[英]Dao is null while using Dagger2
When i call DAO in presenter, it returns null and causes NPE.当我在演示者中调用 DAO 时,它返回 null 并导致 NPE。 Some code here: DAO class
这里有一些代码:DAO class
@Dao
public interface ElementsDao {
@Query("SELECT * FROM `elements`")
Flowable<List<Elements>> getAll();
@Insert
Maybe<Long> insert(Elements element);...
}
modules classes:模块类:
@Module
public class DatabaseModule {
private AppDatabase appDatabase;
public DatabaseModule(Application mApplication){
appDatabase = Room.databaseBuilder(mApplication, AppDatabase.class,"dbWarehouse")
.setJournalMode(RoomDatabase.JournalMode.TRUNCATE)
.build();
}
@Singleton
@Provides
public AppDatabase provideDatabase(){
return appDatabase;
}
@Singleton
@Provides
ElementsDao providesElementsDao(AppDatabase appDatabase){
return appDatabase.getElementsDao();
}
}
@Module
public class AppModule {
Application mApplication;
public AppModule(Application application){
mApplication = application;
}
@Provides
@Singleton
Application providesApplication() {
return mApplication;
}
}
Component class组件 class
@Singleton
@Component(dependencies = {},modules = {AppModule.class, DatabaseModule.class})
public interface AppComponent {
void inject(MainActivity mainActivity);
void inject(ElementsActivity elementsActivity);
void inject(ActivityElementsPresenter activityElementsPresenter);
ElementsDao elementsDao();
AppDatabase appDatabase();
Application application();
}
App class (declared in manifest)应用 class(在清单中声明)
public class App extends Application {
private static AppComponent appComponent;
@Override
public void onCreate() {
super.onCreate();
initDagger();
}
private void initDagger(){
appComponent = DaggerAppComponent.builder()
.appModule(new AppModule(this))
.databaseModule(new DatabaseModule(this))
.build();
}
public static AppComponent getAppComponent() {
return appComponent;
}
}
And presenter和主持人
@InjectViewState
public class ActivityElementsPresenter extends MvpPresenter<ActivityElementsView> {
@Inject
ElementsDao elementsDao;
public void addElement(Elements element){
elementsDao.insert(element).subscribeOn(Schedulers.io())...
UPDATE AppDatabase class更新应用数据库 class
@Database(entities = {Elements.class}, version = 1, exportSchema = false)
@TypeConverters({Converters.class})
public abstract class AppDatabase extends RoomDatabase {
public abstract ElementsDao getElementsDao();
//...
}
While debuging i setted a point in presenter and saw that dao isn't initialized elementsDao Trying to use something like App.getAppComponent().elementsDao();
在调试时,我在演示者中设置了一个点,发现 dao 没有初始化elementsDao尝试使用类似
App.getAppComponent().elementsDao();
but it inst works too.但它也可以工作。
You need to do it this way,你需要这样做,
@InjectViewState
public class ActivityElementsPresenter extends MvpPresenter<ActivityElementsView> {
@Inject
ElementsDao elementsDao;
public ActivityElementsPresenter(){
App.getAppComponent().inject(this);//calling the dagger's injector to inject dependency.
}
public void addElement(Elements element){
elementsDao.insert(element).subscribeOn(Schedulers.io())...
}
}
Then in然后在
@Singleton
@Component(dependencies = {},modules = {AppModule.class, DatabaseModule.class})
public interface AppComponent {
void inject(MainActivity mainActivity);
void inject(ElementsActivity elementsActivity);
void inject(ActivityElementsPresenter activityElementsPresenter);//will inject dependency to ActivityElementsPresenter.
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.