java - Android Dagger2 2.11 unscoped Appcomponent reference scoped bindings

Question

我使用 https://medium.com/@iammert/new-android-injector-with-dagger-2-part-1-8baa60152abe 的 dagger2 演示.我已将 SharedPreferences 添加到我的 AppModule.java

@Module(subcomponents = {
    MainActivityComponent.class,
    DetailActivityComponent.class,
    Detail2ActivityComponent.class})
public class AppModule {

@Provides
@Singleton
Context provideContext(Application application) {
    return application;
    }

@Provides
@Singleton //if i remove dagger works right
SharedPreferences providesSharedPreferences(Application application) {
    return PreferenceManager.getDefaultSharedPreferences(application);
    }

}

我在 MainActivity 中注入(inject) SharedPreferences。重建项目后我得到错误

如果我通过 providesSharedPreferences 删除注释 @Singleton，则项目重建正确。 为什么 providesSharedPreferences 会出现问题 @Singleton 注解？

Answer 1

您需要将@Singleton 添加到AppComponent 类:

    @Singleton // <---- Add this line
    @Component(modules = {
        AndroidInjectionModule.class,
        AppModule.class,
        ActivityBuilder.class})
    public interface AppComponent {

        @Component.Builder
        interface Builder {
          @BindsInstance Builder application(Application application);
          AppComponent build();
        }

        void inject(AndroidSampleApp app);
    }