Fragment re-created on bottom navigation view item selected

Question

Following is my code for bottom navigation view item selected

bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationI         


        

Answer 1

There are several test cases involved in proper navigation , I am pasting my code with all test cases checked.

FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        switch (item.getItemId()) {
            case R.id.dashboard:
                Fragment fragment;
                fragment = fragmentManager.findFragmentByTag(DashboardFragment.TAG);

                if (fragment == null) {
                    fragment = new DashboardFragment();
                    fragmentTransaction.add(R.id.frame, fragment, DashboardFragment.TAG);
                } else {
                    fragmentTransaction.detach(fragmentManager.getPrimaryNavigationFragment());
                    fragmentTransaction.attach(fragment);
                }
                fragmentTransaction.setPrimaryNavigationFragment(fragment);
                fragmentTransaction.commitNow();
                return true;
            case R.id.expenses:
                fragment = fragmentManager.findFragmentByTag(ExpenseFragment.TAG);
                if (fragment == null) {
                    fragment = new ExpenseFragment();
                    fragmentTransaction.add(R.id.frame, fragment, ExpenseFragment.TAG);
                } else {
                    fragmentTransaction.detach(fragmentManager.getPrimaryNavigationFragment());
                    fragmentTransaction.attach(fragment);
                }
                fragmentTransaction.setPrimaryNavigationFragment(fragment);
                fragmentTransaction.commitNow();
                return true;
            case R.id.vehicle_parts:
                Bundle bundle = new Bundle();
                bundle.putInt("odometer", vehicle.getOdometer());
                bundle.putString("vehicle_id", vehicle.get_id());
                fragment = fragmentManager.findFragmentByTag(PartsFragment.TAG);
                if (fragment == null) {
                    fragment = new PartsFragment();
                    fragment.setArguments(bundle);
                    fragmentTransaction.add(R.id.frame, fragment, PartsFragment.TAG);

                } else {
                    fragmentTransaction.detach(fragmentManager.getPrimaryNavigationFragment());
                    fragmentTransaction.attach(fragment);
                }
                fragmentTransaction.setPrimaryNavigationFragment(fragment);
                fragmentTransaction.commitNow();
                return true;
            case R.id.blog:
                fragment = fragmentManager.findFragmentByTag(BlogFragment.TAG);

                if (fragment == null) {
                    fragment = new BlogFragment();
                    fragmentTransaction.add(R.id.frame, fragment, BlogFragment.TAG);

                } else {
                    fragmentTransaction.detach(fragmentManager.getPrimaryNavigationFragment());
                    fragmentTransaction.attach(fragment);
                }
                fragmentTransaction.setPrimaryNavigationFragment(fragment);
                fragmentTransaction.commitNow();
                return true;
        }
        return false;

Answer 2

I've improved @Viven's answers and written it with Kotlin. My version instantiates fragment only for the first time, hides/shows. I'm new at Kotlin so tell me if I can improve anything.

We need to hold a id to tag map:

private val fragmentTags = hashMapOf(
        R.id.action_home to "home_fragment",
        R.id.action_profile to "profile_fragment"
)

The listener code:

bottomNavigation.run {
    setOnNavigationItemSelectedListener { menuItem ->
        supportFragmentManager.beginTransaction()
                .let { transaction ->
                    // hide current fragment
                    supportFragmentManager.primaryNavigationFragment?.let {
                        // if selected fragment's tag is same, do nothing.
                        if (it.tag == fragmentTags[menuItem.itemId]) {
                            return@setOnNavigationItemSelectedListener true
                        }

                        transaction.hide(it)
                    }

                    var fragment  = supportFragmentManager.findFragmentByTag(fragmentTags[menuItem.itemId])

                    if (fragment == null) {
                        // instantiate fragment for the first time
                        fragment = when(menuItem.itemId) {
                            R.id.action_home -> HomeFragment()
                            R.id.action_profile -> ProfileFragment()
                            else -> null
                        }?.also {
                            // and add it 
                            transaction.add(R.id.frame, it, fragmentTags[menuItem.itemId])
                        }
                    } else {
                        // if it's found show it 
                        transaction.show(fragment)
                    }


                    transaction
                            .setPrimaryNavigationFragment(fragment)
                            .setReorderingAllowed(true)
                }.commitNowAllowingStateLoss()

        return@setOnNavigationItemSelectedListener true
    }

    //bottomNavigation things
    itemIconTintList = null
    selectedItemId = R.id.action_home
}

Answer 3

I solved this problem by adding a ViewPager to which I delegated all my navigation fragments. Its adapter (FragmentPagerAdapter) doesn't recreate the fragments instances when the user navigates through the BotoomNavigationView.

