradesprojectandroid.MVP.View.PreLoginActivity is injected at gorick.gradesprojectandroid.Dagger2.Component.UserLoginComponent.injectPreLoginPresenter(preLoginActivity)

Answer 1

您已将 PreLoginPresenter 绑定(bind)到 PresenterModule 中，但尚未将其安装到 UserLoginComponent 中。这意味着您的 UserLoginComponent 没有将 PreLoginPresenter 注入(inject) PreLoginActivity 所需的绑定(bind)，因此代码生成失败，并给出错误消息。

您不需要用两个不同的组件注入(inject)同一个类；无法表达一个组件满足某些绑定(bind)而另一个组件满足其他绑定(bind)。相反，请确保您有一个涵盖所有内容的组件，然后使用该组件进行注入(inject)。