Mortar and Flow libraries vs. ViewPager

Question

I'm trying to adapt Mortar&Flow in my app and faced with an issue, that I can't make PageAdapter works with Screens, instead of Fragments.

Anyone managed to get it right?

I didn't succeed but, probably someone can guide me from this point:

The initial Dagger Registration:

@Module(
    injects = {
            MainActivity.class,
    },
    library = true,
    complete = false
)
public class DaggerConfig {
    @SuppressWarnings("unused")
    @Provides @Singleton Gson provideGson() {
        return new GsonBuilder().create();
    }
}

MainScreen, whose View is hosting ViewPager:

@Layout(R.layout.screen_main) @WithModule(MainScreen.Module.class)
public class MainScreen extends Path {
    @dagger.Module(injects = MainView.class, addsTo = DaggerConfig.class)
    public static class Module {}

    @Singleton
    public static class Presenter extends ViewPresenter<MainView> {
        @Inject
        public Presenter() {}
    }
}

MainView:

...........
@Inject
MainScreen.Presenter presenter;
...........
@Override protected void onFinishInflate() {
    super.onFinishInflate();
    ButterKnife.inject(this);

    final Path[] screens = {
            new SubScreen("1"),
            new SubScreen("2"),
            new SubScreen("3"),
    };

    CustomPagerAdapter customPagerAdapter = new CustomPagerAdapter(getContext(), screens );
    customPagerAdapter .setAdapter(firstRunPagerAdapter);
}
.....

Now, the main part, SubScreen (3 similar screens, that differs only by the parameters we are passing into them => they should adjust views according these parameters)

@Layout(R.layout.screen_subscreen) @WithModule(SubScreen.Module.class)
public class SubScreen extends Path {
    private final String title;
    public SubScreen(String titleParam) {
        title = titleParam;
    }

    @dagger.Module(injects = SubView.class, addsTo = DaggerConfig.class)
    public class Module {
        @Provides
        SubViewMetadata provideSubViewMetadata() {
            return new SubViewMetadata(backgroundColor, title);
        }
    }

    @Singleton
    public static class Presenter extends ViewPresenter<SubView> {

        private String title;

        @Inject
        public Presenter(String title) {
            this.title= title;
        }

        @Override
        protected void onLoad(Bundle savedInstanceState) {
            super.onLoad(savedInstanceState);
            if (!hasView()) {
                return;
            }

            getView().setTitle(subViewMetadata.title);
        }
    }
}

and it's view public class SubView extends FrameLayout {

    @InjectView(R.id.subViewTitleTextView)
    TextView subViewTitleTextView;

    @Inject
    SubScreen.Presenter presenter;

    public SubView(Context context, AttributeSet attrs) {
        super(context, attrs);
        ObjectGraphService.inject(context, this);
    }

    public void setTitle(String title) {
        subViewTitleTextView.setText(title);
    }

    @Override protected void onAttachedToWindow() {....}

    @Override protected void onDetachedFromWindow() {....}
......
}

Custom Pager adapter:

public class CustomPagerAdapter extends PagerAdapter {
    private final Context context;
    private final Path[] screens;

    public CustomPagerAdapter(Context context, Path[] screens) {
        this.context = context;
        this.screens = screens;
    }

    @Override
    public int getCount() {
        return (screens == null)? 0 : screens.length;
    }

    @Override
    public boolean isViewFromObject(View view, Object o) {
        return view.equals(o);
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        Path screen = screens[position];
        MortarScope originalScope = MortarScope.getScope(context);
        MortarScope newChildScope =  originalScope.buildChild().build("tutorialpage" + position);
        Context childContext = newChildScope.createContext(context);
        View newChild = Layouts.createView(childContext, screen);
        container.addView(newChild);
        return newChild;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        View view = ((View) object);
        container.removeView(view);
        MortarScope.getScope(view.getContext()).destroy();
    }
}

The problem statement: it's crashing, as SubView class hasn't been added into list of Injections at the "Layouts.createView(childContext, screen);" moment in the Adapter, and I can't add it by default, because I want to have a @provider of data from SubScreen to SubScreen.Presenter. (I'm using local variable.

If I add SubView.class into list of injections and convert local Screen's variables into static, then I'll have 3 identical pages inside the ViewPager (which is logical, as every next call of the constructor - overrides old static variables).

Any help/ideas? Thanks for your help, Konstantin

Please explain, completely and precisely, what "haven't managed to make it work" means. — CommonsWare, May 26 '15 at 14:04
@CommonsWare hi, it means, that the snippet from above is outdated and doesn't work with current versions of Flow&Mortar, unfortunately — Konstantin Loginov, May 26 '15 at 14:05
i.e. question is mostly how by having a Screen to get a View for this screen. I think that's my biggest issue now. — Konstantin Loginov, May 26 '15 at 14:25
possible duplicate of [Using Flow & Mortar with ViewPager](http://stackoverflow.com/questions/27995917/using-flow-mortar-with-viewpager) — Peter O., Jun 29 '15 at 23:06

score 4 · Accepted Answer · answered Jun 09 '15 at 18:48

Ok, I figured out.

First of all, adding SubView into list of globally injected classes Then modifying SubScreen class:

@Layout(R.layout.screen_subscreen)
public class SubScreen extends Path {
    private static String titleStatic; // Introducing static variable
    private final String title;
    public SubScreen(String titleParam) {
        title = titleParam;
    }

    public void refreshPresenter() {
        titleStatic = title;
    }

    @Singleton
    public static class Presenter extends ViewPresenter<SubView> {

        private String title;

        @Inject
        public Presenter() {
        }

        @Override
        protected void onLoad(Bundle savedInstanceState) {
            super.onLoad(savedInstanceState);
            if (!hasView()) {
                return;
            }

            getView().setTitle(titleStatic);
        }
    }
}

and then in Custom adapter do this changes:

public class CustomPagerAdapter extends PagerAdapter {
    private final Context context;
    private final SubScreen[] screens;

    public CustomPagerAdapter(Context context, SubScreen[] screens) {
        this.context = context;
        this.screens = screens;
    }
    ......
    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        SubScreen screen = screens[position];
        MortarScope originalScope = MortarScope.getScope(context);
        MortarScope newChildScope =  originalScope.buildChild().build("tutorialpage" + position);
        Context childContext = newChildScope.createContext(context);

        screen.refreshPresenter(); // updating the static var with local one!

        View newChild = Layouts.createView(childContext, screen);
        container.addView(newChild);
        return newChild;
    }
    ....
}

I.e. the solution is to keep the local AND static variables in the Screen, if the same screen is going to be reused. And when we inflate the view it - just setting the right value to the static one (that would be used in the Presenter).

I am not sure, that it is the best possible solution, but it works. It would be nice to hear, if it can be improved.

Mortar and Flow libraries vs. ViewPager

1 Answers1