I'm trying to learn dagger 2 but I'm confused in injecting of constructor with interface. This is my below code :
MainActivity.java
public class MainActivity extends AppCompatActivity implements MainView {
// this keyword of request dependency . At compiling process, dagger will look at all of these annotations
//to create the exact dependency
@Inject MainPresenter mainPresenter ;
TextView textView ;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textView = findViewById(R.id.textview) ;
DaggerPresenterComponent.create().inject(this);
textView.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view) {
mainPresenter.doThings(8555) ;
}
});
}
/**********************************/
@Override
public void invokeRandomViewMethod(String msg) {
textView.setText(msg);
}
}
MainPresenter.java
public class MainPresenter {
private MainView mainView ;
@Inject
public MainPresenter(MainView mainView) {
this.mainView = mainView;
}
public void doThings(int value){
Random random = new Random();
int rand= random.nextInt(value) ;
if(mainView != null){
mainView.invokeRandomViewMethod("You random number is "+rand);
}
}
public interface MainView {
void invokeRandomViewMethod(String msg) ;
}
}
This is the Module :
@Module
public class PresenterModule {
@Provides
// this is the method that will provide the dependancy
MainPresenter provideMainPresenter(MainView mainView){
return new MainPresenter(mainView);
}
}
And this is the Component
@Component (modules = PresenterModule.class)
public interface PresenterComponent {
void inject(MainActivity activity) ;
}
When I run the code it shows me this error :
Error:(15, 10) error: com.imennmn.hellodagger2example.MainView cannot be provided without an @Provides-annotated method. com.imennmn.hellodagger2example.MainView is injected at com.imennmn.hellodagger2example.presenterInjection.PresenterModule.provideMainPresenter(mainView) com.imennmn.hellodagger2example.MainPresenter is injected at com.imennmn.hellodagger2example.MainActivity.mainPresenter com.imennmn.hellodagger2example.MainActivity is injected at com.imennmn.hellodagger2example.simpleInjection.DataComponent.inject(activity)
My Question is how I can provide the interface MainView by inject it with dagger and bind the MainPresenter and MainActivity ? Any help would be appreciated !
By following code:
MainPresenter provideMainPresenter(MainView mainView) {
return new MainPresenter(mainView);
}
You are telling dagger: "hey, whenever I ask you to inject MainPresenter, construct it using MainView".
But dagger complaints, because you haven't specified how exactly he should build/acquire MainView.
So, in your PresenterModule do this:
@Module
public class PresenterModule {
MainView mainView;
public PresenterModule(MainView mainView) {
this.mainView = mainView;
}
@Provides
MainPresenter provideMainPresenter() {
return new MainPresenter(mainView);
}
}
Then when building the component:
DaggerPresenterComponent.builder()
.presenterModule(new PresenterModule(this))
.build();