android - Fragment enters the back stack twice implicitly

Question

I have several Fragment that are outlined like this :

MainActivity that contains a MainFragment and a WebFragment (just a fragment that has a webview inside of it) :

 <FrameLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@android:id/content"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >

        <fragment
            android:id="@+id/main_fragment"
            android:name="com.citylifeapps.cups.MainFragment"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

        <fragment
            android:id="@+id/venue_fragment"
            android:name="com.citylifeapps.cups.WebFragment"
            android:layout_width="match_parent"
            android:layout_height="match_parent" >
        </fragment>

 </FrameLayout>

MainFragment that contains a ListFragment and a MapFragment :

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:map="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <fragment
        android:id="@+id/map_fragment"
        android:name="com.citylifeapps.cups.MapFragment"
        android:layout_width="match_parent"
        android:layout_height="fill_parent" />

    <fragment
        android:id="@id/list_fragment"
        android:name="com.citylifeapps.cups.ListFragment"
        android:layout_width="wrap_content"
        android:layout_height="fill_parent" />

</RelativeLayout>

My problem is the following scenario :

Start the app, MainFragment starts with the Map and List in the same screen
click on a list item, WebFragment opens up
Click back, MainFragment appears - as expected
Click another back - WebFragment is shown again

The last step (4) is the problem. The expected behaviour is that from the MainFragment (step 3), clicking back will close the app as it is the highest in the chain.

I assume I am doing something wrong with the back stack,

I am trying to debug it but it is extremely hard to debug.

Here is the FragmentManager log :

// Step 1

09-16 16:00:15.683: D/FragmentManager(22278):     Op #0: HIDE WebFragment{42037ea8 #4 id=0x7f050082}
09-16 16:00:15.683: D/FragmentManager(22278):     Op #1: SHOW MainFragment{41e678a0 #0 id=0x7f050081}
09-16 16:00:15.733: V/FragmentManager(22278): moveto ACTIVITY_CREATED: MainFragment{41e678a0 #0 id=0x7f050081}
09-16 16:00:15.733: V/FragmentManager(22278): moveto ACTIVITY_CREATED: MapFragment{41e68c60 #1 id=0x7f05002a}
09-16 16:00:15.733: V/FragmentManager(22278): moveto ACTIVITY_CREATED: SupportMapFragment{41e6adc8 #2 id=0x7f050084}
09-16 16:00:15.733: V/FragmentManager(22278): moveto ACTIVITY_CREATED: ListFragment{42058380 #3 id=0x7f05002b}
09-16 16:00:15.733: V/FragmentManager(22278): moveto ACTIVITY_CREATED: WebFragment{42037ea8 #4 id=0x7f050082}
09-16 16:00:15.733: V/FragmentManager(22278): hide: WebFragment{42037ea8 #4 id=0x7f050082}
09-16 16:00:15.733: V/FragmentManager(22278): show: MainFragment{41e678a0 #0 id=0x7f050081}
09-16 16:00:15.733: V/FragmentManager(22278): moveto STARTED: MainFragment{41e678a0 #0 id=0x7f050081}
09-16 16:00:15.733: V/FragmentManager(22278): moveto STARTED: MapFragment{41e68c60 #1 id=0x7f05002a}
09-16 16:00:15.733: V/FragmentManager(22278): moveto STARTED: SupportMapFragment{41e6adc8 #2 id=0x7f050084}
09-16 16:00:15.733: V/FragmentManager(22278): moveto STARTED: ListFragment{42058380 #3 id=0x7f05002b}
09-16 16:00:15.733: V/FragmentManager(22278): moveto STARTED: WebFragment{42037ea8 #4 id=0x7f050082}
09-16 16:00:15.733: V/FragmentManager(22278): moveto RESUMED: MainFragment{41e678a0 #0 id=0x7f050081}
09-16 16:00:15.733: V/FragmentManager(22278): moveto RESUMED: MapFragment{41e68c60 #1 id=0x7f05002a}
09-16 16:00:15.733: V/FragmentManager(22278): moveto RESUMED: SupportMapFragment{41e6adc8 #2 id=0x7f050084}
09-16 16:00:15.743: V/FragmentManager(22278): moveto RESUMED: ListFragment{42058380 #3 id=0x7f05002b}
09-16 16:00:15.743: V/FragmentManager(22278): moveto RESUMED: WebFragment{42037ea8 #4 id=0x7f050082}

// Step 2

09-16 16:00:28.967: D/FragmentManager(22278):     Op #0: SHOW MainFragment{41e678a0 #0 id=0x7f050081}
09-16 16:00:28.967: D/FragmentManager(22278):     Op #1: HIDE WebFragment{42037ea8 #4 id=0x7f050082}
09-16 16:00:28.977: D/FragmentManager(22278):     Op #0: HIDE MainFragment{41e678a0 #0 id=0x7f050081}
09-16 16:00:28.977: D/FragmentManager(22278):     Op #1: SHOW WebFragment{42037ea8 #4 id=0x7f050082}
09-16 16:00:28.977: V/FragmentManager(22278): Bump nesting of MainFragment{41e678a0 #0 id=0x7f050081} to 1
09-16 16:00:28.977: V/FragmentManager(22278): Bump nesting of WebFragment{42037ea8 #4 id=0x7f050082} to 1
09-16 16:00:28.977: V/FragmentManager(22278): show: MainFragment{41e678a0 #0 id=0x7f050081}
09-16 16:00:28.977: V/FragmentManager(22278): hide: WebFragment{42037ea8 #4 id=0x7f050082}
09-16 16:00:28.977: V/FragmentManager(22278): Bump nesting of MainFragment{41e678a0 #0 id=0x7f050081} to 2
09-16 16:00:28.977: V/FragmentManager(22278): Bump nesting of WebFragment{42037ea8 #4 id=0x7f050082} to 2
09-16 16:00:28.977: V/FragmentManager(22278): hide: MainFragment{41e678a0 #0 id=0x7f050081}
09-16 16:00:28.997: V/FragmentManager(22278): show: WebFragment{42037ea8 #4 id=0x7f050082}

