ViewPager always starts from 0th position

Question

I have a RecyclerView in a Fragment which is in a ViewPager hosted in an Activity. There's two Activities in this project MainActivity which lists items and DetailActivity which shows details about the item chosen in the first activity.

When I move from DetailsActivity to MainActivity I am always take to ViewPager Fragment position 0 which is the first Fragment. How can I restore the fragment position?

Bundle is always empty when I move from DetailActivity to MainActivity.

Here is the full code of the app.

MainActivity

public class MainActivity extends AppCompatActivity {

    private ViewPager mViewPager;
    private static final String LOG = MainActivity.class.getSimpleName();
    private static final String VIEWPAGER_POSITION = "currentItem";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_titles);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        mViewPager = (ViewPager) findViewById(R.id.viewpager);
        setupViewPager(mViewPager);

        TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
        tabLayout.setupWithViewPager(mViewPager);

        if (savedInstanceState != null) {
            int pos = savedInstanceState.getInt(VIEWPAGER_POSITION, 0);
            Log.d(LOG, "onCreate pos: " + pos);
            mViewPager.setCurrentItem(pos);
        } else {
            Log.d(LOG, "onCreate savedInstanceState is null");
        }
    }

    private void setupViewPager(ViewPager viewPager) {
        ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
        adapter.addFragment(new PopularFragment(), getResources().getString(R.string.popularity));
        adapter.addFragment(new RatingFragment(), getResources().getString(R.string.rating));
        adapter.addFragment(new FavoriteFragment().newInstance(), getResources().getString(R.string.favorite));
        viewPager.setAdapter(adapter);
    }

    public static class ViewPagerAdapter extends FragmentStatePagerAdapter {
        private final List<Fragment> mFragmentList = new ArrayList<>();
        private final List<String> mFragmentTitleList = new ArrayList<>();

        public ViewPagerAdapter(FragmentManager manager) {
            super(manager);
        }

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

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onSaveInstanceState(Bundle bundle) {
        super.onSaveInstanceState(bundle);
        int pos = mViewPager.getCurrentItem();
        Log.d(LOG, "onSaveInstanceState pos: " + pos);
        bundle.putInt(VIEWPAGER_POSITION, mViewPager.getCurrentItem());
    }
}

Thanks.

wojciech_maciejewski · Answer 1 · 2016-05-04T08:22:08.510

0

I am shooting, when you go back from DetailActivity, look for Bundle in

this.getIntent().getExtras().getInt(VIEWPAGER_POSITION, 0)

UPDATE:

if you need persist your current position in for example SharedPreferences in onPause and retrieve it in onResume. like:

private static String MY_PAGER_TAG  = "tag_of_shared_vp_position";
    public void onPause(){ 
  super.onPause();
  int pos = getCurrentViewPagerPosition();//custom function, implement it by //yourself
  SharedPreferences sharedPref = this.getPreferences(Context.MODE_PRIVATE);
  SharedPreferences.Editor editor = sharedPref.edit();
  editor.putInt(MY_PAGER_TAG, pos);
  editor.commit();
}

public void onResume(){
  super.onResume();
  SharedPreferences sharedPref = getActivity().getPreferences(Context.MODE_PRIVATE);
  int pos = sharedPref.getInt(MY_PAGER_TAG,0);
  setUpViewPagerOnPosition(pos);
}

edited May 04 '16 at 08:22

answered May 03 '16 at 19:56

wojciech_maciejewski

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I am not using Intents anywhere. – Sudhir Singh Khanger May 03 '16 at 20:00
so how would you like to know which fragment was open when you are returning? put it to intent – wojciech_maciejewski May 03 '16 at 20:02
I want to go back to where I came from aka restore state. For Intent I will have to send ViewPager position from MainActivity to DetailActivity and back to MainActivity. Is that right? Which doesn't make a lot of sense. – Sudhir Singh Khanger May 03 '16 at 20:30
so why do you finish your MainActivity? that is the only option that onCreate should trigger after going back from Detail. Otherwise MainActivity should just trigger onPause and onResume. Maybe there you are clearing something? – wojciech_maciejewski May 04 '16 at 07:54
I am not finishing the MainActivity intentionally. It's being finished on its on. – Sudhir Singh Khanger May 04 '16 at 08:07

score 0 · Accepted Answer · answered May 04 '16 at 18:07

I noticed that if I pressed the physical back button the ViewPager and RecyclerView were properly restored. So I wanted a way to set up button behavior same as onBackPressed(). Answer to which has already been posted in the question Make the “up” button behave like the “back” button on Android.

I made following changes in DetailActivity and my code started working just fine.

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    if (id == android.R.id.home) {
        onBackPressed();
        return true;
    }

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

ViewPager always starts from 0th position

2 Answers2