how only keep one instance for each fragment if i navigate many time between this fragment

Question

for Ex.

I have bottom navigation have 4 tab

when I navigate from A-->B then B-->A then A-->B then B-->A THEN press back ---> B - A - B - A

What I want remove this duplicate so if I press back should be B - A then exit app

public class MainActivity extends BaseActivity implements BottomNavigation.OnMenuItemSelectionListener {

private BottomNavigation mBottomNavigation;
private List<Integer> openedTabs = new ArrayList<>();

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

    initializeViewComponents();
}

private void initializeViewComponents() {
    mBottomNavigation = (BottomNavigation) findViewById(R.id.BottomNavigation);
    if (null != mBottomNavigation) {


        if (openedTabs.size() == 0) {
            openedTabs.add(0);
        }
        mBottomNavigation.setDefaultSelectedIndex(0);
        mBottomNavigation.setOnMenuItemClickListener(this);

    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {

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

@Override
public boolean onOptionsItemSelected(MenuItem item) {

    int id = item.getItemId();


    if (id == R.id.menu_contacts_search) {

    }
    return false;
}

@Override
public void onBackPressed() {
    super.onBackPressed();

    if (openedTabs.size() > 0) {
        int lastIndex = openedTabs.size() - 1;
        int beforeTheCurrent = lastIndex - 1;
        if (beforeTheCurrent >= 0) {
            mBottomNavigation.setSelectedIndex(openedTabs.get(beforeTheCurrent), true);
            printLog("OnBackPressed", "Size: " + openedTabs.size() + " ---> LastIndex: " + lastIndex + " ---> Current: " + openedTabs.get(lastIndex) + "Go To: " + openedTabs.get(beforeTheCurrent));
            openedTabs.remove(lastIndex);
        }
    }
}

@Override
public void onMenuItemSelect(@IdRes int i, int i1) {


    openedTabs.add(i1);
    switch (i) {
        case R.id.profile:
            printLog("Item", "profile");
            replaceFragment(new ProfileFragment());
            break;

        case R.id.my_contacts:
            printLog("Item", "my_contacts");
            replaceFragment(new MyContactsFragment());
            break;

        case R.id.requests:
            printLog("Item", "requests");
            replaceFragment(new RequestsFragment());
            break;

        case R.id.settings:
            printLog("Item", "settings");
            replaceFragment(new SettingsFragment());
            break;
    }
}

@Override
public void onMenuItemReselect(@IdRes int i, int i1) {

}

private void replaceFragment(Fragment fragment) {
    FragmentManager manager = getSupportFragmentManager();
    FragmentTransaction transaction = manager.beginTransaction();
    transaction.replace(R.id.fragmentContainer,fragment);
    transaction.addToBackStack(null);
    transaction.commit();
}

}

Yes you can by Retaining the fragment state Look here [**FragmentRetainInstance.**](http://stackoverflow.com/questions/11160412/why-use-fragmentsetretaininstanceboolean) — Sohail Zahid, Jul 13 '16 at 07:28

antonicg · Answer 1 · 2016-07-13T10:27:08.870

You are adding the transaction to the backStack always, so is normal that if you press the button back you get back through the whole navigation the user did.

Maybe you could try to add the transaction to the backStack transaction.addToBackStack(null); only if there aren't the same fragment on it: fragmentManager.findFragmentByTag(TAG).

To use this, you have to assign a different Tag to every DIFFERENT fragment you are replacing:

So, try this:

private void replaceFragment(Fragment fragment, String tag) {
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction transaction = manager.beginTransaction();
transaction.replace(R.id.fragmentContainer,fragment);

if (fragmentManager.findFragmentByTag(tag) == null)
   transaction.addToBackStack(null);

transaction.commit();

And you call this function that way:

switch (i) {
    case R.id.profile:
        printLog("Item", "profile");
        replaceFragment(new ProfileFragment(), "profile");
        break;

    case R.id.my_contacts:
        printLog("Item", "my_contacts");
        replaceFragment(new MyContactsFragment(), "my_contacts");
        break;

    case R.id.requests:
        printLog("Item", "requests");
        replaceFragment(new RequestsFragment(), "requests");
        break;

    case R.id.settings:
        printLog("Item", "settings");
        replaceFragment(new SettingsFragment(), "settings");
        break;

}

what does it means not working? The behaviour is the same that did before? I will try when I have a moment. — antonicg, Jul 14 '16 at 14:12

Lucker10 · Answer 2 · 2016-07-13T07:56:35.097

You actually create a new instance in your onMenuItemSelect(..), and add everyone to backstack. So either remove your addtoBackStack(null) if this fragment-type already exists (so it doesnt get multiple times added to backstack) OR avoid creating new instances everytime the user switches between the tabs, e.g. by saving the fragments in an

Fragment[] myfrags = new Fragment[4]; //4 means count of your different fragments)

or a HashMap with your IdRes as key and the Fragment as Value

how only keep one instance for each fragment if i navigate many time between this fragment

2 Answers2