Question

我在ViewPager中使用Dagger就像波纹管一样。

我的ViewPagerAdapter.java：

    public class ViewPagerAdapter extends FragmentPagerAdapter {
        private final List<Fragment> mFragmentList;
        private final List<String> mFragmentTitleList;
        private final FragmentManager fragmentManager;

        @Inject
        public ViewPagerAdapter(FragmentManager manager) {
            super(manager);
            this.fragmentManager = manager;
            this.mFragmentList = new ArrayList<>();
            this.mFragmentTitleList = new ArrayList<>();
        }

        @Override
        public Fragment getItem(int position) {
            return mFragmentList.get(position);
        }

        @Override
        public int getCount() {
            return mFragmentList.size();
        }

        public void addFragment(Fragment fragment, String title) {
            mFragmentList.add(fragment);
            mFragmentTitleList.add(title);
        }

        @Override
        public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
            super.destroyItem(container, position, object);
            // remove destroyed Fragment from FragmentManager
            if (!mFragmentList.contains(object)) {
                fragmentManager.beginTransaction().remove((Fragment) object).commit();
            }
        }

        @Override
        public int getItemPosition(@NonNull Object object) {
            return POSITION_NONE;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return mFragmentTitleList.get(position);
        }
    }

在MainActvity中，我像下面这样使用：

public class MainActivity extends DaggerAppCompatActivity{
    @Inject
    ViewPagerAdapter viewPagerAdapter;
    private void setupViewPager(ViewPager viewPager) {
        Intent intent = getIntent();
            viewPagerAdapter.addFragment(new WorkTableFragment(), getString(R.string.workTable));
            viewPagerAdapter.addFragment(MouFragment.newInstance(langID, lang), getString(R.string.mou));
            viewPager.setAdapter(viewPagerAdapter);
            tabsMainActivity.setupWithViewPager(viewPager);
            viewPager.setCurrentItem(1);
        }
    }
}

我的classes中的dagger就像下面的波纹管。我的ActivityBuilder：

@Module
public abstract class ActivityBuilder {
    @ContributesAndroidInjector(modules = MainActivityModule.class)
    abstract MainActivity bindMainActivity();

}

还有AppComponent：

@Singleton
@Component(modules = {
        AndroidSupportInjectionModule.class,
        AppModule.class,
        ActivityBuilder.class})
public interface AppComponent extends AndroidInjector<DaggerApplication> {

    void inject(App app);

    @Override
    void inject(DaggerApplication instance);

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

还有AppModule：

@Module
public abstract class AppModule {

    @Binds
    abstract Context provideContext(Application application);

}

还有我的MainActivityModule：

@Module
public abstract class MainActivityModule {

    private static MainActivity mainActivity;

    public MainActivityModule(MainActivity mainActivity) {
        this.mainActivity = mainActivity;
    }

    @Provides
    static MainPresenter provideMainPresenter(MainContract.MainContractView mainView, DataSourcesLocal dataSourcesLocal) {
        return new MainPresenter(mainView, dataSourcesLocal);
    }

    @Provides
    static ViewPagerAdapter provideViewPagerAdapter() {
        return new ViewPagerAdapter(mainActivity.getSupportFragmentManager());
    }

    @Binds
    abstract MainContract.MainContractView provideMainView(MainActivity mainActivity);
}

我的应用程序类：

public class App extends DaggerApplication {
    @Override
    protected AndroidInjector<? extends DaggerApplication> applicationInjector() {
        AppComponent appComponent = DaggerAppComponent
                .builder()
                .application(this)
                .build();
        appComponent.inject(this);
        return appComponent;
    }
}

但是出现以下错误：

java.lang.NullPointerException: Attempt to invoke virtual method 'android.support.v4.app.FragmentManager android.support.v4.app.FragmentActivity.getSupportFragmentManager()' on a null object reference

Answer 1

解决了我的问题：

@Module
public abstract class MainActivityModule {

    @Provides
    static MainPresenter provideMainPresenter(MainContract.MainContractView mainView, DataSourcesLocal dataSourcesLocal) {
        return new MainPresenter(mainView, dataSourcesLocal);
    }

    @Provides
    static ViewPagerAdapter provideViewPagerAdapter(MainActivity mainActivity) {
        return new ViewPagerAdapter(mainActivity.getSupportFragmentManager());
    }

    @Binds
    abstract MainContract.MainContractView provideMainView(MainActivity mainActivity);
}

Answer 2

将您的MainModule更改为：

@Module
public abstract class MainActivityModule {

    @Provides
    static MainPresenter provideMainPresenter(MainContract.MainContractView mainView, DataSourcesLocal dataSourcesLocal) {
        return new MainPresenter(mainView, dataSourcesLocal);
    }

    @Provides
    static ViewPagerAdapter provideViewPagerAdapter(MainActivity mainActivity) {
        return new ViewPagerAdapter(mainActivity.getSupportFragmentManager());
    }

    @Binds
    abstract MainContract.MainContractView provideMainView(MainActivity mainActivity);
}

您不必自己实例化模块：Dagger将为您处理它并提供MainActivity的正确实例。

带FragmentPagerAdapter的匕首-android

2 个答案: