Getting null pointer exception changing text in fragment programmatically

[dev goku]

Hello there,I'm new to Android ,i Want to change the Text in a fragment programatically .My problem is that I'm getting an error like this- Attempt to invoke virtual method 'int android.os.Bundle.getInt(java.lang.String)' on a null object reference

I'm sending data from this Activity

 navexpListView.setOnChildClickListener(new ExpandableListView.OnChildClickListener(){
            public boolean onChildClick(ExpandableListView parent, View v,
                                        int groupPosition, int childPosition, long id) {

                int  position=childPosition;
                Intent i=new Intent(getBaseContext(),Tab_Activity.class);
                i.putExtra("position_mainActivity",position);
                startActivity(i);
                return true;
            }
        });

to this Tab_Activity

public class Tab_Activity extends AppCompatActivity {

    private Toolbar toolbar;
    private TabLayout tabLayout;
    private ViewPager viewPager;
    private int[] tabIcons = {
            R.drawable.ic_tab_favourite,
            R.drawable.ic_tab_call
    };

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

        toolbar = (Toolbar) findViewById(R.id.tab_toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

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

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

        int pos=getIntent().getIntExtra("position_mainActivity",2);
        Bundle bundle=new Bundle();
        bundle.putInt("to_Fragment",pos);
        TipsFragment s=new TipsFragment();
        s.setArguments(bundle);
    }

and again I'm passing this data to a Fragment,

TipsFragment

public class TipsFragment extends Fragment {

     public TipsFragment() {
        // Required empty public constructor
    }

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

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        Intent intent;
        View view =inflater.inflate(R.layout.fragment_tips, container, false);
        int to_Inflator = this.getArguments().getInt("to_Fragment");//logcat tells me that this is the line the NPE occurs
        TextView v = (TextView) view.findViewById(R.id.tips_Text);
        v.setText(to_Inflator);
        return view;
    }
}

Please any one help me clear this error.

[Tim Moores]

The first things that jumps out is that in line 30/31 of Tab_Activity you're creating a fragment which is then not used - so it will be be garbage-collected quickly. How are you actually using the fragment?

[dev goku]

I'm using this fragment in a Viewpager contained in a Tab Layout

[dev goku]

First I'm going to send a child position of an ExpandablelistView from an Activity to TabActivity,After setting up its Layout the TabActivity(Tablayout with 2 tabs and 2 fragmnets inside viewpager) gonna send the data it got to TipsFragment and it will populate the textview according to the childposition it got and actually i have 2 fragments i posted only one,please forgive me if I didn't give the right info you needed.

[Tim Moores]

I'm using this fragment in a Viewpager contained in a Tab Layout

OK, so there's more code in Tab_Activity which you didn't post? Well, it's hard to tell what's going on without seeing the relevant code bits.

The first thing to try is to call getArguments in the onCreate method rather than the onCreateView method. But that only makes sense if  the fragment is actually being used (as opposed to just being created), and the code you posted doesn't show that part.

[dev goku]

Here's the full code on TabActivity,

package com.bodybuilder.saran.expandablelistview;

import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import java.util.ArrayList;
import java.util.List;

public class Tab_Activity extends AppCompatActivity {

    private Toolbar toolbar;
    private TabLayout tabLayout;
    private ViewPager viewPager;
    private int[] tabIcons = {
            R.drawable.ic_tab_favourite,
            R.drawable.ic_tab_call
    };


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

        toolbar = (Toolbar) findViewById(R.id.tab_toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

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

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

        //DrawerLayout dl=(DrawerLayout)findViewById(R.id.drawer_layout);

        int pos=getIntent().getIntExtra("position_mainActivity",2);
        Bundle bundle=new Bundle();
        bundle.putInt("to_fragment",pos);
        TipsFragment s=new TipsFragment();
        s.setArguments(bundle);
        //dl.closeDrawer(Gravity.START);

    }

    private void setupTabIcons() {
        tabLayout.getTabAt(0).setIcon(tabIcons[0]);
        tabLayout.getTabAt(1).setIcon(tabIcons[1]);

    }

    private void setupViewPager(ViewPager viewPager) {
        ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
        adapter.addFrag(new TipsFragment(), "Tips");
        adapter.addFrag(new WorkoutsFragment(), "Workouts");
        viewPager.setAdapter(adapter);
    }

    class ViewPagerAdapter extends FragmentPagerAdapter {
        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 addFrag(Fragment fragment, String title) {
            mFragmentList.add(fragment);
            mFragmentTitleList.add(title);
        }

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

and Thanks for Replying..

[Tim Moores]

It's as I suspected: the fragment to which you add the parameter in lines 45 to 48 is not used. Instead, you create another instance of the fragments in lines 61 and 62 to which you're not adding any parameters. Those are the ones that actually get used in the ViewPager.

[Tim Moores]

By the way, if you have exactly two views (or another small, fixed number of views) between which you want to switch, it would probably be easier to use a ViewFlipper rather than a ViewPager. No need to deal with fragments or adapters that way.

[dev goku]

Tim Moores wrote:It's as I suspected: the fragment to which you add the parameter in lines 45 to 48 is not used. Instead, you create another instance of the fragments in lines 61 and 62 to which you're not adding any parameters. Those are the ones that actually get used in the ViewPager.

How do i do that ?

[dev goku]

Tim Moores wrote:It's as I suspected: the fragment to which you add the parameter in lines 45 to 48 is not used. Instead, you create another instance of the fragments in lines 61 and 62 to which you're not adding any parameters. Those are the ones that actually get used in the ViewPager.

Ah.,It Worked Man as You said,I used the already created Fragment instance now.,It worked great.Thank you for your time..