Return to a previous Fragment from any Fragment

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Return to a previous Fragment from any Fragment

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I have a main activity in which some fragments are called:

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

    FragmentManager fm = getSupportFragmentManager();
    FragmentTransaction ft = fm.beginTransaction();

    FragmentUm fragment_um = new FragmentUm();
    ft.add(R.id.fragment, fragment_um).commit();
}

When I load the fragment_um in this Activity I have a RecyclerView where I click on an item that can direct me to the activity_detalhes or call the fragment_dois:

FragmentManager fm = getFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
FragmentDois fragment_dois = new FragmentDois();

ft.addToBackStack(null);
ft.replace(R.id.fragment, fragment_dois).commit();

When loading the fragment_dois I have a RecyclerView which when clicking on an item in the list can direct me to the fragment_tres or to the activity_detalhes. The fragment_tres I have the same situation.

No manifest the main activity is configured to show the home button in the toolbar:

android:parentActivityName=".MainActivity"

However, if you have fragment_load loaded in activity and click the home button, I can not get back to fragment_um. The same thing happens if you are in fragment_tres and click the home button, I can not get back to the fragment_dois.

I tried to use getFragmentManager().popBackStack() or getFragmentManager().popBackStackImmediate() within onOptionsItemSelected(MenuItem item) but it did not work.

My question is, what do I have to do to get back to the previous fragment from any of them?

I made some changes to the code:

In the main activity I use the onBackPressed () class when I click the home icon, through the onOptionsItemSelected (MenuItem item), go back to the previous fragment:

@Override
public void onBackPressed(){
    FragmentManager fm = getSupportFragmentManager();
    if (fm.getBackStackEntryCount() > 0) {
        fm.popBackStack();
    }
}

I removed the manifest I mentioned earlier from the manifest. In the fragmented onViewCreated I implemented this code to programmatically show the home icon in ActionBar. In fragment 1 it becomes false and in the others true:

ActionBar actionbar=((AppCompatActivity)getActivity()).getSupportActionBar();
    actionbar.setDisplayHomeAsUpEnabled(true);

It is working, however it is showing an alert that getSupportActionBar and setDisplayHomeAsUpEnabled can generate a NullPointerException. Can you solve this?

android android-fragment

asked by anonymous 29.04.2018 / 16:11

2 answers

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score 0 · Answer 1

Apparently you're right, instead of using getFragmentManager().popBackStack() and getFragmentManager().popBackStackImmediate() within onOptionsItemSelected(MenuItem item) , use getActivity().getFragmentManager().popBackStack() , this solution worked in question Manage back button between fragments

But this function is to be used in ActionBar and not in the Home button.

score 0 · Answer 2

I do not know if this is the most correct way of solving the problem I pointed out, but I solved it as follows:

In fragments it includes:

@Override
public void onAttach(Context context) {

    super.onAttach(context);

    if (context instanceof Activity){
        mActivity =(Activity) context;
    }
}

public static AppCompatActivity getAppCompActivity(Context context) {
    if (context == null)
        return null;
    if (context instanceof AppCompatActivity) {
        return (AppCompatActivity) context;
    }
    return null;
}

And still in the fragments in onViewCreated:

@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

    ActionBar actionBar = getAppCompActivity(mActivity).getSupportActionBar();
    if (actionBar != null) {
        actionBar.setDisplayHomeAsUpEnabled(true);
    }

}

In MainActivity

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();

    if (id == android.R.id.home){
        onBackPressed();
    }
}

@Override
public void onBackPressed(){
    FragmentManager fm = getSupportFragmentManager();
    if (fm.getBackStackEntryCount() > 0) {
        fm.popBackStack();
    } else {
        super.onBackPressed();
    }
}

I get back among the fragments and I no longer have NullPointerException alert. Maybe they still have improvements, but at the moment it has met my needs.