CODEWITHSUNDEEP
androidandroid-fragments
Filip Luchianenco
Filip Luchianenco

Reputation: 7012

In Fragment on back button pressed Activity is blank

I have an Activity and many fragments inflated in same FrameLayout

<FrameLayout
    android:id="@+id/content_frame"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

example: mainActivity > any fragment (press back button) > activity is blank.

In onCreate:

layout = (FrameLayout)findViewById(R.id.content_frame);
layout.setVisibility(View.GONE);

When I start a fragment:

FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.content_frame, profileFragment);
ft.addToBackStack(null);
ft.commit();
layout.setVisibility(View.VISIBLE);

I suppose I need to make the frameLayout's visibility GONE again on back pressed, but how do I do this?

I tried onBackPressed and set layout.setVisibility(View.GONE); but I cannot go back through fragments, as I go directly to main page.

Upvotes: 81

Views: 84841

Answers (13)

Nirali Pandya
Nirali Pandya

Reputation: 44

Just Comment or Remove transaction.addToBackStack(null) in your code.Below is code to change fragment in kotlin.

fun ChangeFragment(activity: MainActivity, fragment: Fragment) {

    val transaction: FragmentTransaction =
        activity.getSupportFragmentManager().beginTransaction()
        transaction.replace(R.id.tabLayoutContainer, fragment)
        transaction.commit()
}

Upvotes: 0

Shamsul Arefin
Shamsul Arefin

Reputation: 1917

If you have scenario like me where a list fragment opens another details fragment, and on back press you first need to show the list fragment and then get out the whole activity then, addToBackStack for all the fragment transactions. and then on the activity, do like this (courtesy: @JRomero's answer, @MSaudi's comment)

@Override
public void onBackPressed() {
    int fragments = getFragmentManager().getBackStackEntryCount();
    if (fragments == 1) { 
        // make layout invisible since last fragment will be removed
    }
    super.onBackPressed();
}

Upvotes: 0

Filip Luchianenco
Filip Luchianenco

Reputation: 7012

I still could not fix the issue through getBackStackEntryCount() and I solved my issue by making the main page a fragment too, so in the end I have an activity with a FrameLayout only; and all other fragments including the main page I inflate into that layout. This solved my issue.

Upvotes: 1

Jimmy Johnson
Jimmy Johnson

Reputation: 9

I had the same problem when dealing with Firebase's Ui Login screen. When back button was pressed it left a blank screen.

To solve the problem I just called finish() in my onStop() method for said Activity. Worked like a charm.

Upvotes: 0

Sileria
Sileria

Reputation: 15612

Just don't add the first fragment to back stack

Here is the Kotlin code that worked for me.

    val ft = supportFragmentManager.beginTransaction().replace(container, frag)
    if (!supportFragmentManager.fragments.isEmpty()) ft.addToBackStack(null)
    ft.commit()

Upvotes: 5

Goodlife
Goodlife

Reputation: 3922

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    }
    else {
        int fragments = getSupportFragmentManager().getBackStackEntryCount();
        if (fragments == 1) {
            finish();
        } else if (getFragmentManager().getBackStackEntryCount() > 1) {
            getFragmentManager().popBackStack();
        } else {
            super.onBackPressed();
        }
    }
}

To add a fragment 

 getSupportFragmentManager().beginTransaction()
                .replace(R.id.layout_main, dashboardFragment, getString(R.string.title_dashboard))
                .addToBackStack(getString(R.string.title_dashboard))
                .commit();

Upvotes: 47

Sampath Kumar
Sampath Kumar

Reputation: 4463

If you have more than one fragment been used in the activity or even if you have only one fragment then the first fragment should not have addToBackStack defined. Since this allows back navigation and prior to this fragment the empty activity layout will be displayed.

 // fragmentTransaction.addToBackStack() // dont include this for your first fragment.

But for the other fragment you need to have this defined otherwise the back will not navigate to earlier screen (fragment) instead the application might shutdown.

