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PONull FragmentTransaction being passed to TabListener.onTabSelected()
 

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    <p>I'm adding navigation tabs to an action bar using the sample code provided here: <a href="http://developer.android.com/guide/topics/ui/actionbar.html">http://developer.android.com/guide/topics/ui/actionbar.html</a> I'm using ActionBarSherlock.</p> <p>My TabListener is copied directly from the docs.</p> <pre><code> public static class TabListener&lt;T extends Fragment&gt; implements ActionBar.TabListener { private Fragment mFragment; private final Activity mActivity; private final String mTag; private final Class&lt;T&gt; mClass; /** Constructor used each time a new tab is created. * @param activity The host Activity, used to instantiate the fragment * @param tag The identifier tag for the fragment * @param clz The fragment's Class, used to instantiate the fragment */ public TabListener(Activity activity, String tag, Class&lt;T&gt; clz) { mActivity = activity; mTag = tag; mClass = clz; } /* The following are each of the ActionBar.TabListener callbacks */ public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) { // Check if the fragment is already initialized if (mFragment == null) { // If not, instantiate and add it to the activity mFragment = Fragment.instantiate(mActivity, mClass.getName()); ft.add(android.R.id.content, mFragment, mTag); } else { // If it exists, simply attach it in order to show it ft.attach(mFragment); } } public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) { if (mFragment != null) { // Detach the fragment, because another one is being attached ft.detach(mFragment); } } public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) { // User selected the already selected tab. Usually do nothing. } } </code></pre> <p>And I set up the listener in my activity:</p> <pre><code> ActionBar.Tab tab = actionBar.newTab(); tab.setText(getString(R.string.TAB_CALC)); tab.setTabListener(new TabListener&lt;StrokeSelectorFragment&gt;(this, "blah", StrokeSelectorFragment.class)); actionBar.addTab(tab); </code></pre> <p>But the app blows up with a null pointer exception because a null FragmentTransaction is being passed to onTabSelected() in the listener. Should I be creating one somewhere?</p> <p>I've been over and over the docs, and I'm pretty confused. Can you see what I've missed?</p>
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    1. COThe sample Activity code in this ActionBarSherlock bug report will help: https://github.com/JakeWharton/ActionBarSherlock/pull/402
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