Android viewpager setText textView

Question

Sorry for my low level of English, I'll be brief for someone to understand me. I have an activity that has viewpager, this has several inflate layout. On a layout I have a text view. I want to add to this textview textView.setText by a string ("something"); But when I write setText boom! my application stops. Anyone have a solution?

TextView tVNombreMen1;
//

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_local_mostrar_menu);
//      Creando textview y pasandoles variables 

    tVNombreMen1 = (TextView)  findViewById(R.id.tVNombreMenu1);
            tVNombreMen1.setText("aa");

MY CLASS:

   public class Local_tipos_de_menuActivity extends ActionBarActivity {

private String[] opcionesMenu;
private DrawerLayout drawerLayout;
private ListView drawerList;
private ActionBarDrawerToggle drawerToggle;
private CharSequence tituloSeccion;  
private CharSequence tituloApp; 


private ViewPager viewPager;

private LinearLayout page1;
private LinearLayout page2;
private LinearLayout page3;
private LinearLayout page4;
//  variables titulo y descripcion menu
String tituloMenu1 = ("Menu de degustación:");
String descripcionMenu1 = ("Menu compuesto por los platos mas vendidos del  

 local.Debes elegir una bebida 2 entrantes, 2 segundos y un postre o cafe.");
double   precioMenu1      = 10.90;
String tituloMenu2 = ("Menu selecto:");
String descripcionMenu2 = ("Menu compuesto por los platos preferidos del cheff.Debes 

  elegir una bebida 2 entrantes, 2 segundos y un postre o cafe.");
double   precioMenu2      = 16.90;
TextView tVNombreMen1;
  //

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_local_mostrar_menu);
  //      Creando textview y pasandoles variables   

    tVNombreMen1 = (TextView)  findViewById(R.id.tVNombreMenu1);
    tVNombreMen1.setText("aa");
    //      TextView tVDescripcionMenu1 = (TextView)  

       findViewById(R.id.tVDescripcionMenu1);
    //      tVDescripcionMenu1.setText(descripcionMenu1);
    //      TextView tVPrecioMenu1 = (TextView)  

      findViewById(R.id.tVPrecioMenu1);
 //     tVPrecioMenu1.setText("€");


 //     TextView tVNombreMenu2 = (TextView)  findViewById(R.id.tVNombreMenu2);
 //     tVNombreMenu2.setText(tituloMenu2);
 //     TextView tVDescripcionMenu2 = (TextView)       
 findViewById(R.id.tVDescripcionMenu2);
 //     tVDescripcionMenu2.setText(descripcionMenu2);


    //DrawerLayout(menu lateral)
    opcionesMenu = new String[] {"Mi perfil", "Opción 2", "Opción 3","4"};
    drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawerList = (ListView) findViewById(R.id.left_drawer);
    drawerList.setAdapter(new ArrayAdapter<String>(
            getSupportActionBar().getThemedContext(),
            android.R.layout.simple_list_item_1, opcionesMenu));

    drawerList.setOnItemClickListener(new OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view,
                int position, long id) {

            //android.support.v4.app.Fragment fragment = null;

            switch (position) {

                case 0:
                    //fragment = new Fragment1();

                    Intent a = new  

   Intent(Local_tipos_de_menuActivity.this, Local_tipos_de_menuActivity.class);
                       startActivity(a);
                     //abrir activity con una animacion personalizada
                        overridePendingTransition(R.anim.right_in,  
    R.anim.right_out);
                    break;
                case 1:
                    //fragment = new Fragment2();

                    break;
                case 2:
                    //fragment = new Fragment3();

                    break;
                case 3:

                     break;
            }

            android.support.v4.app.FragmentManager fragmentManager = 
                    getSupportFragmentManager();

            fragmentManager.beginTransaction()
            //      .replace(R.id.content_frame, fragment)
                    .commit();

            drawerList.setItemChecked(position, true);

            tituloSeccion = opcionesMenu[position];
            getSupportActionBar().setTitle(tituloSeccion);

            drawerLayout.closeDrawer(drawerList);
        }
    });

    tituloSeccion = getTitle();
    tituloApp = getTitle();

    drawerToggle = new ActionBarDrawerToggle(this, 
            drawerLayout,
            R.drawable.ic_navigation_drawer, 
            R.string.drawer_open,
            R.string.drawer_close) {

        public void onDrawerClosed(View view) {
            getSupportActionBar().setTitle(tituloSeccion);


  ActivityCompat.invalidateOptionsMenu(Local_tipos_de_menuActivity.this);
        }

        public void onDrawerOpened(View drawerView) {
            getSupportActionBar().setTitle(tituloApp);

  ActivityCompat.invalidateOptionsMenu(Local_tipos_de_menuActivity.this);
        }
    };

    drawerLayout.setDrawerListener(drawerToggle);

    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    getSupportActionBar().setHomeButtonEnabled(true);

    //viewpagerindicator viewpager
            viewPager = (ViewPager) findViewById(R.id.pager);
            viewPager.setAdapter(new MainPageAdapter());

            TitlePageIndicator titleIndicator = 
(TitlePageIndicator)findViewById(R.id.indicator);

            //TabPageIndicator titleIndicator = 
(TabPageIndicator)findViewById(R.id.indicator);
            titleIndicator.setViewPager(viewPager);     
            titleIndicator.setOnPageChangeListener(new 
 OnPageChangeListener() {

                @Override
                public void onPageSelected(int position)
                {

                }

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

                }

                @Override
                public void onPageScrollStateChanged(int state)
                {

                }
            });     




}

//ActionBar
@Override
public boolean onCreateOptionsMenu(Menu menu) {

    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {

    if (drawerToggle.onOptionsItemSelected(item)) {
        return true;
    }

    switch(item.getItemId())
    {
        case R.id.action_settings:
            Toast.makeText(this, "Settings", 
 Toast.LENGTH_SHORT).show();;
            break;
        case R.id.action_menu2:
            startActivity(new Intent(this, Menu2Activity.class));
            //abrir activity con una animacion personalizada
            overridePendingTransition(R.anim.left_in, R.anim.left_out);
            break;

        default:
            return super.onOptionsItemSelected(item);
    }

    return true;
}

@Override
public boolean onPrepareOptionsMenu(Menu menu) {

    boolean menuAbierto = drawerLayout.isDrawerOpen(drawerList);
    menu.findItem(R.id.action_atras).setVisible(false);
    if(menuAbierto)
        menu.findItem(R.id.action_menu2).setVisible(false);
    else
        menu.findItem(R.id.action_menu2).setVisible(true);

    return super.onPrepareOptionsMenu(menu);
}

@Override
protected void onPostCreate(Bundle savedInstanceState) {
    super.onPostCreate(savedInstanceState);
    drawerToggle.syncState();
}

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    drawerToggle.onConfigurationChanged(newConfig);
}
//Viewpager
class MainPageAdapter extends PagerAdapter
{

    @Override
    public CharSequence getPageTitle(int position) 
    {
        String title = null;

        switch (position)
        {
        case 0:
            title = "Menu 1";
            break;
        case 1:
            title = "Menu 2";
            break;
        case 2:
            title = "Menu 3";
            break;

        default:
            title = "Menu 4";
            break;
        }
        return title;
    }

    @Override
    public int getCount()
    {
        return 4;
    }

    @Override
    public Object instantiateItem(ViewGroup collection, int position)
    {
        View page = null;
        switch (position)
        {
        case 0:
            if (page1 == null)
            {
                page1 = (LinearLayout) 



LayoutInflater.from(Local_tipos_de_menuActivity.this).inflate(R.layout.page_one_viewpager, null);


            }
            page = page1;
            break;
        case 1:
            if (page2 == null)
            {
                page2 = (LinearLayout) LayoutInflater.from(Local_tipos_de_menuActivity.this).inflate(R.layout.page_two_viewpager, null);


            }
            page = page2;
            break;
        case 2:
            if (page3 == null)
            {
                page3 = (LinearLayout) LayoutInflater.from(Local_tipos_de_menuActivity.this).inflate(R.layout.page_three_viewpager, null);


            }
            page = page3;
            break;
        default:
            if (page4 == null)
            {
                page4 = (LinearLayout) LayoutInflater.from(Local_tipos_de_menuActivity.this).inflate(R.layout.page_four_viewpager, null);
            }
            page = page4;
            break;
        }

        ((ViewPager) collection).addView(page, 0);

        return page;
    }

    @Override
    public boolean isViewFromObject(View view, Object object)
    {
        return view == object;
    }

    @Override
    public void destroyItem(View collection, int position, Object view)
    {
        ((ViewPager) collection).removeView((View) view);
    }

}

I hope someone can help me because I'm going crazy. I the value of a textview setText be changed by, but being this texview within viewpager I find it impossible. While nothing is impossible in this world, thank you.

Answer 1

Instead of setting text in onCreate of the activity do it in instantiateItem of the adapter. You are getting a null pointer exception because the view you are trying to find in onCreate is not added yet. So try following and let me know if you are facing more problems.

@Override
public Object instantiateItem(ViewGroup collection, int position)
{
    View page = null;
    switch (position)
    {
    case 0:
        if (page1 == null)
        {
            page1 = (LinearLayout)     LayoutInflater.from(Local_tipos_de_menuActivity.this).inflate(R.layout.page_one_viewpager, null);

     //Try below code
     tVNombreMen1 = (TextView)  page1.findViewById(R.id.tVNombreMenu1);
     tVNombreMen1.setText("aa");

        }
        page = page1;
        break;
    case 1:
        if (page2 == null)
        {
            page2 = (LinearLayout) LayoutInflater.from(Local_tipos_de_menuActivity.this).inflate(R.layout.page_two_viewpager, null);


        }
        page = page2;
        break;
    case 2:
        if (page3 == null)
        {
            page3 = (LinearLayout)      LayoutInflater.from(Local_tipos_de_menuActivity.this).inflate(R.layout.page_three_viewpager, null);


        }
        page = page3;
        break;
    default:
        if (page4 == null)
        {
            page4 = (LinearLayout) LayoutInflater.from(Local_tipos_de_menuActivity.this).inflate(R.layout.page_four_viewpager, null);
        }
        page = page4;
        break;
    }

    ((ViewPager) collection).addView(page, 0);

    return page;
}