Question

我有一个班级，通过匕首使用DI注入。但是，当活动被销毁并重新创建时，模型类似乎自动包含数据而不会插入/重新填充数据。

public class MyApplication extends Application {

    private ExpressionFactoryComponent mExpressionFactoryComponent;

    @Override
    public void onCreate() {
        super.onCreate();

        // Building dagger DI component
        mExpressionFactoryComponent = DaggerExpressionFactoryComponent.builder().
                expressionFactoryModule(new ExpressionFactoryModule(new ExpressionFactory(this))).build();
    }
}

模块：

@Module
public class ExpressionFactoryModule {
    private ExpressionFactory mExpressionFactory;

    public ExpressionFactoryModule(ExpressionFactory expressionFactory) {
        this.mExpressionFactory = expressionFactory;
    }

    @Provides
    ExpressionFactory provideStringExpressionFactory() {
        return mExpressionFactory;
    }
}

Answer 1

这样做的一个原因是ExpressionFactory在MyApplication类中实例化，然后在创建ExpressionFactoryModule时传递到ExpressionFactoryComponent的构造函数中。您应该在模块构造函数中传递Application实例，然后使用带有@Provide注释的metod创建类的实例，并在类的构造函数中传递Application实例。< / p>

这应该用匕首来完成。但是要解决您的问题，您需要创建另一个组件类并在活动中构建组件，如果您需要让您的类的实例仅与活动一起生成。

这是解决方案（ExpressionFactoryComponent在这里重命名为AppComponent）：

public class MyApplication extends Application {

    private static AppComponent appComponent;

    @Override
    public void onCreate() {
        super.onCreate();

        // Building dagger DI component
        appComponent = DaggerAppComponent.builder()
                .appModule(new AppModule(this)).build();
    }

    public static AppComponent getAppComponent() {
        return appComponent;
    }
}


@Component(modules = {AppModule.class})
public interface AppComponent {

    Application getApplication();

    void inject(App application);
}


@Module
public class AppModule {

    private Application application;

    public AppModule(Application application) {
        this.application = application;
    }


    @Provides
    Application provideApplication() {
        return application;
    }
}


@Component(dependencies = AppComponent.class, modules = {
        ActivityModule.class})
public interface ActivityComponent {

    void inject(MainActivity activity);

}

@Module
public class ActivityModule {

    private Activity activity;

    public ActivityModule(Activity activity) {
        this.activity = activity;
    }

    @Provides
    Activity provideActivity() {
        return activity;
    }


    @Provides
    ExpressionFactory provideStringExpressionFactory(Application application) {
        return new ExpressionFactory(application);
    }

}

public class MainActivity extends AppCompatActivity{


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ActivityComponent activityComponent = DaggerActivityComponent.builder()
                    .activityModule(new ActivityModule(activity))
                    .appComponent(App.getAppComponent())
                    .build();

        activityComponent.inject(this); 

    }

}

Dagger自动保存数据

1 个答案: