FragmentViewPagerAdapter not calling getItem after screen rotation

Question

I have a custom viewPagerAdapter in this activity, when the first launch of the activity (When the main activity starts it with the intent) the pager displays the fragments correctly, but when I rotate the device, the recipe is got from the savedInstantState, and the adapter is started, but the fragments are not displayed and the getItem method doesn't get callled!

Here's the code for the Activity: package com.ameer.bake.activities;

import android.content.Intent;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.NavUtils;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MenuItem;
import android.view.ViewGroup;

import com.ameer.bake.Constants;
import com.ameer.bake.fragments.IngredientsFragment;
import com.ameer.bake.fragments.StepDetailsFragment;
import com.ameer.bake.fragments.StepsFragment;
import com.ameer.bake.R;
import com.ameer.bake.models.Recipe;
import com.ameer.bake.models.Step;
import com.google.gson.Gson;
import com.ogaclejapan.smarttablayout.SmartTabLayout;

public class DetailsActivity extends AppCompatActivity implements StepsFragment.StepCallback{

    private Recipe recipe;
    private IngredientsFragment ingredientsFragment;
    private StepsFragment stepsFragment;



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

    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    if (savedInstanceState != null){
        recipe = new Gson().fromJson(savedInstanceState.getString(Constants.RECIPE), Recipe.class);
        setupViewPager();
    } else if (getIntent().hasExtra(Constants.CURRENT_RECIPE_KEY) ) {
        Gson gson = new Gson();
        recipe = gson.fromJson(getIntent().getStringExtra(Constants.CURRENT_RECIPE_KEY), Recipe.class);
        setTitle(recipe.getName());
        setupViewPager();
    }

}

@Override
public void onStepClicked(Step step) {
    Intent intent = new Intent(DetailsActivity.this, StepActivity.class);
    intent.putExtra(Constants.STEP_KEY, new Gson().toJson(step));
    startActivity(intent);
}

private class RecipePagerAdapter extends FragmentPagerAdapter {
    private static final int NUM_ITEMS = 2;
    private final String[] titles = new String[]{
            getString(R.string.ingredients), getString(R.string.steps)};

    private RecipePagerAdapter(FragmentManager fragmentManager) {
        super(fragmentManager);
        if (ingredientsFragment == null && stepsFragment == null) {
            ingredientsFragment = new IngredientsFragment();
            ingredientsFragment.setIngredients(recipe.getIngredients());
            stepsFragment = new StepsFragment();
            stepsFragment.setSteps(recipe.getSteps());
            stepsFragment.setCallback(DetailsActivity.this);
        }
    }

    // Returns total number of pages
    @Override
    public int getCount() {
        return NUM_ITEMS;
    }

    // Returns the fragment to display for that page
    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0:
                return ingredientsFragment;
            case 1:
                return stepsFragment;
            default:
                return null;
        }
    }

    // Returns the page title for the top indicator
    @Override
    public CharSequence getPageTitle(int position) {
        return titles[position];
    }

}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    if (item.getItemId() == android.R.id.home){
        NavUtils.navigateUpFromSameTask(this);
    }
    return super.onOptionsItemSelected(item);
}

@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
    savedInstanceState.putString(Constants.RECIPE, new Gson().toJson(recipe));
    super.onSaveInstanceState(savedInstanceState);
}

private void setupViewPager(){
    ViewPager vpPager = (ViewPager) findViewById(R.id.vpPager);
    FragmentPagerAdapter pagerAdapter = new RecipePagerAdapter(getSupportFragmentManager());
    vpPager.setAdapter(pagerAdapter);

    SmartTabLayout viewPagerTab = (SmartTabLayout) findViewById(R.id.viewpager_tab);
    viewPagerTab.setViewPager(vpPager);
}

}

Answer 1

The solution was as Pedro Varela mentioned in the comments: "Hope this works. Add setRetainInstance(true); in onCreate of your internal fragments of the view pager "Control whether a fragment instance is retained across Activity re-creation (such as from a configuration change). This can only be used with fragments not in the back stack. If set, the fragment lifecycle will be slightly different when an activity is recreated"" Thanks