CODEWITHSUNDEEP
androidandroid-fragmentsandroid-viewpager
Stanislav Bondarenko
Stanislav Bondarenko

Reputation: 77

Viewpager onpageselected return wrong position

I ran into some strange issue, whenever I'm trying to assign position to my textview, it goes very strange with the first and second page, it returns 0 for the first one and 0 for the second one, page three says 1, and whenever I swipe back to page 0 it says 1.

Here is my activity (theabcactivity):

public class theabcactivity extends FragmentActivity {


String[] heabc;
int backColor;
int currentnumber = 0;
private ViewPager mPager;
private PagerAdapter mPagerAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.content_theabcactivity);

    heabc = getResources().getStringArray(R.array.heabc);




    // Instantiate a ViewPager and a PagerAdapter.
    mPager = (ViewPager) findViewById(R.id.pager);
    mPager.setPageTransformer(true, new ZoomOutPageTransformer());
    mPagerAdapter = new 
    ScreenSlidePagerAdapter(getSupportFragmentManager());
    mPager.setAdapter(mPagerAdapter);
    mPager.setCurrentItem(0);
    mPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

        }

        @Override
        public void onPageSelected(int CurPage) {

            currentnumber = CurPage;
                Log.e("CurPage", " " + CurPage);
        }

        @Override
        public void onPageScrollStateChanged(int state) {
        }
    });
}


private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {
    public ScreenSlidePagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        Random rnd = new Random();
        backColor = Color.argb(40, rnd.nextInt(256), rnd.nextInt(256), rnd.nextInt(256));
        return new theabc();
    }
    @Override
    public int getCount() {
        return heabc.length;
    }
}
    }

Here I'm assigning the currentnumber = CurPage;, that I reuse later on at my fragment.

Fragment code (theabc):

public class theabc extends Fragment {

TextView itemscount;
String [] heabc;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    ViewGroup rootView = (ViewGroup) inflater.inflate(
            R.layout.theabc, container, false);

    LinearLayout contentll = (LinearLayout)rootView.findViewById(R.id.content);

    heabc = getResources().getStringArray(R.array.heabc);
    itemscount = (TextView)rootView.findViewById(R.id.itemcount);


    theabcactivity abcact = (theabcactivity) getActivity();
    contentll.setBackgroundColor(abcact.backColor);


    itemscount.setText(String.valueOf(abcact.currentnumber));
    Log.e("www", "current number value" + abcact.currentnumber);






    return rootView;
}


    }

One other thing i've noticed that whenever this activity opens up, it loads the fragment two times as I'm receiving the following Log:

E/www: current number value0
E/www: current number value0

It leads me into conclusion that when Viewpager opens up it loads the first two items, the first one and the second one. How can I solve that it would load the first item as 0, the next one 1 and so on?

Thanks in advance.

Upvotes: 1

Views: 1455

Answers (1)

azaLiza
azaLiza

Reputation: 37

This is the normal behaviour of the viewPager widget, it first instantiates the first element (which is the current element) then it loads the next element of the list/array to give the scroll activity a smooth animation. I have faced the same issue and solved it by adding a listener to my view pager

mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
            // This is called a lot of times when the user is scrolling
        }

        @Override
        public void onPageSelected(int position) {
            // Check position here to see which page was selected
            Log.i("current pos_page", "\n" + "\t\t" + "current pos of selected page after scroll = " + position );
            display(position);
        }

        @Override
        public void onPageScrollStateChanged(int state) {
            // Called when the scroll state changes (scroll started - ended)
            if ( state == ViewPager.SCROLL_STATE_IDLE) {
                currentPosition = mViewPager.getCurrentItem();
                Log.i("current pos_scrolled", "\n" + "\t\t" + "current pos SCROLLED FINISH = " + currentPosition );
            }
        }
    });

Then I have used the overrided methods of the page change listener to set the current position to the one given by the onPageScrollStateChanged once the animation of scroll is finished.

Finally, i just call the function i created to set the views i'd like to update inside of onPageSelected.

Upvotes: 1

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