BottomNavigationView back button behavior should work like the Youtube App but crashes

user_898307 0
Viewed 4015

Steps to reproduce:

  1. Start a new Android project, choose "BottomNavigationView": enter image description here

  2. Replace MainActivity with this:

    class MainActivity : AppCompatActivity() {

private var fragmentIds = ArrayList<Int>()

val fragmentA: FragmentA = FragmentA()
private val fragmentB = FragmentB()
private val fragmentC = FragmentC()

private fun getFragment(fragmentId: Int): Fragment {
    when (fragmentId) {
        R.id.navigation_home -> {
            return fragmentA
        }
        R.id.navigation_dashboard -> {
            return fragmentB
        }
        R.id.navigation_notifications -> {
            return fragmentC
        }
    }
    return fragmentA
}

private fun updateView(fragmentId: Int) {
    var exists = false
    fragmentIds
            .filter { it == fragmentId }
            .forEach { exists = true }

    if (exists) {
        fragmentIds.remove(fragmentId)
        showTabWithoutAddingToBackStack(getFragment(fragmentId))
    } else {
        fragmentIds.add(fragmentId)
        showTab(getFragment(fragmentId))
    }
}

private val onNavigationItemClicked = BottomNavigationView.OnNavigationItemSelectedListener { item ->
    when (item.itemId) {
        R.id.navigation_home -> {
            updateView(R.id.navigation_home)
            return@OnNavigationItemSelectedListener true
        }
        R.id.navigation_dashboard -> {
            updateView(R.id.navigation_dashboard)
            return@OnNavigationItemSelectedListener true
        }
        R.id.navigation_notifications -> {
            updateView(R.id.navigation_notifications)
            return@OnNavigationItemSelectedListener true
        }
    }
    false
}

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    showTabWithoutAddingToBackStack(fragmentA)

    navigation.setOnNavigationItemSelectedListener(onNavigationItemClicked)

}

private fun showTab(fragment: Fragment) {
    supportFragmentManager
            .beginTransaction()
            .replace(R.id.main_container, fragment, fragment::class.java.simpleName)
            .addToBackStack(fragment::class.java.simpleName)
            .commit()
}

fun showTabWithoutAddingToBackStack(fragment: Fragment) {
    supportFragmentManager
            .beginTransaction()
            .replace(R.id.main_container, fragment, fragment::class.java.simpleName)
            .commit()
}

fun setBottomTab(id: Int) {
    navigation.setOnNavigationItemSelectedListener(null)
    navigation.selectedItemId = id
    // currentTab = id
    navigation.setOnNavigationItemSelectedListener(onNavigationItemClicked)
}
}

  3. Create 3 new classes, FragmentA, FragmentB and FragmentC:

    class FragmentA : Fragment() {

override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
    setHasOptionsMenu(true)
    return inflater.inflate(R.layout.fragment_a, container, false)
}

override fun onResume() {
    super.onResume()
    val act = activity as MainActivity
    act.setBottomTab(R.id.navigation_home)
}
}

with this xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Fragment A" />
</LinearLayout>
  1. Start the app
  2. Press "Dashboard" - Fragment B is shown
  3. Press "Notifications" - Fragment C is shown
  4. Press "Dashboard" - Fragment B is shown
  5. Press "Home" - Fragment A is shown
  6. Press Back button - Fragment B is shown
  7. Press Back button - Fragment C should be shown - App Crashes
  8. Press Back button - Fragment A should be shown - App is crashed
  9. Press Back button - App shuts down. - App is crashed

Here is a video that demonstrates above steps

Stacktrace:

12-06 12:58:35.899 25903-25903/com.example.jimclermonts.bottomnavigationview E/InputEventSender: Exception dispatching finished signal.
12-06 12:58:35.900 25903-25903/com.example.jimclermonts.bottomnavigationview E/MessageQueue-JNI: Exception in MessageQueue callback: handleReceiveCallback
12-06 12:58:35.912 25903-25903/com.example.jimclermonts.bottomnavigationview E/MessageQueue-JNI: java.lang.**IllegalStateException: Fragment already added**: FragmentB{3aac1d9 #1 id=0x7f080059 FragmentB}
                                                                                                     at android.support.v4.app.FragmentManagerImpl.addFragment(FragmentManager.java:1882)
                                                                                                     at android.support.v4.app.BackStackRecord.executePopOps(BackStackRecord.java:825)
                                                                                                     at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2577)
                                                                                                     at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2367)
                                                                                                     at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2322)
                                                                                                     at android.support.v4.app.FragmentManagerImpl.popBackStackImmediate(FragmentManager.java:851)
                                                                                                     at android.support.v4.app.FragmentManagerImpl.popBackStackImmediate(FragmentManager.java:794)
                                                                                                     at android.support.v4.app.FragmentActivity.onBackPressed(FragmentActivity.java:174)
bottomnavigationview android
5 Answers