To achieve this, you have to complete 5 easy steps:

1. add a ViewPager to your layout;

2. implement its adapter:

   class YourNavigationViewPagerAdapter(fm: FragmentManager,
                                        private val param1: Int,
                                        private val param2: Int)
   
       : FragmentPagerAdapter(fm) {
   
       override fun getItem(p0: Int) = when(p0) {
           0 -> NavigationFragment1.newInstance(param1, param2)
           1 -> NavigationFragment2.newInstance(param1, param2)
           2 -> NavigationFragment3.newInstance(param1, param2)
           else -> null
       }
   
       override fun getCount() = 3
   }
   

3. don't forget to set the new adapter:

   yourViewPager.adapter = YourNavigationViewPagerAdapter(supportFragmentManager, param1, param2)
   

4. set a OnNavigationItemSelectedListener to your BottomNavigationView like the following:

   yourBottomNavigationView.setOnNavigationItemSelectedListener {
   
       when(it.itemId) {
   
           R.id.yourFirstFragmentMenuItem -> {
               yourViewPager.currentItem = 0
               true
           }
   
           R.id.yourSecondFragmentMenuItem -> {
               yourViewPager.currentItem = 1
               true
           }
   
           R.id.yourThirdFragmentMenuItem -> {
               yourViewPager.currentItem = 2
               true
           }
   
   
           else -> false
       }
   }
   

5. set a OnPageChangeListener to your ViewPager like the following:

   yourViewPager.addOnPageChangeListener(object : 
   ViewPager.OnPageChangeListener {
       override fun onPageScrollStateChanged(p0: Int) {
   
       }
   
       override fun onPageScrolled(p0: Int, p1: Float, p2: Int) {
   
       }
   
       override fun onPageSelected(p0: Int) {
           yourBottomNavigationView.menu.getItem(p0).isChecked = true
       }
   
   })
   

6. enjoy :)

Answer 4

setOnNavigationItemReselectedListener would be a better solution for that

Answer 5

The best way i found to do it.

private void replace_fragment(Fragment fragment) {

        String tag = fragment.getClass().getSimpleName();
        FragmentTransaction tr = getSupportFragmentManager().beginTransaction();

        Fragment curFrag = getSupportFragmentManager().getPrimaryNavigationFragment();
        Fragment cacheFrag = getSupportFragmentManager().findFragmentByTag(tag);

        if (curFrag != null)
            tr.hide(curFrag);

        if (cacheFrag == null) {
            tr.add(R.id.main_frame, fragment, tag);
        } else {
            tr.show(cacheFrag);
            fragment = cacheFrag;
        }

        tr.setPrimaryNavigationFragment(fragment);
        tr.commit();

    }

private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
            = new BottomNavigationView.OnNavigationItemSelectedListener() {

        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {

            switch (item.getItemId()) {
                case R.id.nav_posts:
                    replace_fragment(new PostsFragment());
                    return true;
                case R.id.nav_stores:
                    replace_fragment(new StoresFragment());
                    return true;
                case R.id.nav_chats:
                    replace_fragment(new DiscussionsFragment());
                    return true;
                case R.id.nav_account:
                    replace_fragment(new ProfileFragment());
                    return true;
            }
            return false;
        }
    };

Answer 6

I faced the same problem and finally i i found the solution, you can try this code. it's work for me.

import android.support.annotation.NonNull;
import android.support.design.widget.BottomNavigationView;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MenuItem;
import android.widget.FrameLayout;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
public BottomNavigationView bv;
public home_fragment home;
public account_fragment afrag;
public other_fragment other;
public FrameLayout fr;
android.support.v4.app.Fragment current;
//public FragmentTransaction frt;
    public static int temp=0;
    final Fragment fragment11 = new account_fragment();
    final Fragment fragment22 = new home_fragment();
    final Fragment fragment33 = new other_fragment();
    final FragmentManager fm = getSupportFragmentManager();
    Fragment active = fragment11;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bv=(BottomNavigationView) findViewById(R.id.navigationView);


        fm.beginTransaction().add(R.id.main_frame, fragment33, "3").hide(fragment33).commit();
        fm.beginTransaction().add(R.id.main_frame, fragment22, "2").hide(fragment22).commit();
        fm.beginTransaction().add(R.id.main_frame,fragment11, "1").commit();
bv.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {

            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                switch (item.getItemId()) {
                    case R.id.account:
                        fm.beginTransaction().hide(active).show(fragment11).commit();
                        active = fragment11;
                        return true;

                    case R.id.home1:
                        fm.beginTransaction().hide(active).show(fragment22).commit();
                        active = fragment22;
                        return true;

                    case R.id.other:
                        fm.beginTransaction().hide(active).show(fragment33).commit();
                        active = fragment33;
                        return true;
                }
                return false;
            }
        });
      bv.setOnNavigationItemReselectedListener(new BottomNavigationView.OnNavigationItemReselectedListener() {
          @Override
          public void onNavigationItemReselected(@NonNull MenuItem item) {
              Toast.makeText(MainActivity.this, "Reselected", Toast.LENGTH_SHORT).show();

          }
      });


    }

}