Upvotes: 164

Edgar Sousa
Edgar Sousa

Reputation: 221

If you want to track by the fragments you should override the onBackPressed method, like this

public void onBackPressed() { 
   if (getFragmentManager().getBackStackEntryCount() == 1) {
        finish();
   } else {
        super.onBackPressed();
   }
}

Upvotes: 22

Mehdi Dehghani
Mehdi Dehghani

Reputation: 11601

Almost same as Goodlife's answer, but in Xamarin.Android way:

Load fragment (I wrote helper method for that, but it's not necessary):

public void LoadFragment(Activity activity, Fragment fragment, string fragmentTitle = "")
{
    var fragmentManager = activity.FragmentManager;
    var fragmentTransaction = fragmentManager.BeginTransaction();

    fragmentTransaction.Replace(Resource.Id.mainContainer, fragment);
    fragmentTransaction.AddToBackStack(fragmentTitle);

    fragmentTransaction.Commit();
}

Back button (in MainActivity):

public override void OnBackPressed()
{
    if (isNavDrawerOpen()) drawerLayout.CloseDrawers();
    else
    {
        var backStackEntryCount = FragmentManager.BackStackEntryCount;

        if (backStackEntryCount == 1) Finish();
        else if (backStackEntryCount > 1) FragmentManager.PopBackStack();
        else base.OnBackPressed();
    }
}

And isNavDrawerOpen method:

bool isNavDrawerOpen()
{
    return drawerLayout != null && drawerLayout.IsDrawerOpen(Android.Support.V4.View.GravityCompat.Start);
}

Upvotes: 1

gMale
gMale

Reputation: 17895

On a recent personal project, I solved this by not calling addToBackStack if the stack is empty.

    // don't add the first fragment to the backstack
    // otherwise, pressing back on that fragment will result in a blank screen
    if (fragmentManager.getFragments() != null) {
        transaction.addToBackStack(tag);
    }

Here's my full implementation:

    String tag = String.valueOf(mCurrentSectionId);
    FragmentManager fragmentManager = mActivity.getSupportFragmentManager();
    Fragment fragment = fragmentManager.findFragmentByTag(tag);

    if (fragment != null) {
        // if the fragment exists then no need to create it, just pop back to it so
        // that repeatedly toggling between fragments doesn't create a giant stack
        fragmentManager.popBackStackImmediate(tag, 0);
    } else {
        // at this point, popping back to that fragment didn't happen
        // So create a new one and then show it
        fragment = createFragmentForSection(mCurrentSectionId);

        FragmentTransaction transaction = fragmentManager.beginTransaction()
                .setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN)
                .replace(R.id.main_content, fragment, tag);

        // don't add the first fragment to the backstack
        // otherwise, pressing back on that fragment will result in a blank screen
        if (fragmentManager.getFragments() != null) {
            transaction.addToBackStack(tag);
        }

        transaction.commit();
    }

Upvotes: 2

JRomero
JRomero

Reputation: 4868

You can override onBackPressed and check to see if there is anything on the backstack.

@Override
public void onBackPressed() {
    int fragments = getFragmentManager().getBackStackEntryCount();
    if (fragments == 1) { 
        // make layout invisible since last fragment will be removed
    }
    super.onBackPressed();
}

Upvotes: 15

Jemshit
Jemshit

Reputation: 10038

irscomp's solution works if you want to end activity when back button is pressed on first fragment. But if you want to track all fragments, and go back from one to another in back order, you add all fragments to stack with:

ft.addToBackStack(null);

and then, add this to the end of onCreate() to avoid blank screen in last back pressed; you can use getSupportFragmentManager() or getFragmentManager() depending on your API:

FragmentManager fm = getSupportFragmentManager();
    fm.addOnBackStackChangedListener(new OnBackStackChangedListener() {
        @Override
        public void onBackStackChanged() {
            if(getSupportFragmentManager().getBackStackEntryCount() == 0) finish();             
        }
});

Final words: I don't suggest you to use this solution, because if you go from fragment1 to fragment 2 and vice versa 10 times, when you press back button 10 times it will do it in back order which users will not want it.

Upvotes: 1

irscomp
irscomp

Reputation: 2960

Sorry for the late response.

You don't have to add ft.addToBackStack(null); while adding first fragment.

FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.content_frame, profileFragment);
// ft.addToBackStack(null); --remove this line.
ft.commit();
// ... rest of code

Upvotes: 23

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