// Step 3

09-16 16:00:39.238: D/FragmentManager(22278):     Op #0: HIDE MainFragment{41e678a0 #0 id=0x7f050081}
09-16 16:00:39.238: D/FragmentManager(22278):     Op #1: SHOW WebFragment{42037ea8 #4 id=0x7f050082}
09-16 16:00:39.238: V/FragmentManager(22278): Bump nesting of MainFragment{41e678a0 #0 id=0x7f050081} to 1
09-16 16:00:39.238: V/FragmentManager(22278): Bump nesting of WebFragment{42037ea8 #4 id=0x7f050082} to 1
09-16 16:00:39.238: V/FragmentManager(22278): hide: WebFragment{42037ea8 #4 id=0x7f050082}
09-16 16:00:39.238: V/FragmentManager(22278): show: MainFragment{41e678a0 #0 id=0x7f050081}

// Step 4

09-16 16:00:53.724: D/FragmentManager(22278):     Op #0: SHOW MainFragment{41e678a0 #0 id=0x7f050081}
09-16 16:00:53.724: D/FragmentManager(22278):     Op #1: HIDE WebFragment{42037ea8 #4 id=0x7f050082}
09-16 16:00:53.724: V/FragmentManager(22278): Bump nesting of MainFragment{41e678a0 #0 id=0x7f050081} to 0
09-16 16:00:53.724: V/FragmentManager(22278): Bump nesting of WebFragment{42037ea8 #4 id=0x7f050082} to 0
09-16 16:00:53.724: V/FragmentManager(22278): show: WebFragment{42037ea8 #4 id=0x7f050082}
09-16 16:00:53.724: V/FragmentManager(22278): hide: MainFragment{41e678a0 #0 id=0x7f050081}

I don't understand what's wrong, The only time I add the WebFragment to the back stack is when I click the list item and open it up in step 2. Also I assume that calling super.onBackPressed() pops the back stack as well.

Here is the simplified version of my code :

public class MainActivity extends ActionBarActivity {

    private boolean venueOrMapPageVisible = false;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.main_activity);

        FragmentManager.enableDebugLogging(true);
        getSupportFragmentManager().beginTransaction()
        .hide(getVenueFragment())
        .show(getMainFragment())
        .commit();

    }

    @Override
    public void onBackPressed() {

        overridePendingTransition(R.anim.slide_in_left, R.anim.slide_out_right);
        if (venueOrMapPageVisible) {
            setDrawerIndicatorEnabled(true);
            venueOrMapPageVisible = false;
        }
        super.onBackPressed();

    }



    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if (super.onOptionsItemSelected(item)) {
          return true;
        }

        switch (item.getItemId()) {
        case android.R.id.home:
            if (venueOrMapPageVisible) {
                onBackPressed();
            }
            break;


        return false;
    }



    // called when a venue is clicked
    @Override
    public void onItemClick(JSONObject venue) {

        if (venue != null) {
            String vid = null;
            try {
                vid = venue.getString("key");
            } catch (JSONException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            openVenue(vid);
        }
    }


    private void openVenue(String vid) {
        getVenueFragment().loadUrl(Consts.venueUri(vid));

        MainActivity.this
                .getSupportFragmentManager().beginTransaction().setCustomAnimations(R.anim.slide_in_right, R.anim.slide_out_left, R.anim.slide_in_left, R.anim.slide_out_right)
                .hide(getMainFragment())
                .show(getVenueFragment())
                .addToBackStack(null)
                .commit();
        venueOrMapPageVisible = true;

        // analytics open venue start time (set it only once)
        if (CupsTracker.venueStartTime == 0L) {
            CupsTracker.venueStartTime = System.currentTimeMillis();
        }
    }


    private WebFragment getVenueFragment() {
        return (WebFragment) getSupportFragmentManager().findFragmentById(R.id.venue_fragment);
    }

    private MainFragment getMainFragment() {
        return (MainFragment) getSupportFragmentManager().findFragmentById(R.id.main_fragment);
    }




    public void moveToMapFragment() {
        MapFragment mapFragment = (MapFragment) getSupportFragmentManager().findFragmentById(R.id.map_fragment);
        ListFragment listFragment = (ListFragment) getSupportFragmentManager().findFragmentById(R.id.list_fragment);
        getSupportFragmentManager()
        .beginTransaction()
        .setCustomAnimations(R.anim.slide_in_right, R.anim.slide_out_left, R.anim.slide_in_left, R.anim.slide_out_right)
        .hide(listFragment)
        .addToBackStack(null)
        .commit();
        mapFragment.getView().setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
        venueOrMapPageVisible = true;

    }

}

I suspect that since the MainActivity layout file contains both the MainFragment and WebFragment, when it is inflated, WebFragment somehow implicitly added to the back stack or something. Is it possible ?

android - Fragment enters the back stack twice implicitly

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