How to update-refresh Fragment in ViewPager by Main Activity programmatically

Question

I'm building an App that use Fragment and a single MainActivity that showing different fragments in the same ViewPager to replicate the behaviour of a typical MVC application.

The problem is that haven't understood how could I update the fragment programmatically to update the ViewPager with the new Fragment changes

For example I have this Fragment that show a chart, (in my intention) when I invoke setFragment(int interval, Point[] snodePoint) from the main, the chart should be updated in ViewPager

public class LineFragment extends Fragment {
    static int interval;
    static Point snodePoints[];


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        final View v = inflater.inflate(R.layout.fragment_linegraph, container,
                false);
        Bundle bundle = this.getArguments();
        ChartConfig cg = bundle.getParcelable("FragmentData");

        snodePoints = cg.getPoints();
        interval= cg.getInterval();
        Line l = new Line();

        for(int i=0; i<snodePoints.length; i++){
          LinePoint p = new LinePoint();
          Point sp=snodePoints[i];
          p.setX(sp.getX());
          p.setY(sp.getY());
          l.addPoint(p)
        }
        l.setColor(getResources().getColor(R.color.green));

        LineGraph li = (LineGraph) v.findViewById(R.id.linegraph);
        li.addLine(l);
        li.setRangeY(0, interval);
        li.setLineToFill(0);

        li.setOnPointClickedListener(new OnPointClickedListener() {

            @Override
            public void onClick(int lineIndex, int pointIndex) {
                // TODO Auto-generated method stub

            }

        });

        return v;
    }
}

In few words I need to

• 1-create a fragment based on the data received by the main activity.
• 2-change the data of the fragment everytime in the main activity happens something like setFragment(...) with new data (generated always by the main).

How could I do this?

The Main Activity with the FragmentAdapter

public class MainActivity extends FragmentActivity {

ViewPager mViewPager;
MyFragmentAdapter mMyFragmentAdapter;

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

    mViewPager = (ViewPager) findViewById(R.id.view_pager);
    final ActionBar bar = this.getActionBar();
    bar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

    LineFragment lineFrag = new LineFragment();
    BarFragment barFrag = new BarFragment();
    PieFragment pieFrag = new PieFragment();

    mMyFragmentAdapter = new MyFragmentAdapter(this, mViewPager);
    mMyFragmentAdapter.addTab(bar.newTab().setText("Line"), LineFragment.class,
            null, lineFrag);
    mMyFragmentAdapter.addTab(bar.newTab().setText("Bar"), BarFragment.class,
            null, barFrag);
    mMyFragmentAdapter.addTab(bar.newTab().setText("Pie"), PieFragment.class,
            null, pieFrag);
    mViewPager.setOffscreenPageLimit(mMyFragmentAdapter.getCount() - 1);
}

public static class MyFragmentAdapter extends FragmentStatePagerAdapter implements
        ActionBar.TabListener, ViewPager.OnPageChangeListener {

    private final MainActivity mContext;
    private final ActionBar mActionBar;
    private final ViewPager mViewPager;
    private final ArrayList<TabInfo> mTabs = new ArrayList<TabInfo>();
    private final ArrayList<Fragment> mFrag = new ArrayList<Fragment>();

    static final class TabInfo {
        private final Class<?> clss;
        private final Bundle args;

        TabInfo(Class<?> _class, Bundle _args) {
            clss = _class;
            args = _args;
        }
    }

    public MyFragmentAdapter(MainActivity activity, ViewPager pager) {
        super(activity.getSupportFragmentManager());
        mContext = activity;
        mActionBar = activity.getActionBar();
        mViewPager = pager;
        mViewPager.setAdapter(this);
        mViewPager.setOnPageChangeListener(this);
    }

    public void addTab(ActionBar.Tab tab, Class<?> clss, Bundle args,
            Fragment frag) {
        TabInfo info = new TabInfo(clss, args);
        tab.setTag(info);
        tab.setTabListener(this);
        mTabs.add(info);
        mFrag.add(frag);
        mActionBar.addTab(tab);
        notifyDataSetChanged();
    }

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

    @Override
    public Fragment getItem(int position) {
        TabInfo info = mTabs.get(position);
        Bundle args = new Bundle();
        ChartConfig cg = new ChartConfig(interval, snodePoint);
        args.putParcelable("FragmentData", cg);
        Fragment f = mFrag.get(position);
        f.setArguments(args);

        return f;
    }

    @Override
    public void onPageScrolled(int position, float positionOffset,
            int positionOffsetPixels) {
    }

    @Override
    public void onPageSelected(int position) {
        mActionBar.setSelectedNavigationItem(position);

    }

    @Override
    public void onPageScrollStateChanged(int state) {
    }

    public void onTabSelected(Tab tab, android.app.FragmentTransaction ft) {
        Object tag = tab.getTag();
        for (int i = 0; i < mTabs.size(); i++) {
            if (mTabs.get(i) == tag) {
                mViewPager.setCurrentItem(i);
            }
        }
    }

    public void onTabUnselected(Tab tab, android.app.FragmentTransaction ft) {
    }

    @Override
    public void onTabReselected(Tab tab, android.app.FragmentTransaction ft) {
    }

}

}

The first time that I create the fragment, the main activity pass successful the parameters to the Fragment through the overrided getItem(int position), but if I try to change the data, also if I try to invoke notifyDataSetChanged() on the adapter mMyFragmentAdapter, nothing happens and the fragments in ViewPager continue to use the same data passed in creation.

EDIT

Following some partial code seen in other question about fragment update I have also tried this

public void update() {
        try{
            LineFragment fragment = 
                      (LineFragment) getSupportFragmentManager().findFragmentByTag(
                                   "android:switcher:"+R.id.view_pager+":0");
                  if(fragment != null)
                  {
                     if(fragment.getView() != null) 
                     {

                        fragment.updateDisplay();
                     }
                  }
        }
        catch(RuntimeException e){
            e.printStackTrace();
        }

    }

Assuming that 0 is the id of the first Fragment-Tab fragment(I'm not sure about this kind of operation), but fragment.updateDisplay(); is not invoked.

Answer 1

In your Adapter override getItemPosition

@Override
public int getItemPosition(Object object) {
    // POSITION_NONE makes it possible to reload the PagerAdapter
    return POSITION_NONE;
}

After that

viewPager.getAdapter().notifyDataSetChanged() 

should work.