Hello Please check this I made this and working fine. you can check this. https://github.com/sandeshsk/BackStackFragmentRedirectsToHome

Please update if there is any issue.

This is a method which assigns fragment

public void addFragment(FragmentManager fragmentManager,
                               Fragment fragment,
                               int containerId,boolean isFromHome){

    fragmentManager.popBackStack(null,FragmentManager.POP_BACK_STACK_INCLUSIVE);

    FragmentTransaction fragmentTransaction=fragmentManager.beginTransaction();
    if(isFromHome){
        fragmentTransaction.replace(containerId,fragment);
    }else{
        fragmentTransaction.add(new HomeFragment(),"Home");
        fragmentTransaction.addToBackStack("Home");
    }
    fragmentTransaction.replace(containerId,fragment).commit();

}

This is your navigation item listener

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

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()) {
            case R.id.navigation_home:
              if (getSupportFragmentManager().getBackStackEntryCount() == 0) {
                    addFragment(getSupportFragmentManager(), new HomeFragment(), R.id.frame, true);
                }else{
                    getSupportFragmentManager().popBackStack();
                }
                return true;
            case R.id.navigation_dashboard:
                addFragment(getSupportFragmentManager(),new DashboardFragment(),R.id.frame,false);
                return true;
            case R.id.navigation_notifications:
                addFragment(getSupportFragmentManager(),new NotificationFragment(),R.id.frame,false);
                return true;
            case R.id.navigation_setting:
                addFragment(getSupportFragmentManager(),new SettingFragment(),R.id.frame,false);
                return true;
        }
        return false;
    }
};

onBackPressed method

 @Override
public void onBackPressed() {
    if(getSupportFragmentManager().getBackStackEntryCount()>0){
        navigation.setSelectedItemId(R.id.navigation_home);
    }else {
        super.onBackPressed();
    }
}
user_82641480

If you want to go back to all the items on the stack (not only home) like Youtube, try the following code:

BottomNavigationView bottomNavigationView;
FragmentTransaction transaction;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    bottomNavigationView = (BottomNavigationView) findViewById(R.id.navigation);

    bottomNavigationView.setOnNavigationItemSelectedListener
            (new BottomNavigationView.OnNavigationItemSelectedListener() {
                @Override
                public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                    Fragment selectedFragment = null;
                    switch (item.getItemId()) {
                        case R.id.action_item1:
                            selectedFragment = ItemOneFragment.newInstance();
                            break;
                        case R.id.action_item2:
                            selectedFragment = ItemTwoFragment.newInstance();
                            break;
                        case R.id.action_item3:
                            selectedFragment = ItemThreeFragment.newInstance();
                            break;
                        case R.id.action_item4:
                            selectedFragment = ItemFourFragment.newInstance();
                            break;
                        case R.id.action_item5:
                            selectedFragment = ItemFiveFragment.newInstance();
                            break;
                    }
                    transaction = getSupportFragmentManager().beginTransaction();
                    transaction.replace(R.id.frame_layout, selectedFragment);
                    transaction.addToBackStack(null);
                    transaction.commit();
                    return true;
                }
            });

    //Manually displaying the first fragment - one time only
    transaction = getSupportFragmentManager().beginTransaction();
    transaction.replace(R.id.frame_layout, ItemOneFragment.newInstance());
    transaction.commit();

}

@Override
public void onBackPressed() {
    int count = getSupportFragmentManager().getBackStackEntryCount();
    if (count == 0) {
        super.onBackPressed();
    } else {
        int index = ((getSupportFragmentManager().getBackStackEntryCount()) -1);
        getSupportFragmentManager().popBackStack();
        FragmentManager.BackStackEntry backEntry = getSupportFragmentManager().getBackStackEntryAt(index);
        int stackId = backEntry.getId();
        bottomNavigationView.getMenu().getItem(stackId).setChecked(true);
    }
}
user_100207990
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