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POProblems with Android Fragment back stack
 

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  1. POProblems with Android Fragment back stack
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    <p>I've got a massive problem with the way the android fragment backstack seems to work and would be most grateful for any help that is offered.</p> <p>Imagine you have 3 Fragments</p> <p><code>[1] [2] [3]</code></p> <p>I want the user to be able to navigate <code>[1] &gt; [2] &gt; [3]</code> but on the way back (pressing back button) <code>[3] &gt; [1]</code>.</p> <p>As I would have imagined this would be accomplished by not calling <code>addToBackStack(..)</code> when creating the transaction that brings fragment <code>[2]</code> into the fragment holder defined in XML.</p> <p>The reality of this seems as though that if I dont want <code>[2]</code> to appear again when user presses back button on <code>[3]</code>, I must not call <code>addToBackStack</code> in the transaction that shows fragment <code>[3]</code>. This seems completely counter-intuitive (perhaps coming from the iOS world).</p> <p>Anyway if i do it this way, when I go from <code>[1] &gt; [2]</code> and press back I arrive back at <code>[1]</code> as expected.</p> <p>If I go <code>[1] &gt; [2] &gt; [3]</code> and then press back I jump back to <code>[1]</code> (as expected). Now the strange behavior happens when I try and jump to <code>[2]</code> again from <code>[1]</code>. First of all <code>[3]</code> is briefly displayed before <code>[2]</code> comes into view. If I press back at this point <code>[3]</code> is displayed, and if I press back once again the app exits.</p> <p>Can anyone help me to understand whats going on here? </p> <p><BR> And here is the layout xml file for my main activity: <BR></p> <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt; &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" &gt; &lt;fragment android:id="@+id/headerFragment" android:layout_width="match_parent" android:layout_height="wrap_content" class="com.fragment_test.FragmentControls" &gt; &lt;!-- Preview: layout=@layout/details --&gt; &lt;/fragment&gt; &lt;FrameLayout android:id="@+id/detailFragment" android:layout_width="match_parent" android:layout_height="fill_parent" /&gt; </code></pre> <p></p> <p><BR> <BR></p> <p><strong>Update</strong> This is the code I'm using to build by nav heirarchy</p> <pre><code> Fragment frag; FragmentTransaction transaction; //Create The first fragment [1], add it to the view, BUT Dont add the transaction to the backstack frag = new Fragment1(); transaction = getSupportFragmentManager().beginTransaction(); transaction.replace(R.id.detailFragment, frag); transaction.commit(); //Create the second [2] fragment, add it to the view and add the transaction that replaces the first fragment to the backstack frag = new Fragment2(); transaction = getSupportFragmentManager().beginTransaction(); transaction.replace(R.id.detailFragment, frag); transaction.addToBackStack(null); transaction.commit(); //Create third fragment, Dont add this transaction to the backstack, because we dont want to go back to [2] frag = new Fragment3(); transaction = getSupportFragmentManager().beginTransaction(); transaction.replace(R.id.detailFragment, frag); transaction.commit(); //END OF SETUP CODE------------------------- //NOW: //Press back once and then issue the following code: frag = new Fragment2(); transaction = getSupportFragmentManager().beginTransaction(); transaction.replace(R.id.detailFragment, frag); transaction.addToBackStack(null); transaction.commit(); //Now press back again and you end up at fragment [3] not [1] </code></pre> <p>Many thanks</p>
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